Director's Message |
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Overview |
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| The Mesoscale and Microscale Meteorology (MMM) Division is one
of nine programs or divisions within the National Center for Atmospheric Research (NCAR).
The mission of MMM is one of basic research to advance the fundamental understanding of
mesoscale and microscale processes and to improve the modeling, observation, and
prediction of these processes. The Division's research ranges from basic to applied.
However, for the direct transfer of knowledge to benefit society, we rely on collaborative
efforts with other NCAR divisions and programs and University Corporation for Atmospheric
(UCAR) programs whose missions are more directly aligned to technology transfer. Much of
our research also involves collaborations with scientists outside the division, especially
scientists at universities. The division is organized into six science groups, a computing system management group, and administrative services. It consists of 72 staff with 28 scientists, including 15 senior scientists and one senior scientist emeritus, and 10 project scientists. Fifteen scientists/project scientists hold joint appointments with other NCAR divisions. Collocated with the division is a group of three scientists from the National Oceanic and Atmospheric Administration (NOAA) National Severe Storms Laboratory (NSSL) who specialize in airborne dual-Doppler observations of mesoscale systems. This group augments the MMM program in mesoscale observations. An external advisory committee assists the division in determining its scientific direction. The committee is currently comprised of four university colleagues and two scientists from ATD and CGD. It met for the first time in a division science planning retreat held in November 1997. In addition to the science group structure, in FY 98 we began discussions on organizing the division along programmatic themes. These themes were identified through a yearlong strategic planning process in which the external advisory committee played a major role in the early definition of these themes. In addition to the two primary programs, sub-components associated with each program and four smaller research programs were identified. Each program and sub-component have goals toward which the research efforts are directed. The programs and their goals are described in detail in the MMM Scientific Strategic Plan. The Annual Scientific Report (ASR) provides a comprehensive summary of research accomplishments and activities carried out in FY 98 primarily along the science themes of our Strategic Plan. In the section that follows I will briefly describe how we expect our research to evolve over the next two years as we work toward the broader goals of the Strategic Plan. |
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Scientific Goals and Plans |
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| The purpose of the two primary programs is to facilitate
communications between researchers within the division, in other NCAR divisions, and with
scientists outside NCAR working on common programs. Through this communication process the
programs will identify areas where collaboration and coordination of efforts will help
achieve the goals of the program and will facilitate the process for seeking funding for
the program either from NSF or from other external sources. With the program structure
within the division, a primary purpose of the science groups is to allow scientists within
the division the opportunity to easily move between the various programs as opportunities
and interests change. The division's Strategic Plan referred to above defines two primary programs within the division and their goals. These programs are of the highest priority for the division. They are the Prediction of Precipitating Weather Systems Program, designed to advance the understanding and prediction of significant precipitation events in order to reduce forecast errors toward the limits of predictability, and the Mesoscale and Microscale Processes and Impacts Program, designed to quantify the large scale effects of mesoscale and microscale processes and to develop physically based methods to account for these effects in large-scale models. The latter program addresses the parameterization problem in both climate simulation and prediction and in weather forecasting models. In addition, the division supports activities defined by individual scientists that may not be directly related to the major programs. Our goal here is to provide research opportunities that could become the impetus for moving forward in new, unexpected directions leading to possible future emphases or changes in the focus of the major scientific goals. Within this portion of the program we have identified four smaller research programs that are emphasized for their uniqueness, for the fact that they represent scientific research that is expanding at the national/international level, or because they complement larger programs elsewhere within NCAR. They are (1) Ice Microphysics Research, (2) Wildfire Research, (3) Geophysical Turbulence Research, and (4) Chemistry, Aerosols, and Dynamics Interactions Research. Goals for these smaller programs are also provided in the division's Scientific Strategic Plan. |
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Plans for the Next Two Years for the Major Programs |
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Research Plans for the Prediction of Precipitating Weather Systems Program |
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| Over the next two years the Prediction of Precipitating Weather Systems Program will be tightly coupled to U. S. Weather Research Program (USWRP) research initiatives, with particular emphasis on improving the quantitative prediction of precipitation (QPF). Following the priorities identified in the Strategic Plan, the division will emphasize research on the predictability and lifecycle of mesoscale precipitation systems, the physical processes within these systems, the assimilation of mesoscale observations, and advanced numerical weather prediction. Projects in these areas are highly inter-related, and research will be integrated to achieve synergy in the broader program. | |||
Mesoscale Predictability |
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| Precipitation embedded within synoptic-scale flow is typically concentrated in cells or bands with scales below 100 km, and little is known about predictability at these scales. To address this topic, a numerical model with adaptive grid capability will be used to simulate a finite-amplitude baroclinic wave and resolve explicitly the processes responsible for organizing the smaller scale precipitation. Numerical experiments will be designed to determine the predictability at scales controlling precipitation, the time scale for error growth in those scales to contaminate larger scales, and the effect of uncertainty in the larger scale on the predictablity of smaller scales. | |||
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Life Cycle of Precipitating Weather Systems |
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| Research to identify the factors that control the evolution of
heavy precipitation systems will be conducted through diagnostic studies of selected
precipitation systems and statistical analysis of a dynamically based mesoscale
climatology for these systems. Both observational analyzes and numerical simulations will
be utilized to analyze the life cycle of mesoscale convective systems, with particular
emphasis on factors that regulate the initiation of convection, the dissipation of
organized convection, and the regeneration of subsequent convection. Knowledge gained will
facilitate the improved representation of convection in numerical weather prediction
models and the advancement of non-dynamical nowcasting techniques. Although cloud microphysics play an important role in convective dynamics and precipitation physics (and hence in QPF), existing microphysical parameterizations are known to possess significant deficiencies. Using detailed microphysical information from polarization radar measurements along with improved aircraft in situ observations, the accuracy of bulk microphysical schemes will be evaluated and improved physically based parameterizations will be developed. This research will require the improvement of radar-based particle classification schemes through comparison with aircraft in situ observations and simulation of comprehensively observed precipitation systems to enable a detailed evaluation of the simulated precipitation type, distribution, and fall speed. Local variations in land-surface characteristics, such as vegetation and soil moisture, have critical influences on the planetary boundary layer which in turn affect the timing, location, and duration of precipitation events. This variability will be addressed, seeking to better understand and quantify important surface influences to improve QPF during the warm convective season and to enhance the coupled surface-atmosphere modeling of snow accumulation, melting, and runoff. |
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Mesoscale Data Assimilation |
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| The use of non-traditional observations (radar, satellite,
ACARS, GPS, etc.) in initializing high resolution of short-range prediction models offers
great potential for improving the accuracy of QPF. Integrated research in a number of
areas will be required to develop the necessary knowledge and tools for optimal use of
these observations in both cloud and regional scale numerical weather prediction (NWP)
models. To this end, development of a community mesoscale data assimilation system based
on MM5 and its full physics adjoint will continue, and user support for community use will
be strengthened. As the Weather Research and Forecast (WRF) model matures development of
the data assimilation system will transfer to this new model. Techniques will be explored to assimilate radar observations of convective storms into cloud-scale prediction models and the impacts of the more detailed data available from polarmetric radar will be assessed. Assimilation of remotely sensed observations, with emphasis on moisture variables (ground-based global positioning system (GPS), rainfall rate, satellite-based precipitable water, water vapor winds, etc.), will continue with the development of required forward operators, estimation of error statistics, and evaluation of potential improvements in the short-range prediction of mesoscale precipitation systems. Advanced assimilation techniques will be explored, with the goal of relaxing assumptions in current schemes of normality of statistics, stationary and isotropic background covariances, perfect models, and various linearizations (particularly of moist physics). Initial work will focus on the development of a time varying background error covariance matrix based on the statistical results from a mesoscale ensemble. |
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Joint Operational/Research Community Model |
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| The WRF model project will continue the joint development
(with the operational community) of an advanced mesoscale forecast model and assimilation
system to improve the understanding and prediction of important mesoscale precipitation
systems. Over the next two years, emphasis will focus on developing a research quality
modeling system that will be distributed as a community model to promote university
involvement in further development and evaluation of the model. To this end, alternative
prototypes for the model numerics will be evaluated, the design of the overall model
architecture together with the dynamical model solver will be finalized, and the model
code will be constructed following a strict set of standards. The best existing physics
packages will be adapted to the dynamical model and new approaches will be explored for
treating physics in high-resolution (non-hydrostatic) applications. To initiate model evaluation for real-data NWP forecasts, flexible procedures will be designed for initializing the model from a variety of analysis products. Development of the data assimilation system will also begin, with focus on construction of the adjoint and tangent linear models and design of 3DAVAR and 4DVAR assimilation strategies. Incorporation of non-traditional observational data will be crucial in seeking to improve the fine scale forecast accuracy. |
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Research Plans for the Mesoscale and Microscale Processes and Impacts Program |
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| Throughout the next two years, research will focus on
activities addressing the primary goal of the Mesoscale and Microscale Processes and
Impacts Program, as stated in the division's Strategic Plan. The approach calls on a
combination of basic research, including fine-scale numerical simulations of cloud systems
forced by objectively analyzed field data, idealized simulations, and field experiment
analysis, leading to methods for parameterization of mesoscale and microscale systems. A
key aspect of this work is that the focus will be on the full interaction or coupling of
microphysics, turbulence, radiation, and surface processes through cloud system
dynamics. It is an important contribution to the NCAR Clouds in Climate Program
(CCP). Selected activities will draw on a heritage of convection and boundary layer research in MMM including oceanic cloud systems, boundary-layer processes and cloud systems over land, convectively generated cirrus, and parameterizations in climate system models. A common scientific theme will be to derive new approaches to parameterization in circumstances where no clear scale-separation exists, a fundamental issue related to organized structures. We will also evaluate the effects of detailed three-dimensional radiative transfer on the energy budget and evolution of cloud-resolving models. |
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Oceanic Cloud Systems |
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| Studies of GATE and TOGA COARE cloud systems will continue
using a combination of modeling and observations. New work will stress issues in scale
interaction, such as explicit ocean-atmosphere coupling, the role of organized convection
and cloud-radiation feedback, and sensitivity to microphysical and turbulence
parameterizations. Also, the three-dimensional simulations will need to be fully evaluated
against the observational data sets. Cloud system simulations and idealized dynamical modeling in support of TRMM Kwajalein will be pursued. A key objective is to connect the microphysical process studies, which have so far been the focus of TRMM modeling, to the big picture of the global water cycle. The augmentation of traditional data sets by space-borne observations is necessary to fully evaluate cloud system realizations and will have a growing emphasis in the division. The use of cloud-resolving simulations of Hadley/Walker circulations in domains spanning many thousands of kilometers will seek to increase our knowledge of key aspects of intra-seasonal variability in the tropics. Studies will include the simulations of the ITCZ/trade-wind cumulus complex, the role of cloud radiative interaction, and quantification of the sophistication required of microphysical parameterizations. The new massively parallel non-hydrostatic global code (EULUS) will be used for idealized global impact studies. The role of organized convection in westerly wind bursts and in the Asia-Australia summer monsoon will be investigated. A new non-hydrostatic code, which has the option of either resolving convection or (on a suitably large computational grid) parameterizing convection, will be used to examine the resolution dependence of convection parameterizations, especially when scale separation is an inappropriate assumption. High-resolution weather forecasting models will be analyzed to determine how organized convection is treated in monsoon circulations. The structure and transport properties of convection in sub-polar airflow (cold-air outbreaks) behind mid-latitude cyclones will continue. After completion of ongoing work on open-cellular organization, other regimes of organization will be investigated. The ultimate goal is to concurrently simulate the entire range of organized convection regimes spanning the ocean-scale region from the edge of the ice sheet to the cold front, although it is not computationally feasible at present. Large-eddy simulation studies of marine stratocumulus will continue. In addition to studies of cloud-top entrainment, the roles of mesoscale organization, of drizzle formation, and the effects of short-wave radiation will be addressed. Also to be investigated are complex boundary layer structures. |
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Boundary-Layer Processes and Cloud Systems Over Land |
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| Emphasis will be on modeling and observational approaches in
order to meet the long-term goals of quantifying the interactions between the planetary
boundary layer and the underlying surface and improving their treatment in large-scale
models. A new study of precipitating convective cloud systems over land will begin. First, we will participate in TRMM-Brazil studies and the Large-scale Biosphere-Atmosphere (LBA) experiment of GEWEX, in order to examine the diurnal cycle of convection and the role of convective organization in atmospheric heating. Second, we will conduct cloud-resolving studies of convection from data collected during the DOE/ARM Intensive Observation Period (mid-June to mid-July 1997) conducted in the Oklahoma-Kansas locale. The diurnal variability of the planetary boundary layer and its interaction with the underlying surface is integral to this effort. A combination of observations, simulation and dynamical modeling during MCTEX began to quantify how sea-breeze circulations affect convection initiation. This aspect, together with several other aspects of mesoscale organization, will be examined in a new field program in the Darwin area being planned as a collaborative effort by members of the tropospheric dynamics, atmospheric chemistry, and middle-atmosphere dynamics communities. |
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Convectively Generated Tropical Cirrus |
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| Convectively generated cirrus is a major uncertainty affecting cloud-radiation interaction in the tropics. While dynamical aspects control the overall organization of the parent-closed system, the factors that control the evolution and extent of the cirrus canopy are poorly understood. A cross cutting initiative will be planned that will draw on resident expertise in dynamics, radiation, and microphysics and may stimulate a community effort. | |||
Parameterization |
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| Parameterization of sub-grid scale processes is a well-recognized problem in large-scale modeling and prediction. Ongoing work on methods to parameterize marine stratocumulus will continue. In the next two years, new work will center on precipitating convective cloud systems to examine parameterization of those systems in the CSM/CCM3. The synthetic results from cloud-resolving models, validated using observational data sets, will be used in conjunction with single-column modeling. Selected issues are sub-GCM-grid scale cloud radiative interaction, evaluation and improvement of convective parameterization, and incorporation of a new convective momentum flux parameterization scheme for organized convection and the analysis of its impact on the general circulation. | |||
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Three-dimensional perspectives of the total condensate mixing ratio of 0.01 g kg-1. (a) (left) Nonsquall clusters at 1800 UTC on 2 September viewed from above the
southeast corner. (Click here to view a larger version of the three figures.) |
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Plans for the Next Two Years for the Smaller Research Programs |
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Ice Microphysics Research |
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| This program is really a national level initiative MMM/NCAR is
helping to facilitate. We refer to the activity as ICE. The initiative will include a
number of planning meetings where the overall objectives of the initiative are defined by
the community. It is expected that these objectives will be outlined in a science plan
that would be available within a year. Scientists within the division as well as several
from various universities will take the lead in this planning process. As part of the initiative, attempts will be made to encourage students to enter into microphysical research. In this regard, planning is underway for a colloquium in the summer of 1999 on ice microphysics sponsored by ASP. A planned outcome of the colloquium will be a collection of the presentations from the speakers that will serve as a summary of the current state of knowledge of ice microphysics. This will be used as the basis for defining the overall ICE initiative. |
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Wildfire Research |
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| The two main aspects of the wildfire research are numerical
modeling and observations. The modeling work will consider applications of a fully
implemented version of the Missoula laboratory's BEHAVE and BURNUP codes which are
probably about the best and most flexible parameterizations of fire spread behavior
available. The modeling studies will consider small enough scales to focus on the role of
vortex dynamics on fire behavior and their parametric behavior. These studies will include
both enhanced reconnection and hairpin vortices. Case studies in collaboration with groups
from Australia and North America will also be part of the modeling studies. Observational studies will continue between colleagues of NCAR, the U.S. Forest Service, the University of Colorado, and the Cooperative Research Center, Australia, with both airborne and tower-based observations. The tower or surface observations will concentrate on refining the previous single IR camera observations. Base lining of velocity estimations, using multi-camera observations to cover the full temperature range, and using multi-angles positions to better view the morphology of the fire winds will be considered. Observations of various radicals such as CH or C2 are being considered to better establish what it is the IR camera is viewing. Further airborne observations such as "frost fire" may be considered in the next fiscal year. Software development will be a critical aspect of all of these observational studies. |
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Geophysical Turbulence Research |
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| The Geophysical Turbulence Program is in the formative stages and is not fully defined. However, we expect that the main emphasis will be on clear air turbulence with emphasis on turbulence generated at jet-stream levels and by flow interactions with topography. Work will include very high-resolution simulations of turbulent events including further work on two events over the Front Range of the Rocky Mountains that may have contributed to recent aircraft accidents. In addition, we plan high-resolution simulations of cases over the North Pacific where high-resolution dropsonde data were taken during NORPEX 98 and NORPEX 99. | |||
Chemistry, Aerosols, and Dynamics Interactions Research |
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| We expect that the Chemistry, Aerosols, and Dynamics
Interactions Research Program will be coupled to the larger NCAR Global Tropospheric
Chemistry Program (GTCP) and will involve strong interactions with ACD in a number of
areas. These include joint planning of and the participation in a major field campaign in
Darwin, Australia, about 2001. Meteorological objectives of this program will include
excitation of gravity waves by deep convection and their propagation into the
stratosphere, and the initiation and evolution of the convection and its impacts on the
larger scales. The chemistry objectives will focus on chemical processes within the clouds
and transport of various chemical species from the boundary layer to the high atmosphere. As the WRF model development proceeds, options will include predictions of chemistry. Scientists from ACD and MMM will collaborate in this development. It is expected that this effort will lead to a model that can be applied to chemistry transport problems on many scales including regional scales down to cloud scales. The main emphasis in chemistry research within MMM will be on the impact of clouds on the chemical processes occurring within the clouds and on the impact of chemical processes on the clouds. As part of this research will be efforts to understand the sources, sinks, and evolution of various aerosols and their impacts on clouds. |
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| Table of Contents | Director's Message |
| Significant Accomplishments | FY 98 Publications |
| Community and Educational Activities | Staff, Vistors & Collaborators |
