Events (Upcoming & Past)

Past MMM Events

High-resolution climate simulations using a regional climate model

Dominic MatteESCER/UQAMMontreal, Quebec, Canada

Although practitioners of dynamical downscaling are well aware that the jump of resolution between the driving data and the nested regional climate model impacts the simulated climate, the issue has never been properly studied. Larger is the jump of resolution, larger is the distance from the lateral inflow to fully develop the small-scale features permitted by the increased resolution. This latter point has repercussions on the computational cost, and becomes an issue for large jump of resolution.

My research has focused on those methodological issues for high-resolution climate simulation purposes. Using the idealized “perfect model” framework so-called the Big-Brother experiment, we have shown that the multiple nesting approach is not only appropriate for a large jump of resolution between the GCM and the RCM, but also reduces the computational cost. This is explained by a substantial reduction of the spatial spin-up, reducing, then, the minimal required domain size. Those results have led to a new study design to deepen our understanding about spatial spin-up. Using a similar Big-Brother experiment but with different jumps of resolution between the lateral boundary conditions and the grid mesh of the nested model, we have shown that the spatial spin-up is intimately linked to the jump of resolution and the weather regime. Thus, explaining the reduction of spatial spin-up observed in our previous study using the multiple nesting approach. In other world, since the multiple nesting reduces the jump of resolution, it also reduces the spatial spin-up distance. As a paramount result of our study, an empirical equation to estimate the spatial spin-up lateral distance has been developed. A complementary part of my research consists in an application of these findings for simulating the freezing and frozen precipitation occurrences in a climate-change context using various precipitation-type diagnostic algorithms.

In the last decade, several efforts have been made to foster high-resolution climate-change information through coordinated experiments such as CORDEX in which a strict simulation framework is imposed, including domain size and location. Ours findings have shed light on some of the methodological issues associated to dynamical downscaling which might help to elaborate such frameworks. 

Thursday, 9 February 2017, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory, 3450 Mitchell LaneBldg. 2, Main Auditorium, Room 1022

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, February 10, 2017 - 5:30am to 7:00am

High-resolution climate simulations using a regional climate model

Dominic Matte
ESCER/UQAM
Montreal, Quebec, Canada

Although practitioners of dynamical downscaling are well aware that the jump of resolution between the driving data and the nested regional climate model impacts the simulated climate, the issue has never been properly studied. Larger is the jump of resolution, larger is the distance from the lateral inflow to fully develop the small-scale features permitted by the increased resolution. This latter point has repercussions on the computational cost, and becomes an issue for large jump of resolution.

My research has focused on those methodological issues for high-resolution climate simulation purposes. Using the idealized “perfect model” framework so-called the Big-Brother experiment, we have shown that the multiple nesting approach is not only appropriate for a large jump of resolution between the GCM and the RCM, but also reduces the computational cost. This is explained by a substantial reduction of the spatial spin-up, reducing, then, the minimal required domain size. Those results have led to a new study design to deepen our understanding about spatial spin-up. Using a similar Big-Brother experiment but with different jumps of resolution between the lateral boundary conditions and the grid mesh of the nested model, we have shown that the spatial spin-up is intimately linked to the jump of resolution and the weather regime. Thus, explaining the reduction of spatial spin-up observed in our previous study using the multiple nesting approach. In other world, since the multiple nesting reduces the jump of resolution, it also reduces the spatial spin-up distance. As a paramount result of our study, an empirical equation to estimate the spatial spin-up lateral distance has been developed. A complementary part of my research consists in an application of these findings for simulating the freezing and frozen precipitation occurrences in a climate-change context using various precipitation-type diagnostic algorithms.

In the last decade, several efforts have been made to foster high-resolution climate-change information through coordinated experiments such as CORDEX in which a strict simulation framework is imposed, including domain size and location. Ours findings have shed light on some of the methodological issues associated to dynamical downscaling which might help to elaborate such frameworks. 

Thursday, 9 February 2017, 3:30 PM
Refreshments 3:15 PM
NCAR-Foothills Laboratory, 3450 Mitchell Lane
Bldg. 2, Main Auditorium, Room 1022

First Name: 
Caroline
Last Name: 
Haws
Phone Extension (4 digits): 
8189
Email: 
haws@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, February 9, 2017 - 3:30pm to 5:00pm

Cloud-Atmospheric Boundary Layer-Surface Interactions on the Greenland Ice Sheet

Amy SolomonUniversity of Colorado and NOAA/ESRLBoulder, Colorado

The fate of the Greenland Ice Sheet (GIS) in a warming world will impact climate globally. For example, if the entire GIS melts, sea level is predicted to rise by up to 7 meters, thereby increasing flooding of coastal land, causing saltwater intrusion into groundwater, and potentially impacting ocean circulations through increased freshwater fluxes. 

Over the past two decades there has been a trend towards increasing GIS melt and mass loss, leading to a number of record melt years and providing increasing contributions to sea-level rise. This presentation is focused on the recent extreme melt event of July 2012, where over 90% of the GIS surface experienced melt, even at Summit Station (hereafter Summit, 3216 meters above sea level), which previously experienced melt 126 years before in 1889. 

Surface energy balance models have been used to demonstrate that melt at the top of the GIS would not have occurred in July 2012 without the warming effect of low-level thin mixed-phase clouds. We present results of the impact of clouds at Summit from measurements taken during The Integrated Characterization of Energy, Clouds, Atmospheric State and Precipitation at Summit (ICECAPS) campaign. We then explore the July 2012 extreme melt event in detail with limited-area model simulations that allow us to go beyond cloud radiative effect estimates and to investigate the coupled feedbacks related to these low-level clouds that influence surface energy fluxes, and therefore the energy available for melt, at Summit and across the GIS.

Thursday, 19 January 2017, 3:30 PM

Refreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg. 2, Main Auditorium, Room 1022

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, January 20, 2017 - 5:30am to 7:00am

Cloud-Atmospheric Boundary Layer-Surface Interactions on the Greenland Ice Sheet

Amy Solomon
University of Colorado and NOAA/ESRL
Boulder, Colorado

The fate of the Greenland Ice Sheet (GIS) in a warming world will impact climate globally. For example, if the entire GIS melts, sea level is predicted to rise by up to 7 meters, thereby increasing flooding of coastal land, causing saltwater intrusion into groundwater, and potentially impacting ocean circulations through increased freshwater fluxes. 

Over the past two decades there has been a trend towards increasing GIS melt and mass loss, leading to a number of record melt years and providing increasing contributions to sea-level rise. This presentation is focused on the recent extreme melt event of July 2012, where over 90% of the GIS surface experienced melt, even at Summit Station (hereafter Summit, 3216 meters above sea level), which previously experienced melt 126 years before in 1889. 

Surface energy balance models have been used to demonstrate that melt at the top of the GIS would not have occurred in July 2012 without the warming effect of low-level thin mixed-phase clouds. We present results of the impact of clouds at Summit from measurements taken during The Integrated Characterization of Energy, Clouds, Atmospheric State and Precipitation at Summit (ICECAPS) campaign. We then explore the July 2012 extreme melt event in detail with limited-area model simulations that allow us to go beyond cloud radiative effect estimates and to investigate the coupled feedbacks related to these low-level clouds that influence surface energy fluxes, and therefore the energy available for melt, at Summit and across the GIS.

Thursday, 19 January 2017, 3:30 PM

Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg. 2, Main Auditorium, Room 1022

First Name: 
Caroline
Last Name: 
Haws
Phone Extension (4 digits): 
8189
Email: 
haws@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, January 19, 2017 - 3:30pm to 5:00pm

Sensitivity of simulated tropical-cyclone-like vortices over the western North Pacific and boundary layer clouds over the Southeast Pacific to the choice of cumulus parameterization scheme in WRF-ARW

Chunxi Zhang International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at MānoaHonolulu, HI 

 The simulated tropical-cyclone-like vortices (TCLVs) and tropical cyclones are very sensitive to the choice of cumulus parameterization (CP) schemes in the WRF-ARW model. The possible relationship between the TCLVs and environmental conditions unique to each CP scheme is explored. In particular, the link of the environmental conditions to convective self-aggregation is investigated. We used moisture–sorted analysis, especially the moisture-sorted streamfunction, to assess the processes and features that have been found in studies of self-aggregation and have been shown to be important in controlling self-aggregation.

Two versions of Tiedtke CP schemes have been implemented into the WRF-ARW model to improve the representation of marine boundary layer (MBL) over the southeast Pacific (SEP). The simulations with other CP schemes failed to reproduce the geographical distribution of cloud fraction and the observed cloud regime transition, and displayed an MBL too shallow compared to observations. The improved simulations with the Tiedtke schemes can be attributed to a more active parameterized shallow convection with the Tiedtke CP schemes than with the other CP schemes tested. This played a critical role in lifting the inversion base and the low cloud layer. Results from additional sensitivity experiments employing different planetary boundary layer (PBL) parameterization schemes demonstrated that the basic feature of the MBL structure and low clouds over the SEP were not particularly sensitive to the choice of the PBL scheme. However, the newly implemented E-ε PBL scheme can improve the geographical distribution of the cloud fraction over SEP.

Thursday, 12 January 2017, 3:30 PM

Refreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg. 2, Main Auditorium, Room 1022

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, January 13, 2017 - 5:30am to 7:00am

Sensitivity of simulated tropical-cyclone-like vortices over the western North Pacific and boundary layer clouds over the Southeast Pacific to the choice of cumulus parameterization scheme in WRF-ARW

Chunxi Zhang 
International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at Mānoa
Honolulu, HI 

 The simulated tropical-cyclone-like vortices (TCLVs) and tropical cyclones are very sensitive to the choice of cumulus parameterization (CP) schemes in the WRF-ARW model. The possible relationship between the TCLVs and environmental conditions unique to each CP scheme is explored. In particular, the link of the environmental conditions to convective self-aggregation is investigated. We used moisture–sorted analysis, especially the moisture-sorted streamfunction, to assess the processes and features that have been found in studies of self-aggregation and have been shown to be important in controlling self-aggregation.

Two versions of Tiedtke CP schemes have been implemented into the WRF-ARW model to improve the representation of marine boundary layer (MBL) over the southeast Pacific (SEP). The simulations with other CP schemes failed to reproduce the geographical distribution of cloud fraction and the observed cloud regime transition, and displayed an MBL too shallow compared to observations. The improved simulations with the Tiedtke schemes can be attributed to a more active parameterized shallow convection with the Tiedtke CP schemes than with the other CP schemes tested. This played a critical role in lifting the inversion base and the low cloud layer. Results from additional sensitivity experiments employing different planetary boundary layer (PBL) parameterization schemes demonstrated that the basic feature of the MBL structure and low clouds over the SEP were not particularly sensitive to the choice of the PBL scheme. However, the newly implemented E-ε PBL scheme can improve the geographical distribution of the cloud fraction over SEP.

Thursday, 12 January 2017, 3:30 PM

Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg. 2, Main Auditorium, Room 1022


First Name: 
Caroline
Last Name: 
Haws
Phone Extension (4 digits): 
8189
Email: 
haws@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, January 12, 2017 - 3:30pm to 5:00pm

What users’ decisions tell us about how we communicate hazard information

Kelsey Mulder University of ReadingReading, United Kingdom

Natural hazard modelling has greatly improved over the last decade, enabling us to better quantify the uncertainty in weather and climate forecasts. Communicating that uncertainty information to end-users is an important, yet difficult task. If done well, the additional information has the potential to help end-users make better-informed decisions. However, communicating this complicated information runs the risk of confusion to the end-user, leading to potentially dangerous decisions. This talk presents decision-based research that provides general advice for communicating uncertain information across hazards. Results from an intensive expert-based study on volcanic ash maps and a broader survey of experts and non-experts on presenting hazard information in graphs will be presented, including preliminary results from an eye-tracking study.

Thursday, 5 January 2017, 3:30 PM

Refreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell Lane

Bldg. 2, Main Auditorium, Room 1022

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, January 6, 2017 - 5:30am to 7:00am

What users’ decisions tell us about how we communicate hazard information

Kelsey Mulder 
University of Reading
Reading, United Kingdom

Natural hazard modelling has greatly improved over the last decade, enabling us to better quantify the uncertainty in weather and climate forecasts. Communicating that uncertainty information to end-users is an important, yet difficult task. If done well, the additional information has the potential to help end-users make better-informed decisions. However, communicating this complicated information runs the risk of confusion to the end-user, leading to potentially dangerous decisions. This talk presents decision-based research that provides general advice for communicating uncertain information across hazards. Results from an intensive expert-based study on volcanic ash maps and a broader survey of experts and non-experts on presenting hazard information in graphs will be presented, including preliminary results from an eye-tracking study.

Thursday, 5 January 2017, 3:30 PM

Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane

Bldg. 2, Main Auditorium, Room 1022

First Name: 
Caroline
Last Name: 
Haws
Phone Extension (4 digits): 
8189
Email: 
haws@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, January 5, 2017 - 3:30pm to 5:00pm

Adventures in probing tornadoes and their parent supercells with mobile, rapid-scan, Doppler radars

Howard (Howie “Cb”) BluesteinSchool of Meteorology, University of Oklahoma, NormanNorman, OK

Rapid-scan Doppler radar measurements of tornadoes and their parent supercells have allowed us to view aspects of tornadogenesis that would otherwise be impossible to document because they take place on time scales too short to measure with conventional radars. During the past decade we have been using a mobile, phased array, X-band Doppler radar from the Naval Postgraduate School and a mobile, mechanically scanning, polarimetric, X-band, Doppler radar from the University of Oklahoma to make measurements during annual spring field experiments in the Plains of the U. S. In this talk I will summarize what we have learned about the following aspects of tornado behavior: (1) the origin of tornadogenesis in supercells from the perspective of the Tornadic Vortex Signature (TVS); (2) the behavior of sub-tornado-scale vortices in a violent, multiple-vortex tornado (El Reno, OK – 31 May 2013); and (3) the behavior of polarimetric signatures such as the Tornado Debris Signature (TDS) and the ZDR column. Experiments in retrieving the wind field in supercells by tracking reflectivity and other miscellany may also be discussed (to fill the remainder of the time and astound the audience).

Thursday, 8 December 2016, 3:30 PM

Refreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg. 2, Main Auditorium, Room 1022

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, December 9, 2016 - 5:30am to 7:00am

Adventures in probing tornadoes and their parent supercells with mobile, rapid-scan, Doppler radars

Howard (Howie “Cb”) Bluestein
School of Meteorology, University of Oklahoma, Norman
Norman, OK

Rapid-scan Doppler radar measurements of tornadoes and their parent supercells have allowed us to view aspects of tornadogenesis that would otherwise be impossible to document because they take place on time scales too short to measure with conventional radars. During the past decade we have been using a mobile, phased array, X-band Doppler radar from the Naval Postgraduate School and a mobile, mechanically scanning, polarimetric, X-band, Doppler radar from the University of Oklahoma to make measurements during annual spring field experiments in the Plains of the U. S. In this talk I will summarize what we have learned about the following aspects of tornado behavior: (1) the origin of tornadogenesis in supercells from the perspective of the Tornadic Vortex Signature (TVS); (2) the behavior of sub-tornado-scale vortices in a violent, multiple-vortex tornado (El Reno, OK – 31 May 2013); and (3) the behavior of polarimetric signatures such as the Tornado Debris Signature (TDS) and the ZDR column. Experiments in retrieving the wind field in supercells by tracking reflectivity and other miscellany may also be discussed (to fill the remainder of the time and astound the audience).

Thursday, 8 December 2016, 3:30 PM

Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg. 2, Main Auditorium, Room 1022

First Name: 
Caroline
Last Name: 
Haws
Phone Extension (4 digits): 
8189
Email: 
haws@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, December 8, 2016 - 3:30pm to 5:00pm

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