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TABLE OF CONTENTS:
1. INTRODUCTION
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The broad goal of the Severe Thunderstorm Electrification and Precipitation Study (STEPS) is to achieve a better understanding of the interactions between kinematics, precipitation production, and electrification in severe thunderstorms on the High Plains. Several fundamental processes are still not well understood, but can now be investigated due to technological advances in the proposed instrumentation. There appear to be systematic differences in these processes in different types of storms, and STEPS will focus on understanding these differences.
1.1. Field campaign
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The approach will be to deploy observing systems in a field campaign to perform coordinated measurements of environmental wind and thermodynamic vertical profiles, storm windfields, hydrometeor contents, electric fields, particle charge, lightning, and other electrical activity.
The field phase of STEPS will be conducted for an 8-week period 22 May - 16 July 2000, and it will be based along the Colorado-Kansas border area west of Goodland Kansas and encompassing the climatological position of the dry line.
1.2. Field observing systems
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The field observing systems include:
1.3. Range of storms to be observed
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Severe storms, which by definition produce strong winds, tornadoes, large hail, or flooding and which often produce heavy precipitation or frequent lightning, are a primary concern to weather forecasters and to the public. The spectrum of severe storms exhibits a wide range of electrical activity and precipitation type and amount. In fact, precipitation amount and location relative to airflow have been widely used, with some controversy, to classify supercell storms as Low-Precipitation (LP), Classic or Medium-Precipitation (MP), and Heavy-Precipitation (HP) supercell types. The cause of this variation is poorly understood, particularly toward the LP end of the spectrum. Better understanding of the variations in precipitation formation is key to better understanding of much of the behavior of supercell storms, including mechanisms that influence storm precipitation efficiency, feedback effects between precipitation formation and storm dynamics, and storm conditions responsible for the unusual lightning observed in many supercell storms.
Given the relative rarity of LP supercells, these storms will have the highest priority for focused observations, if they develop. The second highest priority will be storms in which most ground flashes are +CG flashes, because such storms also are relatively infrequent, though less infrequent than LP supercells. To the extent possible all research instruments will be focused on the target storm.
Other types of storms may become of the focus of STEPS observations on days when supercell development is not expected, depending on the availability of observing systems and the need for rest among field crews. Once a storm is selected as a focus of observations, every effort will be made to follow it through as much of its life cycle as is feasible.
The knowledge gained in focused field research studies such as STEPS will have considerable potential to improve forecasts of weather hazards. One important aspect of STEPS will be its close synergism with the Goodland KS Weather Forecast Office.
2. PARTICIPATION BY THE NATIONAL WEATHER SERVICE
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The National Weather Service (NWS) Office, and in particular the Weather Forecast Office (WFO) in Goodland, Kansas (GLD), plans to play an important role in the STEPS 2000 Field Project by providing both personnel and resources to the effort. However, it should be noted that during severe weather operations, the primary mission of the NWS--protection of life and property--must take precedent over STEP activities in the event that resources are insufficient to accommodate both.
2.1. Data collection
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WSR-88D KGLD: The Goodland WSR-88D (KGLD) will be used to collect base velocity and reflectivity data during active storm days in the target area. The WFO will closely monitor the Archive II data collection system during active periods. In addition, the WFO will be receptive to suggestions for changes in Volume Coverage Patterns (VCPs), though VCP 11 (360 degrees, 11 slices every 5 minutes at a resolution of 0.95 degree beam width) is normally activated at the beginning of convective events. Although, we currently have no way of copying Base Data Archive tapes on-site, WFO GLD will be willing to order a copy of an event tape from NCDC following their processing procedure and allow that tape to be "checked-out" in order to give the various projects an opportunity to make copies of the radar data at little cost to them.
Incoming reports: Through the Skywarn, Cooperative Observer, and Warning Coordination programs of the NWS, WFO GLD has built-up a large database of weather spotters, law enforcement officials, cooperative observers, and general public, that provide a stream of weather information into the office during convective events. In addition, the office's toll-free number allows chasers and other mobile observers the opportunity to report ongoing weather. The office will share these reports with the project both in real-time (see role of Communications Coordinator) and post-event. In exchange, data and observations from the STEPS data collection platforms will be relayed to WFO GLD in real-time and post-event to assist in warning operations.
Rapid Scan Operations (RSO): Although a switch to GOES-8 RSO is automatic during SPC watch and severe outlook periods, there may be situations in which the project is in data collection mode and RSO is advantageous while no watch or outlook is in effect. Since operational NWS offices have priority in requesting RSO, WFO GLD will submit the request through NWS channels when requested by the STEPS Operations Director.
2.2. WFO Personnel Roles
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A large number of NWS staff are interested in participating in various roles. The following are positions that STEPS participants should be aware of.
Science and Operations Officer: The WFO Science and Operations Officer (SOO) will act as the primary liaison between STEPS project management and the NWS. This person will help match resources and requests between the two parties, including, but not limited to, requests to use WFO facilities, logistical help, NWS personnel participation, and data collection and communication procedures. Although, some NWS personnel are making their own arrangements to work with individual investigators, the SOO will assist others in matching a volunteer's interests with the project's needs.
Senior Forecaster: The shift Senior Forecaster is responsible for decisions related to STEPS activities during his/her shift. These decisions may include the deployment of a Communications Coordinator (see below), changes to the WSR-88D, requesting RSO on behalf of the experiment, and the termination of STEPS related WFO products/activities due to limited resources during severe weather operations.
Short-term Forecaster: The Short-term Forecaster (STF) shifts at WFO Goodland are normally from 6 AM - 2 PM and 2 PM - 10 PM during the convective season. This position usually makes the warning decisions during severe weather events. It is envisioned that the STF will be the major WFO participant in the morning briefings. This person may or may not be the shift Senior Forecaster.
WFO/STEPS Communications Coordinator: During STEPS operations, the shift Senior Forecaster will have the discretion to activate a WFO/STEPS Communications Coordinator. This person's primary role will be to facilitate the flow of information between the WFO and the STEPS Operations Center on behalf on the WFO. Since this position is above and beyond normal staffing during a severe weather situation, this position may not be filled during all events due to scheduling limitations and personnel availability.
Assisting in Data Collection/Operations: Several meteorologists from WFO GLD, as well as, other NWS offices have expressed interest in participating in data collection and daily operations during the project. As scheduling permits, volunteers from WFO GLD will be freed up to assist project researchers. In addition, volunteers from other NWS offices will be available to provide assistance. Some roles where operational meteorologists could provide support include mobile data collection, nowcasting, and coordination. In most cases, the matching of interests and project researchers will be facilitated by the WFO GLD SOO.
Assisting in Post-Event Research: The availability of local datasets, including archived radar data, should allow continued interaction between operational meteorologists and research meteorologists following the data collection period.
2.3. WFO GLD Conference Room
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The conference room at the WFO will be used for morning briefings, as well as, other project meetings during the period of the experiment. The room can accommodate up to 20 participants and has access to a T1 Internet-connected PC with a LCD projector. In addition, a television and a VCR are available.
We understand that a larger meeting room may be needed at times. One option is the National Guard Armory which is immediately next door to our office. It has several meeting rooms which can accommodate larger groups. Another option is a room of similar size that is available at Butterfly Aviation, the FBO at Goodland. This room might be scheduled for some of the briefings/meetings, in order to keep the traffic level at the NWS office to manageable levels.
Due to product schedules, it is strongly recommended that the morning briefing be started no later than 9:30 AM MDT. This time would allow maximum participation by the short-term forecaster and other members of the WFO staff without conflicting with routine product issuance times.
It is hoped that during "quiet" periods in STEPS data collection activities, interaction between operational forecasters at WFO GLD, as well as, other NWS volunteers, and the STEPS research meteorologists can be facilitated through seminars and other meetings conducted in the WFO conference room. The proximity of the field experiment with a NWS WFO provides a rare opportunity for sharing science from both perspectives.
2.4. Special WFO/STEPS Activities
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Logistical Support: WFO GLD has been, and will continue to provide, limited logistical support.
Product Preparation/Dissemination: Products issued either by WFO Goodland, or by the STEPS Operations Center, may provide valuable input to those adjunct resources, such as stormchasers, off-duty employees, or Skywarn Spotters, who may not have access to the more detailed STEPS information, but still can provide useful data if kept up-to-date as to the goals of that day.
By the experiment's start date, three NOAA Weather Radio transmitters will be operating in or near the STEPS primary target area: Bethune Colorado (162.525 MHz), Wray Colorado (Frequency to be determined), and Gem Kansas ( 162.400 MHz). Limited STEPS information can be made available through these broadcasts; however, once warning operations begin, non-warning related information will likely need to be suspended.
STEPS and Skywarn: Skywarn presentations attract a variety of law enforcement, volunteers, and interested public each Spring. These participants can be recruited to provide valuable STEPS-related truth data in addition to the observations they provide in support of the NWS warning program. If requested, WFO GLD, will be willing to briefly discuss STEPS during the presentations held in and near the target area. Besides introducing residents to the project, these Skywarn meetings can provide a venue for giving attendees information on how to get involved.
3. DAILY SCHEDULE AND CONDUCT OF OPERATIONS
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This section focuses on decision making, observing system coordination, responsibilities, and conduct of daily operations. This includes the daily sequence of events leading up to the start of field operations.
A morning meeting starting at 9:00 am local time will be held on a daily basis at the Goodland Kansas Weather Service Forecast Office. The on-duty Operations Director will moderate this meeting except during the transition from one Operations Center Team to the next. In that case, both the out-going and on-coming Ops Directors will share this duty. This meeting will include a short debriefing of the previous day's operations, a presentation of the convective outlook, followed by reports of the status of the observing facilities. Scientific plans and priorities for the day and a tentative shedule will be established. Depending on the expected weather situation, some facilities may already be in the process of deployment and/or operation for the day. Facility coordinators or their representatives will update their crews on the outcome of the morning meeting.
3.1. Daily Schedule
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The daily schedule will begin with the debriefing, weather briefing, and discussion of possible observing scenarios and scientific priorities for the day's operations. During the discussion period, PIs who want to can offer their opinions about priorities, though a small group or individual may make the final decision. The basic scientific operations plan for the day will be decided at the early morning meeting. An Operations Center Team will then assume responsibility for implementing this plan, under the overall direction of the on-duty Operations Director.
3.1.1 Debriefings/briefings
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Debriefing of previous day's operations: The early morning meeting will start with a short debriefing of the previous day's operations. In the early part of the project, this discussion period will help in identifying and correcting problems that have been encountered. The length of this part of the debriefing will likely decrease as the project continues.
An assessment of the results from the just-completed operations will be made, and modifications to operating procedures based on this recent experience may be discussed. On a weekly basis, progress towards the overall goals of STEPS will also be discussed at this debriefing session. Additional discussions may be scheduled as needed. See Section 5, below.
Morning Forecast Briefing: The weather briefing will include about a 20 min discussion of the days weather as well as a tentative outlook for the following two-to-three days. The briefing will be run by a STEPS forecaster in conjunction with the WFO forecaster assigned for the day. A forecast discussion will also be placed on the Internet, on a phone message, and also perhaps on NOAA Weather Radio.
The briefing will discuss the potential and probable timing of convective events within the STEPS operational region, emphasizing the potential for relatively isolated supercell storms, and more specifically noting the probability of LP type supercells. The probability of a nightime MCS will also be discussed.
The briefing will include a discussion of standard forecast parameters (e.g., thermodynamic instability, vertical wind shear, strength of the CAPE, and convective temperature), a discussion of the potential triggering scenarios for the day (e.g., dry line, cold front, other surface boundaries, and orography), and a discussion of anticipated storm types (e.g., supercell, non-supercell, squall line, MCS, and isolated or non-isolated) and likely cell motions.
This information will also be summarized in the form of a Forecast Matrix, which will quantify the overall potential for convective activity appropriate for the STEPS core observational objectives. Components of the Matrix will include:
The Forecast Matrix will be filled out for both the 1-4pm and the 4-8pm timeframes for the current day, as well as for the subsequent 2-3 days. Input from forecasters other than the designated weather briefers can also be included via the Forecast Matrix.
3.1.2. Planning of research missions
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"Canned" research mission scenarios will be planned in advance. (Detwiler suggests a separate major heading be inserted below, maybe item 7 or 8, with canned mission scenarios.) On a daily basis, following the weather briefing and discussion of facilities' status, there will be a discussion of the best mission scenario given the likely convective developments and available facilities. Beneficial modifications to the canned scenarios will be discussed. The operations director will use the outcome of this discussion to guide the day's operations.
Those investigators not able to attend the debriefing may forward their contributions to the Ops Director or suitable representative, who will summarize these contributions for those present at the debriefing.
3.2. Conduct of field operations and the Operations Center
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An Operations Center Team located at the Ops Center and will have responsibility for implementing the day's scientific plan that was decided upon at the morning meeting. However, the Operations Director will have discrectionary power to deviate from this plan when expected weather conditions don't materialize or when observing system constraints prevent a full implementation of the original plans.
During STEPS operations, either the Operations Director or the Nowcaster will be in communications with the WFO at Goodland. This is needed to facilitate the flow of information between the WFO and the STEPS Operations Center. However, this communications must not interfere with the primary mission of the WFO and can be discontinued at the discretion of the WFO.
The Ops Center will be located in the CSU-CHILL radar van at the Kit Carson County Airport about 3.5 miles south of Burlington CO next to US highway 385.
Operations will be conducted using Universal Time (UT). All of Colorado and the Wallace and Sherman Counties (Goodland is in Sherman County) in Kansas will be in the Mountain Daylight Time (MDT) Zone, where UT = MDT + 6 hours. The rest of Kansas will be on Central Daylight Time (CDT). It may be more convenient to refer to meeting, operations start times, and such in local time since that is the one we live in.
Latitude and longitude will be used to the extent possible, while either VORTAC (VOR/DME) or radar-relative coordinates will be used for aircraft and radar operations. Latitude/longitude are convenient coordinates for mobile units and broad-scale points of interest such as storm cells and cores, but generally it is cumbersome for detailed locations within spatially-distributed objects such as storms to be scanned by radar. However, it is expected that means to transform rapidly from radar-relative to lat/lon coordinates will be available to observing system coordinators to ensure that mobile units and such can be directed unambiguously and quickly to target storms.
3.2.1. Operations Center Team
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Three Operations Center Teams will be assembled from qualified STEPS participants, including both research and NWS operational personnel. Some participants may serve on more than one team, and not necessarily in the same capacity. For example, a mobile unit coordinator on one team might serve as a radar scientist on another team.
Each Operations Team will consist of an Operations Director (OD) and five Observing System Coodinators (OSCs): two research Radar Scientists (one each for the S-Pol and CSU-CHILL research radars), an Aircraft Scientist, a Nowcaster, and a Mobile Unit Coordinator. All the Operations Team will be located at the Ops Center in the CSU-CHILL radar van except for the S-Pol Radar Scientist who will be located at the S-Pol remote radar site.
Operations Director: Three individuals selected from the STEPS investigators will rotate in one-week shifts through the position of daily Operations Director (OD). The OD will be responsible for selecting the target storm and for overseeing the deployment of the observing facilities to obtain an optimum data set for meeting the day's scientific objectives, given the day's weather potential and likely storm activity. Target storm selection will be done in consultation with the OSCs who are in direct communication with the outlying mobile units and aircraft personnel. Assessment of the local weather conditions, scientific suitability of a storm, and the ability of both mobile ground-based units and storm-penetrating aircraft to reach potential target storm(s) will all be important considerations in the storm selection process.
The Ops Center Team will give the highest priority (see the detailed list of observational priorities) to storms that meet scientific criteria and in which coordinated measurements are most likely. This selection process will involve staff in the operations center as well as those mobile ground and aircraft units at remote locations. However, the safety of personnel must take precedence over scientific desirability of any storm targeted for observation.
On days when storms are developing or are forecast to develop within the region with prime radar and lightning mapping system coverage, a suitable storm or region will be chosen by the OD. This selection will be based on radar observations, weather observations available on-site, and input from other facility operators. Storms likely to be relatively isolated and severe will have high priority, with LP supercell storms having the highest priority and storms producing many +CG flashes having the second highest priority.
The Operations Director will have primary responsibility for communicating with the Goodland WFO regarding satellite rapid scan operations (SRO). The WFO will initiate the actual SRO request.
Nowcaster: The Nowcaster will be responsible for keeping the Ops Director updated on changing weather conditions and developing storm scenarios as convection begins to develop close to or within the STEPS observational region. To accomplish this task, the Nowcaster will make use of weather information (such as satellite, radar, surface obs, profilers, and MGLASS soundings) that will be available on the web either from the RAP real-time weather page or the GARP weather system available via MMM/COMET. The Nowcaster is also expected to be in communication with the on-duty forecaster at the Goodland WFO in assessing the near-term weather forecasts during the day's research operations. The Nowcaster will also direct the taking of environmental soundings by the two MGLASS units, and interpreting these soundings. The Nowcaster will ensure that these soundings are taken at the appropriate times (every three hours, starting about noon local time) and locations.
The Nowcasting position may occasionally be filled with volunteer personnel from the Goodland WFO. Nowcasting and mobile unit coordination may be combined into one position, depending on expected weather and personnel resources.
Mobile Unit Coordinator: The Mobile Unit Coordinator will communicate with the outlying mobile weather observation units (mesonet, storm sounding, and photography) to get their impressions of developing convection, storms, and existing storm structures. A photo look-up table will be supplied to the Ops Center and all mobile units to aid in the characterization of storm structures being observed by the mobile units. These mostly visual observations of developing weather and the length of time needed for mobile units to reach potential targets will be passed on to the OD to help in the selection of target storm(s) and observing strategies. The Mobile Unit Coordinator will then help guide mobile units to the target storm(s) selected by the OD.
Communication in the form of guidance will be mostly between the Ops Center coordinator and the mobile unit(s) team leaders in the field rather than with each mobile unit. The team leaders are in the best position to vector their individual units and to decide on the specifics of their sampling strategies. The Ops Center coordinator must be mindful that mobile ballooning crews will be very busy during launches.
The Mobile Unit coordinator will keep all mobile units informed of target storms, radar and aircraft observational strategies, and potentially hazardous weather that may be coming their way. When the Nowcaster and Mobile Unit Coordinator duties are combined into one position in the Ops Center, the highest priority will always be given to communicating information about severe weather potential to the mobile units. Safety of mobile crews will be of utmost importance in their deployment and subsequent operations near potentially hazardous weather.
Aircraft coodinator: This person will be responsible for coordinating the T-28 aircraft penetrations of the targeted storms. The OD will consult with the coordinator about possible storm penetration strategies with due consideration to aircraft safety, ability to reach the target storm, the observed storm structure, and the likely storm evolution.
Radar Scientists (2): The two Radar Scientists will be responsible for interpreting the radar echoes, including polarimetric measurements, and for recommending and implementing proper radar scanning strategies, under the overall direction of the OD. The CHILL Radar Scientist will have primary responsibility for ensuring that the two research radars maintain coordinated volumetric scans of the target storm. The CSU-CHILL and S-Pol scientists will consult in this process and the CHILL scientist will select scan parameters for the CHILL radar. A CHILL technical staff member will have direct control of the radar parameters for the CHILL volumetric scans. The S-Pol Radar Scientist will be located at the remote S-Pol site about 14 miles east-northeast of Idalia CO (one mile north of US highway 36 and 2.5 miles west of the Kansas-Colorado stateline). The CHILL radar scientist will be in direct communication with the S-Pol radar scientist who will be responsible for setting parameters for the S-Pol volumetric scans.
3.2.2. Chief coordinators and representatives for the major
components and observing systems
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The following participants will be responsible for overall coordination and representation of the major components and observing systems. These are oversite duties that go beyond staffing requirements for daily field operations.
Operations Center and the radar scientists: Jay Miller of NCAR/MMM will serve as the chief radar scientist/coordinator and Ops Center manager. As such he or his delegate will ensure that the Ops Center is adequately staffed by project scientists in order that daily operations can be conducted. Additionally when the Radar Facility Manager(s) are not present, he or his delegate will be reponsible for determining the status of the research radars and Ops Center and for reporting this at the morning briefings. In this capacity, the chief radar scientist/coordinator will work closely with the CHILL and S-Pol radar facility representatives in the operation of the radars and Ops Center. Miller will also be responsible for establishing staffing for the radar scientists/coordinators within the Ops Center Teams.
Radar facility representatives: Pat Kennedy of CSU or his delegate will serve as the CHILL radar facility and Ops Center representative. Tammy Weckwerth of NCAR/ATD or her delegate will serve as the S-Pol radar facility representative. The radar facility managers are responsible for ensuring that adequate staffing of the separate radars is provided. They will also be responsible for conveying the day's expected operations plan to any radar facility staff involved in operations, but not present at the briefing.
Aircraft coordination: Andy Detwiler of SDSMT will serve as the chief aircraft coordinator. As such he or his delegate will be reponsible for determining the status of aircraft and reporting this at the morning briefings. The chief aircraft coordinator will also be responsible for conveying the day's expected operations plan on to aircraft crews not present at the briefing. Detwiler will also be responsible for establishing staffing for the aircraft coordinators within the Ops Center Teams.
Aircraft facility representatives: Andy Detwiler will serve as representative for the SDSMT armored T-28. Detwiler will work with the Ops Center Team and other investigators to coordinate aircraft operations with other field observations. He also will be the point of contact between other STEPS investigators and the aircraft crew as well as the contacts for obtaining data from the aircraft for initial comparisons with data from other observing systems. Normally, Detwiler will be physically located with the T-28 which will be hangared at Goodland, or at the Ops Center or the Goodland WFO.
The pilot-in-command of the T-28 aircraft will have full authority to accept or reject requests for particular sampling strategies and trajectories in particular situations.
Forecasting, nowcasting, and mobile unit coordination: Morris Weisman of NCAR/MMM will serve as chief coordinator for forecasting, nowcasting, and mobile units. He or his delegate will assure that appropriate personnel are assigned to the daily forecasting and nowcasting duties, that MGLASS soundings are taken at the appropriate times and locations, and that mobile mesonet, photography, and ballooning units are informed of target storms and observing strategies. The chief mobile coordinator will be responsible for reporting the status of mobile units at the morning briefing and conveying the day's operations plan to mobile unit staff not present at the briefing.
MGLASS representative: Ned Chamberlain of NCAR/ATD will serve as ...
Lightning mapping system representative: Paul Krehbiel of NMIMT will serve as ...
Mobile electrical sounding representative: Don MacGorman and Dave Rust of NSSL will serve on a rotating basis as the representative for the NSSL/OU mobile electrical sounding system. The mobile electrical sounding representative will be responsible for ascertaining and reporting the status of the electrical ballooning facilities at the morning briefing, communicating information from the morning briefing to other balloon crew members, and coordinating with the nowcaster to develop an initial strategy for the day for deployment of the NSSL/OU facility. Either representative can be contacted after the STEPS field program for information concerning data from this facility.
3.3. Operations center layout
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There will be room for six workstation positions, including one to be used as the CHILL engineering display. These are to be placed on three 7-ft tables, two workstations per table. Below is a schematic drawing of these positions, left-to-right as you face the wall along which the tables are placed.
+-------------------WALL -------+-DOOR-+-------------------+
| +---+---+ +---+---+ +---+---+ | |
| | 1 | 2 | | 3 | 4 | | 5 | 6 | ---> To machine room |
| +---+---+ +---+---+ +---+---+ | can accomodate |
| N M A O C E | two additional |
| o o / p H N | workstations |
| w b C s I G | |
| l L | |
+--------------WALL--------------------+-----+-------------+
|
LAN
|
MOCCA van---+---Other (?)
3.3.1. Displays and communications
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S-Pol radar scientist: This radar scientist will be located at the remote radar site and will have access to the S-Pol radar data display and scan optimizer. This scientist will be responsible for interpreting the S-Pol radar data and specifying the detailed scan parameters for S-Pol. This function requires a Zebra display.
The CHILL and S-Pol radar scientists will be responsible for interpreting the radar measurements and setting up optimum radar scan strategies. The CHILL scientist will lead this sub-team of two scientists, and will have communications responsibilities with the S-Pol scientist at the remote radar site.
All displays should have some sort of lat/lon grid overlay capability for going back and forth between radar coordinates and latitude-longitude. Ideally, the displays in the Ops center would have the ability to read off the display using mouse-clicks for the coordinate system best suited for the observing systems and components that position is helping direct. Communication by ground-to-ground VHF radio, cellular phones, and/or regular telephone will be provided to all positions.
(This is the planned local area network between the operations van and the MOCCA trailer. It should be treated as such for planning purposes.) The CHILL operations van and MOCCA will be connected by a 100 Mbit/sec fiber link. There will be an 8 port 10/100 Mbit/sec switch in the MOCCA and a 16 port 10/100 Mbit/sec switch in the operations van. There will be another fiber link to the CHILL radar to pick up the realtime data. CHILL displays are driven via sockets from the real-time system in the radar van.
CSU has a 4300 watt UPS in the ops trailer that runs at ~70% capacity with 4 workstations and 2 uvax's. They also have an 1800 watt unit which could supplement as needed. It would be good if ATD or others planning on using the MOCCA to bring one or two UPS systems for the MOCCA trailer.
3.3.2. Data link from S-Pol to the Ops Center at CSU-CHILL
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The Plains phone company (in Joes CO) will provide a dedicated T1 line from the S-Pol site local network via copper wire with repeaters into Idalia. From there the T1 line will be routed to a juncture with the southern leg maintained by the Century phone company in Burlington. Century will route this T1 line into the Burlington Public Library where the line terminates in routers provided by CSU-CHILL. The Operations Center will also be connected to these routers via land line for T1 Internet service.
The land line will consist of only one T1 channel with a transfer rate of 1.5 Mbit/sec each. The transfer rate for the T1 line from S-Pol to the Burlington Public Library is also 1.5 Mbit/sec. Note that this T1 service will be dedicated to transfer of information between the S-Pol remote site and the Ops Center. This means that the S-Pol remote site will be accessible over the Internet from the Operations Center. At this writing, it is most likely that gif images of some of the S-Pol scans will be made available via the Internet. CSU-CHILL will arrange for this Internet provider service between the Ops center and the rest of the world.
3.3.3. Data link from LMA in Goodland to the Ops center
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NMIMT plans to bring the equipment needed for receiving and displaying real-time NLDN data from satellite links. This equipment will be located at the Ops Center. It also may be possible to set up a wireless ethernet link to the Ops Center from the LMA central computing site near the NWS WFO in Goodland where the LMA data will be mapped in real-time. When NMIMT installs their LMA network communications links on the Goodland tower, they will explore the possibility of placing an antenna high up on the tower to attempt a direct link to the Ops Center.
3.3.4. Radio and phone communications
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CSU will install a VHF radio repeater on a tower in Goodland Kansas. This radio will be used for ground-to-ground communications, with 164.05 MHz receive and 164.70 MHz transmit. Communications is expected to 50 miles from this repeater. As a minimum, the Ops center will need to communicate with the NSSL mobile mesonet team leader, the two MGLASS, the electrical ballooning units, and the S-Pol radar site. Ground-to-air radio will be done on the nominal 123.45 MHz VHF frequency with equipment provided by SDSMT.
NSSL will install a second VHF radio repeater on a tower in Idalia Colorado. This secondary repeater will be used for ground-to-ground communications when the mobile units are beyond the range of the primary repeater at Goodland. The secondary repeater will receive on 163.1 MHz and transmit on 163.435 MHz. The mobile units will choose the appropriate "channel" (transmit/receive combination) for the part of the domain they're in and reception conditions. It is likely that the Idalia repeater will be used when the mobile units are in the northern half of the domain and the Goodland repeater when they are in the southern half of the domain.
Three dial-up phone lines (719 346-6037, 346-6038, and 346-6039) are connected into the Ops Center where a small phone switch will give up to 12 stations access to the phone lines as well as providing intercom capability between stations. Telephone service is also expected into the S-Pol remote radar site. Cell-phones will generally be unreliable for most locations of the mobile units within the STEPS study area.
4. OBSERVATIONAL FACILITIES
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The core observational facilities consisting of an Operations Center, communications, two research radars with both Doppler and polarization capabilities, the operational WSR88D radar at Goodland, the T-28 storm-penetrating aircraft, two environmental sounding units, and a lightning mapping system are expected to operate throughout the entire 8-week period: 22 May through 16 July 2000. The JMRF/OU/NSSL facility is expected to conduct ballooning operations for storm soundings for only seven weeks during 22 May - 9 July, when isolated, supercell-type storms are more likely. The mobile mesonet vehicles will operate from 22 May - 1 July.
Observing systems will be deployed to monitor environmental wind and thermodynamic vertical profiles, storm windfields, hydrometeor contents, electric fields, particle charge, lightning, and other electrical activity.
4.1. Radar systems
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The triple-Doppler radar network consists of two research radars, NCAR/S-Pol near the Kansas-Colorado stateline east-northeast of Idalia, Colorado and CSU-CHILL at the Kit Carson County Airport south of Burlington, Colorado and the NWS WSR-88D located at Goodland (KGLD), Kansas. The two research radars will also provide polarization measurements.
The Ops Center will be located at the CSU-CHILL radar site at the Kit Carson Regional Airport about 3.5 miles south of Burlington on US-385. The S-Pol radar will be located 2 miles east from Idalia CO on US-36, then 3 miles north on US-36/US-385, then 8 miles east on US-36 to Rd 13, and finally 1 mile north on Rd 13 to Rd PP.
Preliminary positions for the two research radars, CHILL and S-Pol. Final positions will be determined once the radars are in place. Latitude and longitude positions:
Latitude and longitude positions of the two research radars, CHILL and S-Pol, as determined by GPS (source Dave Brunkow, CSU/CHILL, and Bob Rilling, NCAR/ATD):
The accompanying tables show the triple-Doppler network baselines and lobes and locations of several landmarks relative to the Goodland WSR-88D radar.
4.1.1.
CSU-CHILL research radar
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The CSU-CHILL (technical specifications) is a transportable 11 cm wavelength, pulsed Doppler weather radar with dual polarization capabilities. The 8.5 m diameter parabolic antenna with a half-power beamwidth of 1.0 degree is housed inside an inflatable radome. Both the main beam and sidelobe radiation patterns at horizontal and vertical polarization are very well matched. The klystron-based dual transmitter systems each have a maximum output power level of ~1.0 MW. The matched dual receivers have noise power levels of ~-115 dBm. Data are available in real time on an interactively-controlled color display system.
The CSU-CHILL multi-parameter radar system uses a dual transmitter/receiver design mated to a high performance antenna. This system configuration achieves isolation values of ~35 dB between the horizontal and vertical polarization channels; both the co- and cross-polar return signals are digitally processed. The radar has a variety of data collection capabilities which can be adjusted to best serve the individual investigator's interests. An overview of the CSU-CHILL system and the procedures for its use are outlined below.
Software - Controllable Radar Parameters: Considerable real time flexibility is available in the operation of the CSU-CHILL system. Transmitter pulse lengths from 0.3 to 1.0 microseconds are available, yielding range resolutions of 45 to 150 meters. Pulse repetition times from 800 to 2000 microseconds may be used to adjust the limits on the radar's unambiguous velocity and range. Both the sequence of transmitter polarizations and the number of received pulses per integration cycle are user controllable.
Data Collection and Recording Capabilities: Scanning of the CHILL antenna is also under interactive computer control with fixed pointing, PPI (full and sector), and RHI modes available. Full "over the top" RHI's are possible. The incoming data stream is handled by a programmable Lassen SP20 signal processor. In real time this device is capable of producing either the standard spectral moments (reflectivity, mean velocity, and spectral width), or complex time series values. Field format data are recorded on 8 mm exabyte cassette tapes. These data may subsequently be converted to Universal Doppler Exchange (UF) format for distribution to users. A host of multi-parameter variables [Zdr, HV(0), dp, and LDR] are also measured by the CSU-CHILL system.
Typical PRFs and scan rates for polarimetric measurements: The CHILL radar usually uses a PRF of 1000 Hz, though 1200-500 are available. At this PRF, the antenna is scanned at 6 deg/sec and 128 samples are used to get reliable polarimetric measurements. The radar can scan at 8 deg/sec with 100-sample integrations for 360-deg surveillance mode or when time is of the essence. Slower scan rates of 4 deg/seg and 196-sample integrations have been used for highly focused scans over limited portions of the storm volume. All these assume an alternating V-H polarization sequence.
A "quick" scan mode will be available which consists of PPI scans at 12 deg/sec using 333 nsec pulses and range integration to give 250 m range samples. This will maintain the polarimetric fluctuations at the levels normally found when using 1 microsec pulses and 150 m range sampling and integrating 128 samples at 6 deg/sec rotation rates (0.8 deg beam spacing). In this mode, however, you gain speed at the expense of signal/noise ratio--about 10 dB loss in minimum dBZe. There is also a reduction in the maximum workable range to about 80 km. The loss in sensitivity and reduced maximum range should not be a major problem since intense, nearby storms are the ones that will normally require faster scanning rates.
| STORM CORE (km) |
PULSE DURATION (nanosec) |
RANGE GATE (m) |
NUMBER of SAMPLES |
ROTATION RATE (deg/sec) |
BEAM SPACING (deg) |
|---|---|---|---|---|---|
| < 50 | 333 | 250 | 64 | 12 | 0.8 |
| 50-90 | 500 | 200 | 90 | 9 | 0.8 |
| 90-150* | 1000 | 150 | 128 | 6 | 0.8 |
| * This is also the normal PPI operating mode with no range integration. When shorter pulse durations are used, range integration is done to achieve the listed range gate spacing. For RHIs the rotation rate could be reduced by a factor of two resulting in a beam spacing of 0.4 deg. | |||||
Experimental polarimetric data: On occassion so as not to interfere with the primary goals of STEPS, some experimental tests will be run to help evaluate the proposed mode to acquire polarimetric measurements with NWS WSR-88D radars. It has been proposed that the NWS radars transmit approximate slant 45 deg and receive H and V backscattered co-polar returns simultaneously. This is done by splitting the transmitted power equally into the H and V channels. Since the backscattered co-polar signal will overwhelm any cross-polar component, the linear depolarization ratio (LDR) cannot be measured in this "hybrid" mode. Measurements of Zdr, phidp, and rhohv from this "hybrid" mode will be compared to those from the standard alternating HV mode. The scans would be focused RHI/PPI ones with data acquired alternately from the two modes as quickly as possible. It is proposed to do this for storms of low priority to STEPS, but may include some events with large phidp (>100 deg).
4.1.2.
NCAR S-Pol research radar
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S-Pol (technical specifications) is a new Doppler and polarization radar developed at NCAR/ATD. The entire radar including generators and operations control area is packaged into six 20 foot, standard-sized sea containers. Site preparation and restoration costs are minimized because the antenna support structure is made from the shipping containers themselves. Although typically a radome is not required, the existing CP-2 inflatable radome system could be used to enclose the entire radar in extreme environments. The pedestal will be able to sufficiently control the exposed antenna in a 50 mph wind.
Additionally, S-Pol uses a high performance modern transmitter, low sidelobe parabolic antenna with high isolation between horizontal and vertical channels, and a modern dual channel receiver. The NCAR-designed VME data system provides numerous computed Doppler velocity and polarization variables. The transmitter is an ASR-9 based unit built by Westinghouse. It uses an air cooled klystron and produces a one Megawatt, one microsecond pulse. The PRF can range from 325 to 1200 pulses per second. The transmit pulse is tapered and filtered for minimum RF interference. The 28 foot reflector is a high-compliance aluminum structure providing -30 dB first sidelobes and at least -35 dB integrated cross-polar isolation.
Polarization switching is done by an NCAR built mechanical switch which provides 49 dB transmit isolation. For alternating H/V pulses, this isolation is comparable to a dual transmitter configuration. A separate receiver for each channel provides 40 dB receive isolation. Dual receivers are required for cross-polar measurements and to enable the low channel dwell times of the mechanical switch.
Pulse pair and dual polarization processing is performed by a NCAR-designed, VME-based Integrated Radar Acquisition system (VIRAQ). The VIRAQ processor uses a dual range 90 dB digital IF system with multiple C44 DSP chips that are controlled by a 486 CPU host running DOS.
PRF and scan rates for polarimetric measurements: The PRF to be used for this study will be 960 Hz at a scan rate of 6 deg/sec. The scan rate can be increased some if the ground clutter filter is not necessary in which case a short pulse mode would be used at faster antenna scan rates. About 100-128 samples are needed to obtain reliable polarimetric measurements. When it is necessary to scan faster, the number of samples that are integrated could be reduced to 80 (40 H and 40 V) or even to 64 (32 H and 32 V). These shorter integration times would degrade the polarimetric measurements, but they would allow faster antenna rotation rates while maintaining a nominal 0.8-1 deg beam spacing.
4.1.3.
NWS WSR-88D operational weather radar
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The WSR-88D radar (hereafter referred to as 88D) will provide continous surveillance scans at a sequence of constant elevation angles of radar reflectivity factor (hereafter referred to as reflectivity) within a 460 km radius of Goodland Kansas. This radar will also measure radial velocities within a 230 km radius. The first 150 km radius is the nominal first-trip range for velocities so that radial velocities are available in the next 80 km only where there is no range folding. The 88D will scan using one of the following Volume Coverage Patterns (VCPs).
VCP-11 and VCP-21 are precipitation modes that use a short radar pulse (nominally 250 m range resolution). Both VCPs include separate surveillance (slow rate of pulsing for a 460 km unambiguous range) and Doppler scans (fast rate of pulsing for a 150 km unambiguous range and high Nyquist or folding velocity exceeding 25 m/s) at the two lowest angles. VCP-11 (VCP-21) consists of 360-deg-in-azimuth scans at 14 (9) elevation angles to obtain 5 (6) minute updates of full volume scans. The lowest five elevation angles are contiguous and common to both VCP-11 and VCP-21. The next two elevation angles for VCP-11 are also contiguous. The remaining steps between elevation angles exceed the nominal radar beamwidth of 0.97 deg, leaving some gaps in the vertical coverage.
VCP-31 is a clear air mode and is used to detect early formation of convective precipitation, air mass discontinuities and to obtain wind profiles. It uses a long pulse transmission at 5 elevation angles to obtain a 10 minute update rate. There are separate surveillance and Doppler scans at the lowest three elevation angles. VCP-32 is the same as VCP-31, except with a short pulse. VCP-31 should have greater sensitivity compared to VCP-32 because of its longer pulse.
4.1.4. Research radar scanning strategies
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The highest priority is for the two research radars to operate in a dual-polarimetric, dual-Doppler radar sampling mode, with both radars performing similar kinds of scanning and using similar integration times to obtain high quality polarimetric and Doppler measurements. The proposed scanning strategy for the two research radars is to perform a ~5-min storm volume scan across azimuthal sectors at a sequence of constant elevation angles (PPIs), followed by a ~1-2 min storm volume scan in the elevation angle direction at a sequence of constant azimuth angles (RHIs). This strategy is motivated by the need to have both broad-scale (PPIs) and fine-scale (RHIs) measurements of storm kinematics and microphysics. The RHIs will be focused on the core of the target storm or within the most important parts such as updrafts, downdrafts, regions of active charging, or other regions with important signatures as determined from radar, aircraft, or electrical measurements. The storm volume scan sequence will proceed by toggling between PPIs and RHIs, repeating this PPI-RHI pair every 6-7 min. Specific placement of the PPIs and RHIs will be determined with the help of the in-the-field scan optimizers and some "canned" scans determined before the start of the field study. The scan optimizers are meant to provide guidance in the age-old compromise between horizontal and vertical coverage (the solid angle that must be scanned), horizontal and vertical spatial resolution (azimuth and elevation angle increments), and time resolution (period to cover the storm volume).
The motivation for toggling between PPI and RHI scans is the need to have fairly high vertical resolution of the storm structure, while also covering the storm sector for Doppler wind synthesis. In many Doppler radar studies, storms have not been scanned adequately in the vertical direction, oftentimes not reaching storm tops or sacrifing the vertical resolution to achieve shorter cycle times for the PPI scans.
The use of focused RHIs should help mitigate these two problems, though only over limited horizontal regions. The derivation of accurate vertical wind profiles has been problematic in many past Doppler radar studies. The RHI scans will also give researchers a much better idea of the detailed vertical structure of storms.
The research radar variables can be readily interpolated from either PPI or RHI scans to regular Cartesion coordinates for wind syntheses and other analyses.
The PPI-RHI sequence will be repeated continuously except when it is not advisable to do so during aircraft penetrations. Surveillance scans from the WSR-88D operational network will be used to keep track of the larger scale development of storms in the STEPS study area. In the event that a reliable way to obtain surveillance scan updates from nearby NWS radars in near real time is not found, the research radars will do the necessary surveillance scans, usually in the lower layers and limited to no more than about a one-minute interruption of the PPI-RHI scan mode.
4.2.
Lightning mapping system
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The lightning mapping system will be deployed over an 80-km diameter area both within and around the triple-Doppler network. It will consist of a) 13 or 14 time-of-arrival stations for mapping the lightning in three spatial dimensions and time (the Lightning Mapping Array, or LMA), b) 10 stations of electric field mill and field change instruments, for measuring the overall charge structure of storms and the amounts and sign of the lightning charge transfer, and c) three `fast' electric field change waveform recording stations for detecting and locating ground strokes and in-cloud discharge events. In addition, we plan to operate our VHF lightning interferometer within the network, which complements the mapping data by providing images fast breakdown streamers along the main lightning channels of intracloud and cloud-to-ground discharges.
The LMA will operate on TV Channel 3 (60-66 MHz), an unused channel in the STEPS project area. The system has operated on this frequency both in Oklahoma and New Mexico. The time of arrival of the peak RF signal is accurately determined during successive 100 microsecond windows that the signal is above a threshold and used to locate the source of impulsive radiation events (Rison et al., Geophys. Rsch. Letters, 3573-3576, 1999). The stations will be linked via high-speed (115 kBaud) wireless modems to a central site situated in an office trailer on the grounds of the NWS station in Goodland. The communications links will be used both to monitor and control the operation of the stations and for real-time processing of some of the data. The primary data recording will be on Digital Audio Tape (DAT) locally at each station, with the tapes being collected at regular intervals during the program, and post-processed for the complete lightning information.
The electric field and field-change instruments will be operated in conjunction with ten of the LMA stations. The field mills measure the total electric field at the ground and will be sampled continuously at a 10 to 50 Hz rate. The field change data will be sampled at a 5 or 10 kHz rate, also continuously, for use in determining the amounts and signs of charge transferred by the lightning discharges. Three of the field change stations will also measure and record fast electric field waveforms (sferics) of the lightning discharges. The fast waveforms will be sampled at up to a 20 MHz rate and recorded on a triggered basis. The sferics waveforms can be used to identify and locate individual strokes to ground as well as rapid in-cloud breakdown events. The electric field data will be GPS time-tagged for accurate time synchronization between stations and with the mapping data.
The lightning interferometer operates at 273 MHz and locates the azimuth and elevation of continuous radiation events with 2 microsecond time resolution in real time. Among other things, the observations valuably complement those of the 3D mapping system by showing the paths of fast streamers along the main channels of both intracloud and cloud-to-ground discharges.
4.3. Mobile ground units
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As storm conditions develop, the STEPS operations center will guide the electrical ballooning facility, mobile mesonet vehicles, and mobile GLASS units to storms that are to be the subject of comprehensive measurements. The mobile surface units may begin moving into position before storms are initiated, if an early start is needed to reach a region of potential storms in time for operations. The target region may change as storm conditions warrant, subject to the limitations on distance imposed by safe driving speeds and road conditions.
Though guidance and coordination of the mobile ballooning and mesonet units will be provided by the STEPS operations center, the final decisions regarding actual positioning and sampling strategies for these units will be made by their respective team leaders in the field, because they will be best able to evaluate local safety issues and other matters pertaining to successful sampling strategies.
The mobile GLASS will be positioned for storm environmental soundings by the Nowcaster/Mobile Unit Coordinator at the Operations Center. Local cloud and storm conditions will be an important consideration when MGLASS is positioned to take undisturbed environmental soundings.
4.3.1.
Environmental sounding units
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Two MGLASS units, staffed by technicians from NCAR/ATD/SSSF, will be available to monitor the evolving thermodynamic and vertical wind shear conditions. MGLASS soundings will be taken both west and east of the target area on all days for which observations are being taken. Soundings will nominally be taken simultaneously at 18, 21 and 00 UTC. On days for which a dry line is evident, the soundings will be taken approximately 30-60 km east and west of the dry line location. On non-dryline days, the MGLASS units will be positioned to best monitor the variability of conditions across the STEPS domain. Soundings will be relaid in real-time to RAP so as to make the soundings and hodographs available to all STEPS participants via the RAP realtime weather page.
Photography: Photography will be taken from the two MGLASS units, which will be located both east and west of the targeted storm regions. These units will be responsible for documenting storm-scale characteristics for storms targeted for intensive observations. Such documentation will be critical for comparing the visual storm characteristics to previously developed conceptual models of LP, Classic and HP supercell types. Time-Lapse will be especially useful for documenting storm characteristics.
If resources, opportunity, and conditions permit, photography may also be taken from the mobile mesonet and ballooning facilities.
4.3.2.
Mobile electrical ballooning facility
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The NSSL/OU mobile balloon facility plans to participate in the STEPS field program for seven weeks, May 22 - July 9, to obtain balloon flights in various regions of storms. The mobile balloon facility will consist of (1) the mobile laboratory, which houses data receivers, voice communication equipment, a GPS tracking system, and a field mill to measure the static electric field, (2) a panel truck to carry an inflated balloon, electric field meters, rawinsondes, miscellaneous supplies, and extra balloons and helium, and (3) a minivan for additional crew members. The crew will have 9-10 members, one to remain available for communication with the operations center and the nowcaster during launch, one to monitor balloon data reception, 5-6 to launch the balloon and instrument train, and two to begin inflating the next balloon. Balloons will be launched from a portable launch tube, which has been used for launches in wind with speeds up to 75 mph (65 knots). Specifications for the balloon indicate a nominal maximum height of 20 km, and the ascent rate relative to still air is typically 5 m/s.
Each flight will carry at least one electric field meter and a rawinsonde. Thirty electric field meters will be available for flights to measure the electric field inside storms. The mobile laboratory will house receivers to acquire data from up to four electric field meters simultaneously. Balloon tracking and standard thermodynamic measurements will be provided by using the NCAR dropsonde system, which can process data from up to four sondes simultaneously. The dropsondes that will be used in STEPS have been modified for use on balloons; each has a full GPS engine to provide reliable tracking. The data produced from each flight are the electric field, pressure, temperature, dew point, horizontal wind speed and direction, ascent rate, time, latitude, longitude, and altitude at approximately 1-s intervals along the balloon track. In addition, the electric field will be measured at the ground during periods of interest.
Up to four soundings will be acquired in various storm-relative locations inside each storm being observed by STEPS, though our expectation is that typically fewer balloon launches will be possible before a storm moves out of range. If possible, sequential soundings will be made from a fixed location as the storm moves, in part because data reception is best when the mobile laboratory remains stationary. However, data can be acquired as the vehicle moves, if necessary either for safety or for targeting another part of the storm. On a few flights, two electric field meters will be flown at least 60 m apart vertically on the same balloon to try to separate spatial changes in the electric field from temporal changes.
The updraft is of particular interest to STEPS and will be the highest priority for balloon flights. Most other regions of storms, including anvils reasonably close to deep convection, also are relevant to STEPS objectives and will be targeted whenever possible.
The mobile ballooning facility will be guided by the nowcaster into position in coordination with other observational facilities. Information will be exchanged between the nowcaster and the communicator for the mobile electrical sounding crew by talking over radio, cell phone, and satellite phone links, as needed. Communication among crew members in the field will use short-range vehicle-to-vehicle or person-to-person radio links. Though guidance and coordination will be provided by the STEPS operations center, the final decision to launch a balloon will be made by the mobile electrical sounding crew chief in the field, because he will be best able to evaluate local safety issues and the likelihood of a successful flight.
Data acquisition by aircraft will be carried out only during daylight, but acquisition of electric field, lightning, and radar data can continue into the night, if the operations center monitors and communicates severe weather potential.
4.3.3.
NSSL/OU mobile mesonet vehicles
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Four-six mobile mesonet vehicles from the NSSL-OU Joint Mobile Research Facility, under the joint-direction of Erik Rasmussen (CIMMS) and Jerry Straka (OU) will take observations of wind, temperature, and moisture under and near targeted storms. These mobile units will also provide reports on whether targeted storms "appear" to be LP, MP, or HP. Photographic and video documentation will also be done as well as qualitative assessment of precipitation amounts and types, especially hail and its size.
The main scientific objectives for the operations of the mobile mesonets are organized into seven categories and detailed in the above linked document.
Rear-flank downdraft dynamics - Mobile mesonet observations will be taken in the region of the RFD to characterize this region of storm outflow, and the factors which determine its buoyancy and/or potential buoyancy near the ground.
Characterizing and documenting supercell precipitation - It will be the goal of the mobile mesonet teams to characterize surface precipitation and resultant cold pool production. To accomplish this, each team leader in each vehicle will record comments frequently about the intensity and character of the precipitation, especially when it changes. Further, each team will be equipped to make quick measurements of hailstone size and diameter, and will be required to gather specimens in ice chests for later study. These surface observations will be used to help verify microphysical inferences from the polarimetric measurements
Photographic documentation of the supercells will also be obtained for comparison to radar data. Photogrammetric cloud mapping will be performed using these photographs in order to compare the locations and dimensions of cloud features superimposed with radar data. These efforts will enable us to gain some knowledge relating the "appearance" of supercells to their actual precipitation distributions.
Lower boundary condition for wind synthesis - Analyses of VORTEX datasets has demonstrated that mobile mesonet observations can be used to greatly improve the wind synthesis from Doppler radar in the volume adjacent to the ground that is poorly sampled, if at all. The mobile mesonet strategy will be to sample regions of large gradients as thoroughly as possible, and homogeneous regions more sparsely. If a mobile mesonet team encounters a windshift or large changes in the state variables, they will sample these gradients carefully.
Forward-flank baroclinity - Observations will be made to characterize the nature of forward-flank precipitation character and intensity.
Lightning documentation - The mobile mesonet will record lightning observations to provide a degree of ground truth to lightning detection network strike data, as well as the lightning mapper. Mobile mesonet team leaders are encouraged to record information about CG strike location in the real-time digital audio stream.
Precipitation and cold pool documentation in non-supercell storms - In non-supercell storms, the mobile mesonets will be deployed per the directions of the nowcaster to obtain data about precipitation type, intensity, and surface state in support of the research activities of other STEPS PI's.
Boundary studies - On some days on which convection is not expected but mesoscale boundaries are within roughly 200 km of Goodland, 4-6 mobile mesonet teams will be dispatched to make observations of boundaries. This activity will be under the direction of Mr. Al Pietrycha of Texas Tech University.
4.3.4.
CSU storm chase van
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One instrumented storm chase van from CSU will be used to obtain time-resolved hail and rain measurements. The van is equipped with a hail collection net on top and a Young capacitance raingage. It will accompany the NSSL/OU mobile unit that will be attempting to target some of the storm cores. Since the CSU chase van is equipped with GPS, we will be able to have its positional information at the Ops Center for overlaying on the radar data. When the van is in a prime location where a radar cell with more than 50 dBZ is expected to pass over it, we will concentrate the RHI scans from the normal PPI/RHI sequence of scans on the cell and follow it as it passes over the van. The mobile coordinator and/or NSSL/OU team leader will help in steering the chase van away from any imminent danger such as might be expected from large hail.
4.4.
SDSMT T-28
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The SDSMT armored T-28 will provide in situ observations of hydrometeors, vertical winds, and electric fields from cloud base levels (~14 kft MSL) to mid-levels (21 kft MSL) of targeted storms. It can penetrate storms in regions where radar reflectivity is less than 55 dBZ at or above the aircraft altitude. It typically spends roughly one hour on-station. The T-28 is equipped to measure the complete spectrum of water and ice particles in clouds, ranging from cloud droplets a few micrometers in diameter to about 5-cm diameter hail. Shadow images are obtained for particles with diameter > ~25 micrometers using a suite of 3 imaging probes with varying sample volume and image resolution. Particle charge can be determined for a sample of imaged particles larger than ~0.2 mm. The local electric field vector is derived from measurements obtained with a suite of 6 electric field meters.
Storm penetration strategies: Since the T-28 can sample only very small portions of large storms, it is important that its operations are focused on storms which are also well-covered by radar and lightning mapping systems, and which are also the focus of the balloon-borne electric field soundings and mobile mesonet observations. The strategy for the T-28, with its relatively short mission time, will be to launch when a storm is blossoming through its earliest towering cumulus stages. It may be that the cloud development that triggers the T-28 launch decision will not produce the storm that is eventually sampled, but that the storm that will be studied will develop soon after this towering cumulus cloud development.
The focus of T-28 operations will be on penetrations of younger flanking cells, and the main storm updrafts and hail shafts in targeted storms. The interest in flanking cells is in monitoring the growth of potential hail embryoes and in early electrification associated with this growth. These observations will be important for the goals of understanding precipitation and hail development, and early electrification and charge transport, in developing severe storms. Flanking cells will often be difficult to detect on the CSU-CHILL radar. We will rely on the pilot to steer visually for the most active-looking portions of flanking cells.
Storms are quite variable in structure, and it is difficult to specify in advance a rigid procedure for obtaining suitable observations within the cores of large High Plains thunderstorms using the armored aircraft. Penetrations (schematic) of large mature storms will be directed along the lower tropospheric shear vector, which is typically the axis along which the storm organizes. (Probably such a storm will never appear during STEPS!) In this case the initial penetration would be from SW to NE along the storm axis.. If flanking cells are reaching the aircraft altitude, the pilot will be directed to penetrate them as he approaches the storm. The aircraft will then be sent northeastward through the storm on the inflow side of the main updraft and precipitation regions, as noted on the CSU-CHILL radar. Once further NE and clear of precipitation in a region where the electric field has reverted to its fair weather state, the aircraft will be directed to reverse course along a reciprocal heading and return through the storm and out through the flanking cells (if present).
For storms with different organization, variants on this penetration strategy will be employed with the overall goal being to sample the regions critical for precipitation development and transport, and electrification.
The Ops Center Team will have as their highest priority coordinated aircraft and balloon operations so that the different platforms are penetrating nearly the same regions at nearly the same time, the aircraft horizontally and the balloons vertically. As the aircraft can maneuver more readily than the balloon crews on the ground, it is likely that coordinated observing missions will be focused on the storms which the ground vehicles can intercept. It is desirable to stay with one storm through as much of its life cycle as possible, rather than jump to a new storm from a storm that has reached its peak intensity and started to decay.
4.5.
Satellite data archive at
CSU CIRA
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On days when operations are anticipated, the Ops Director will call John Weaver or Bard Zajac at the Cooperative Institute for Research in the Atmosphere (CIRA) to initiate NESDIS/CIRA archival of satellite imagery for the day. John can be reached at 970-491-8342, Bard at 970-491-8562. If neither can be reached just let the phone transfer to the Administrative Assistant who will pass the message on to John or Bard. Archival will be done in an easily accessible format, and these data will be available to all participants in the project.
The Ops Director will contact the Goodland WFO to request Rapid Scan Operations for GOES-8. This will allow for eight images per hour instead of the usual four. Goodland will need to know the start and end times for RSO. Start time will typically be two to three hours before convection is expected to form. End time should be specified as the time when the activity is predicted to be clear of the area. The Ops Director will remind the WFO contact to request that the SDM override the evening southern hemispheric wind sequence.
During the project, quick-look satellite loops of significant days will be placed on the CIRA web site. This site can be reached at the CSU website CIRA/RAMM RAMSDIS On-line. After the project is over, digital data (probably in McIDAS format) will be made available to participants via the CIRA Virtual Laboratory at the same web site.
4.6.
Yucca Ridge Field Station
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Yucca Ridge will be staffed on a 24x7 basis starting 22 May and will operate whenever convection is expected. We will have a live NLDN satellite feed and can provide telephone/e-mail summaries of lightning patterns to those in the field upon request. Our e-mail address: walyons@frii.com; Web site: FMA-Research.com; 970-568-7664 (voice); 970-690-0422 (PCS); 970-482-8627 (fax).
Located 200-400 km west northwest of the STEPS domain, Yucca Ridge is ideally suited for optical observations of TLEs (sprites/elves/blue jets). Yucca Ridge is situated on high terrain 20 km northeast of Fort Collins, CO (40 deg 40 min 06.2 sec N; 104 deg 56 min 23.4 sec W). The unobstructed horizon from the YRFS observing platform permits video imaging many exposed CG channels to ranges of 200 km or more (viewing should be especially good for LP supercells). IC flashes can be detected to ranges of 400 km using a combination of low-light and conventional CCD video systems. Continuous time lapse video of convective cloud systems in the STEPS domain will be made day and night (some moonlight required) to document storm morphology. When storms are present in the STEPS domain there is frequently strong subsidence west to the Front Range, permitting ideal viewing.
Yucca Ridge operations will be conducted in parallel with the main experiment. Our ideal scenario is for orogenic convection and/or supercells to form along the Front Range in mid-afternoon and evolve upscale into an MCS as the sprite-producing stratiform region passes through the STEPS domain just after sunset. Supercells in the STEPS domain after sunset will also be of great interest as we believe these do NOT produce sprites (though maybe blue jets!). The key measurements for the TLE phase of the experiment involve the LMA, electric field mills and fast electric field change measurements of New Mexico Tech, which will operate on a more or less continuous basis.
Our specific operational tasks will entail:
5. WEEKLY REVIEWS, GENERAL MEETINGS, and SEMINARS
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Reviews of operations, general meetings, and seminars will be open to all STEPS participants and other interested parties. The reviews will include a general review of recent operations, as well as discussion of observational priorities for the coming several days. These reviews are intended also to help identify which scientific goals are (are not) being met. These meetings will likely be held at the National Guard facility next to the Goodland NWS office or at Butterfly Aviation at the Goodland airport. The date, time, and location of these additional meetings will be announced at the regular morning briefings since no specific schedule can be determined ahead of time. Late mornings following the regular briefing or some time in the early afternoon will likely be the best times so as not to interfer with operations and give participants time to travel to Goodland from remote sites.
6. DATA MANAGEMENT
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There are several kinds of data that will be generated during the course of the field study. This include logs, notes, summaries, transcripts, data inventories, quick-look archives, and eventually the final dataset archives.
Jay Miller and Sherrie Fredrick, both of NCAR/MMM, will develop a detailed strategy and website whose main purpose will be to facilitate access to datasets archived by ATD, CSU, and the SDSM&T for instruments covered by the NSF facilities deployment pool. These institutions will be responsible for their own data processing, quality control, and archiving as outlined in their respective feasibility reports to the OFAP. Datasets from STEPS instruments not covered by the NSF facilities deployment pool will be handled in a similar way, with the parent institution again having the primary responsibility for data archiving.
The MMM website for STEPS data will also include either actual archives of or links to other ancillary datasets such as "quick-look products" generated during field operations, and other routine NWS surface, profiler, and upper air observations. MMM will rely heavily on existing archives such as those done routinely within UCAR/NCAR by SCD, UNIDATA, COMET, and RAP and by the various institutions responsible for deployment of the instruments involved in field measurements during STEPS. Besides Goodland (KGLD) the other NWS WSR-88D radars in order of decreasing relevance to STEPS are: Cheyenne WY (CYS), North Platte NE (KLNX), Dodge City KS (KDDC), Denver CO (KFTG), Hastings NE (KUEX) and Pueblo CO (KPUX).
6.1. Logs, notes, and summaries
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Logs of important events in which they were involved will be kept by the various coordinators in the Ops Center, including the operations director or his/her designee, the radar coordinator, the aircraft coordinator, and the storm intercept coordinator. In addition, individual facilities and mobile storm intercept units will also maintain logs of significant activities involving their facilities. Copies of these logs will be forwarded to a designated STEPS archivist in a timely manner.
A participant at each briefing and debriefing will be assigned to take notes during that session, and forward them in a timely manner (at least weekly?) to the STEPS archivist.
Where possible, these notes and summaries will be transmitted in a machine-readable format to facilitate organization of a comprehensive operational summary (posted at the project web site?) as the project progresses.
FMA will prepare (1) a running tally sheet of the number of TLEs observed during STEPS, (2) a summary sheet for daily TLE-related operations and (3) for all TLE observations days, a summary of operations at Yucca Ridge, including those of the cooperating research teams onsite and at remote locations.
6.2. Data inventories
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FMA will compile a listing of the following data resources for use by interested investigators: Daily video log times for clouds, lightning statistics, and preliminary TLE times,
As in past years, FMA can serve as a focal point for ordering NLDN reprocessed lightning stroke data. These are available on CD about two months after the end of the experiment. By compiling all requests into a single order, Global Atmospherics can provide a significant discount to STEPS researchers.
6.3. Quick-look archives
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Within 24 hours of each TLE-producing storm, a summary of initial findings and a rough log of sprite/elve times will be posted to the FMA web site (as in past years).
6.4. Data archives
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NCAR/MMM will make arrangements for acquiring the Goodland WSR-88D Level II data from either the NWS or from NCDC. Level II data covering the field season will be archived at NCAR/MMM. MMM already has several programs for reading the Level II data, and will provide these at no cost to the STEPS program.
7. DATA ANALYSIS PLAN
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Jay Miller:
I'm not sure if we want to make a first cut at who will be doing what as
far as the post-field campaign data analysis. I'm inclined to have some-
thing here to help us identify the various levels of analysis that might
be involved. For example, radar reflectivity maps are a reasonable
routine product that can be produced, but Doppler-derived winds are much
less routine.
Data analysis will be to a large-degree a collaborative effort among participating STEPS investigators. The overall analysis goal is to use the synthesis of observations and models to evaluate the role various precipitation development and transport mechanisms, and electrification processes, may or may not play in the microphysical and electrical evolution of High Plains thunderstorms.
7.1. Aircraft component
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Researchers involved in the analysis of data obtained from the aircraft platform will focus on analysis of the airborne microphysical and electric field data, in collaboration with these other investigators. They will collaborate with researchers preparing single- and multiple-Doppler and multiparameter radar data analyses, with lightning mapping researchers, with the balloon-borne electric field workers, and with those doing storm electrical modelling, to aid in the synthesis of the observations.
Priority days will be established from which observations are of greatest interest to one or more groups of investigators. Each group will then work on their data from these priority days to make it available to the rest of the community.
For analysis of airborne microphysical data, software has been developed that allows detailed analysis of the cloud liquid water and precipitation image data, as well as electric fields. Software to analyse precipitation particle charge is under development. A package also is available that ingests precipitation particle image data and automatically computes precipitation particle collision rates and particle surface temperatures, as a function of particle size, ambient temperature, and ambient cloud liquid water concentration. This latter package will be useful for evaluating the sign and magnitude of non-inductive ice-ice collision charge separation.
As the aircraft cannot sample a significant volume of any one storm for its entire cycle, the aircraft data will be augmented by other data and with modelling in order to arrive at an understanding of storm processes. The aircraft data will be used to help tune microphysical retrievals from the multiparameter radars. Aircraft, lightning, radar, and other data can further be used to initialize detailed cloud models including storm electrification and lightning processes. The results of these models can then be compared to the observations.
7.2. Mobile electrical soundings
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Logs of data collected will be provided to the STEPS archivist within a few days of each operation during STEPS, to provide the scientific community a first look at the data. Within four months of the end of STEPS operations, a summary of available soundings will be produced. The following information will be provided in the summary for each flight: the time, date, and location of launch; the end time, end date, and maximum height of the flight; the maximum electric field measured during the flight; and a brief description of data quality. Data from the modified dropsondes will also be provided at this time for all flights in a standard format for environmental soundings. Once STEPS investigators have prioritized storms for analysis, electric field data from all available soundings for the 2-3 storms with the highest priority will be processed within four months. Electric field soundings from the remaining cases will be processed by the end of the following summer. The processed data provided for each flight will consist of the electric field, pressure, temperature, dew point, horizontal wind speed and direction, ascent rate, time, latitude, longitude, and altitude at approximately 1-s intervals along the balloon track.
APPENDICES:
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A. Voice communications
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Voice communication by satellite phone, cellular phone, and radio will be used to contact the Operations Center for weather updates and guidance concerning target storms. A cellular phone will be supplemented by a satellite phone, because cellular phone coverage is poor in much of the region planned for STEPS operations. Three dial-up phone lines (719 346-6037, 346-6038, and 346-6039) are connected into the Ops Center. The last number (719-346-6039) has a FAX hookup that will intercept the call after six rings and assume it is a FAX coming in.
One dial-up phone line (970 354-7846) is connected into the S-Pol radar van.
Proper voice communications over radio should be used. Generally, all traffic should be brief and to the point. Always listen first before transmitting since someone else may be using the frequency. If you must break in, especially for an emergency, wait for the first OVER or time when no one is transmitting, and immediately transmit something like: BREAK, BREAK, OPS this is MOBILE ONE, OVER. When you hear something like this, it is absolutely essential that you be quiet if you are not OPS or MOBILE ONE and allow OPS to establish communication with MOBILE ONE. It is also very important to remain calm, especially when important messages concerning severe weather and safety are involved. Such instances will likely also occur when radio communications are at their worst.
Clear communication should be established before proceeding with any message. To ensure understandable messages, each person should speak clearly and slowly, avoid contractions, and transmit only short parts before pausing to receive a reply. Most numbers, especially multiple digit ones, are usually difficult to understand over radios so they should be spelled out. For example: one, two, three, four, five, ..., one-niner, two-eight-five, ... If you send a number like 15 as fifteen rather than one-five, you significantly reduce the chances that the number will be understood.
Since some words can be difficult to understand, they may need to be spelled out using any phonetic alphabet that you are familiar with. For example, one such possibility is: ALPHA, BAKER, CHARLIE, DELTA, ECHO, FOXTROT, GOLF, HOTEL, INDIA, JULIET, KILO, LIMA, MIKE, NOVEMBER, OSCAR, PAPA, QUEBEC (keybec), ROMEO, SIERRA, TANGO, UNIFORM, VICTOR, WHISKEY, XRAY, YANKEE, ZULU. It is important when using any phonetic alphabet that the word you use to spell out other words is itself easily understood.
| ACTION | MESSAGE |
|---|---|
| OPS calling SPOL | SPOL this is OPS. OVER. |
| SPOL responding | This is SPOL. OVER. |
| OPS sending message | This is OPS. Request that you move your scan sector clockwise one-five degrees. OVER. |
| SPOL acknowledging message | This is SPOL, understood, move scan one-five degrees clockwise. OUT. |
| OVER - means you are through transmitting, but expect a reply. OUT - means you are through transmitting and expect NO reply. ROGER - means you understand a message, usually followed by OUT. |
|
B. Radio frequencies
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C. Data formats
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C.1. Radars
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There are three possible formats for radar data: (1) Universal, (2) DORADE, and (3) Level II.
C.2. Lightning mapping system
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C.3. Environmental soundings
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C.4. Storm electrical soundings
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Jay Miller:
This will include links and such from Goodland WFO. Most everything
will have been done by the start of the field program. Administrative
will include mostly issues about logs, notes, etc generated in the
field. Who/where etc will these be archived.
D. Local logistics and Administrative support
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SDSMT plans to establish an office with a couple of phone lines at the airport. We will be glad to serve as a location from which folks temporarily at the airport can make phone calls, leave small equipment or briefcases, etc. We have no plans at the moment to have a copier, fax machine, or internet access at that office. Larger equipment in some cases may be temporarily stashed in the hangar, if we are given some advance warning so we can try to find the space and negotiate with the FBO. We may try to set up a VHF scanner at the office.
E. Safety
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All field personnel should know what actions to take to protect themselves against severe weather. Some relevant material from the NWS Office of Meteorology is available at their severe weather awareness website.
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