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Past MMM Events

Kevin Ash NCAR/MMM/ASP 

Extreme weather and climate events continue to plague the United States in tandem with increased societal exposure and susceptibility stemming from higher population densities in hazardous locations and the exacerbated frequency and intensity of some hazards in association with anthropogenic climate change.  In this presentation I will focus on severe thunderstorm hazards, and specifically on risk perception, vulnerability, & communication in the tornado context.  Despite advances in forecasting and detection of severe thunderstorms over the past several decades, the calendar year 2011 saw over 500 deaths from tornadoes in the United States for the first time since 1953.  These events renewed interest in social science research related to severe thunderstorm hazards in order to better understand how people perceive danger from tornadoes and act (or fail to act) to protect themselves and their families when tornadoes threaten.

I will highlight two of my recent research projects and connect these to my current research.  The first seeks to understand how people interpret and potentially act upon spatially explicit visual depictions of tornado warnings.  Survey participants viewed and responded to hypothetical warning maps with varying representations of risk at locations distributed evenly across the maps.  The results suggest several key concepts for spatially explicit risk communication to elicit appropriate and timely protective action.  The second research project focuses on manufactured housing residents, an especially vulnerable sub-population which comprises nearly half of tornado fatalities.  The project used a mixed method research design to better understand why very few manufactured housing residents follow the recommendation to evacuate to a tornado shelter or other sturdy building during a tornado warning.  Based on interviews and survey data, many residents do not believe their manufactured home to be an unsafe sheltering location, while others who would like to evacuate are often very uncertain about appropriate timing and destinations for evacuation.  I will conclude by discussing how future work will incorporate risk perception, vulnerability, and communication within a single geospatial modeling framework.  

Refreshments: 3:15 PM

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, January 19, 2018 - 5:30am to 6:30am

Kevin Ash
NCAR/MMM/ASP 

Extreme weather and climate events continue to plague the United States in tandem with increased societal exposure and susceptibility stemming from higher population densities in hazardous locations and the exacerbated frequency and intensity of some hazards in association with anthropogenic climate change.  In this presentation I will focus on severe thunderstorm hazards, and specifically on risk perception, vulnerability, & communication in the tornado context.  Despite advances in forecasting and detection of severe thunderstorms over the past several decades, the calendar year 2011 saw over 500 deaths from tornadoes in the United States for the first time since 1953.  These events renewed interest in social science research related to severe thunderstorm hazards in order to better understand how people perceive danger from tornadoes and act (or fail to act) to protect themselves and their families when tornadoes threaten.

I will highlight two of my recent research projects and connect these to my current research.  The first seeks to understand how people interpret and potentially act upon spatially explicit visual depictions of tornado warnings.  Survey participants viewed and responded to hypothetical warning maps with varying representations of risk at locations distributed evenly across the maps.  The results suggest several key concepts for spatially explicit risk communication to elicit appropriate and timely protective action.  The second research project focuses on manufactured housing residents, an especially vulnerable sub-population which comprises nearly half of tornado fatalities.  The project used a mixed method research design to better understand why very few manufactured housing residents follow the recommendation to evacuate to a tornado shelter or other sturdy building during a tornado warning.  Based on interviews and survey data, many residents do not believe their manufactured home to be an unsafe sheltering location, while others who would like to evacuate are often very uncertain about appropriate timing and destinations for evacuation.  I will conclude by discussing how future work will incorporate risk perception, vulnerability, and communication within a single geospatial modeling framework.  

Refreshments: 3:15 PM

First Name: 
Bobbie
Last Name: 
Weaver
Phone Extension (4 digits): 
8946
Email: 
weaver@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, January 18, 2018 - 3:30pm to 4:30pm

Joseph Olson Global Systems Division NOAA--Earth System Research Laboratory 

The Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) are NOAA real-time operational hourly updating forecast systems run at 13- and 3-km grid spacing, respectively. Both systems use the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) as the model component of the forecast system. During the second installment of the Wind Forecast Improvement Project (WFIP 2), the RAP/HRRR have been targeted for the improvement of low-level wind forecasts in the complex terrain within the Columbia River Basin (CRB), which requires much finer grid spacing to resolve important topographic features in/near the CRB. Therefore, this project provides a unique opportunity to test and develop the RAP/HRRR physics suite within a very high-resolution nest (∆x = 750 m) over the northwestern US. Special effort is made to incorporate scale-adaptive flexibility into the RAP/HRRR physics suite, with emphasis on the representation of subgrid-scale boundary layer and orographic drag processes.

Many wind profiling and scanning instruments have been deployed in the CRB in support the WFIP 2 field project, which spanned 01 October 2015 to 31 March 2017. During the project, several forecast error modes were identified, such as: (1) too-shallow cold pools during the cool season, which can mix-out more frequently than observed and (2) the low wind speed bias in thermal trough-induced gap flows during the warm season. Development has been focused on improving these common forecast failure modes with the criteria of achieving at least neutral impacts in all other operational forecast objectives. This presentation will highlight the testing and development of various model components, showing the improvements over original RAP/HRRR physics. Examples of case studies and retrospective periods will be presented to illustrate the improvements.  Ongoing and future challenges in RAP/HRRR physics development will be touched upon.

Refreshments: 3:15 pm

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, December 1, 2017 - 5:30am to 6:30am

Joseph Olson
Global Systems Division
NOAA--Earth System Research Laboratory 

The Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) are NOAA real-time operational hourly updating forecast systems run at 13- and 3-km grid spacing, respectively. Both systems use the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) as the model component of the forecast system. During the second installment of the Wind Forecast Improvement Project (WFIP 2), the RAP/HRRR have been targeted for the improvement of low-level wind forecasts in the complex terrain within the Columbia River Basin (CRB), which requires much finer grid spacing to resolve important topographic features in/near the CRB. Therefore, this project provides a unique opportunity to test and develop the RAP/HRRR physics suite within a very high-resolution nest (∆x = 750 m) over the northwestern US. Special effort is made to incorporate scale-adaptive flexibility into the RAP/HRRR physics suite, with emphasis on the representation of subgrid-scale boundary layer and orographic drag processes.

Many wind profiling and scanning instruments have been deployed in the CRB in support the WFIP 2 field project, which spanned 01 October 2015 to 31 March 2017. During the project, several forecast error modes were identified, such as: (1) too-shallow cold pools during the cool season, which can mix-out more frequently than observed and (2) the low wind speed bias in thermal trough-induced gap flows during the warm season. Development has been focused on improving these common forecast failure modes with the criteria of achieving at least neutral impacts in all other operational forecast objectives. This presentation will highlight the testing and development of various model components, showing the improvements over original RAP/HRRR physics. Examples of case studies and retrospective periods will be presented to illustrate the improvements.  Ongoing and future challenges in RAP/HRRR physics development will be touched upon.

Refreshments: 3:15 pm

First Name: 
Bobbie
Last Name: 
Weaver
Phone Extension (4 digits): 
8946
Email: 
weaver@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, November 30, 2017 - 3:30pm to 4:30pm

William SkamarockNCAR/MMM 

One of the unsolved questions in atmospheric dynamics concerns the energetics responsible for the horizontal wavenumber k^(-5/3) scaling observed in the mesoscale portion of the atmospheric kinetic energy (KE) spectrum.  Model spectra qualitatively reproduce the observations-based spectrum in both the synoptic-scale k^(-3) and mesoscale k^(-5/3) regions, and given the limitations of the observations, modeling-based studies have become the primary approach for examining the mesoscale dynamics of the spectrum.  We are computing atmospheric spectra for global NWP forecasts using the atmospheric component of the Model for Prediction Across Scales (MPAS) to study these dynamics.  As in past studies, we find a mesoscale region in the model spectrum when resolution is sufficiently fine.  The first part of the present study examines the accuracy of model solutions, where we find that typical model configurations produce solutions that are significantly under-resolved vertically as revealed in convergence test results for KE spectra and examination of inertia gravity wave structure.  The second part of this study examines KE dissipation and its associated dynamics.  The mesoscale region is thought to be characterized as possessing a net downscale energy cascade, and the dynamics in the regions of energy dissipation should play a role in the downscale cascade.   Understanding these dynamics should help test existing theories for the mesoscale KE spectrum.  We will present results illustrating these points,  and we will discuss the implications of these results for current theories for the mesoscale KE spectrum.  We will also discuss the implications for atmospheric modeling applications in weather and climate given that current operational weather and climate model configurations do not resolve well the mesoscale KE, particularly in the upper troposphere and lower stratosphere.

Refreshments: 3:15 pm

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, December 8, 2017 - 5:30am to 6:30am

William Skamarock
NCAR/MMM 

One of the unsolved questions in atmospheric dynamics concerns the energetics responsible for the horizontal wavenumber k^(-5/3) scaling observed in the mesoscale portion of the atmospheric kinetic energy (KE) spectrum.  Model spectra qualitatively reproduce the observations-based spectrum in both the synoptic-scale k^(-3) and mesoscale k^(-5/3) regions, and given the limitations of the observations, modeling-based studies have become the primary approach for examining the mesoscale dynamics of the spectrum.  We are computing atmospheric spectra for global NWP forecasts using the atmospheric component of the Model for Prediction Across Scales (MPAS) to study these dynamics.  As in past studies, we find a mesoscale region in the model spectrum when resolution is sufficiently fine.  The first part of the present study examines the accuracy of model solutions, where we find that typical model configurations produce solutions that are significantly under-resolved vertically as revealed in convergence test results for KE spectra and examination of inertia gravity wave structure.  The second part of this study examines KE dissipation and its associated dynamics.  The mesoscale region is thought to be characterized as possessing a net downscale energy cascade, and the dynamics in the regions of energy dissipation should play a role in the downscale cascade.   Understanding these dynamics should help test existing theories for the mesoscale KE spectrum.  We will present results illustrating these points,  and we will discuss the implications of these results for current theories for the mesoscale KE spectrum.  We will also discuss the implications for atmospheric modeling applications in weather and climate given that current operational weather and climate model configurations do not resolve well the mesoscale KE, particularly in the upper troposphere and lower stratosphere.

Refreshments: 3:15 pm

First Name: 
Bobbie
Last Name: 
Weaver
Phone Extension (4 digits): 
8946
Email: 
weaver@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, December 7, 2017 - 3:30pm to 4:30pm

Raymond A. ShawAtmospheric Sciences Program Michigan Technological University 

Aerosol particles, such as sea salt, dust and anthropogenic pollution, influence the optical properties of clouds and the tendency of a cloud to form precipitation through droplet collisions. We have investigated cloud droplet growth in a turbulent environment under varying levels of aerosol concentration. The results reveal a surprising role of turbulence in cloud droplet growth that leads to two regimes: a polluted cloud regime in which thermodynamic conditions are rather uniform and cloud droplet sizes are similar, and a clean cloud regime in which thermodynamic conditions are highly variable and cloud droplet sizes are very diverse. The narrowing of droplet size range under polluted conditions introduces a new stabilizing factor by which increased aerosol concentration can suppress precipitation and enhance cloud brightness. 

Cloud droplet growth in a turbulent environment is studied by creating turbulent moist Rayleigh-Benard convection in a laboratory chamber (the Pi Chamber). Cloud formation is achieved by injecting aerosols into the water-supersaturated environment created by the isobaric mixing of saturated air at different temperatures. In steady state, the injection and activation of aerosol particles to form cloud droplets is balanced by cloud droplet growth through vapor condensation and loss by gravitational settling. A range of steady-state cloud droplet number concentrations is achieved by supplying aerosols at different rates. As steady-state droplet number concentration is decreased the mean droplet size increases as expected, but also the width of the size distribution increases. This increase in the width is associated with larger supersaturation fluctuations due to the slow droplet microphysical response (sink of the water vapor) compared to the fast turbulent mixing (source of the water vapor). The boundary between the two regimes can be identified with a cloud Damkoehler number of order unity.

Thursday, 16 November 2017, 3:30 PM Refreshments:  3:15 PM

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, November 17, 2017 - 5:30am to 6:30am

Raymond A. Shaw
Atmospheric Sciences Program
Michigan Technological University 

Aerosol particles, such as sea salt, dust and anthropogenic pollution, influence the optical properties of clouds and the tendency of a cloud to form precipitation through droplet collisions. We have investigated cloud droplet growth in a turbulent environment under varying levels of aerosol concentration. The results reveal a surprising role of turbulence in cloud droplet growth that leads to two regimes: a polluted cloud regime in which thermodynamic conditions are rather uniform and cloud droplet sizes are similar, and a clean cloud regime in which thermodynamic conditions are highly variable and cloud droplet sizes are very diverse. The narrowing of droplet size range under polluted conditions introduces a new stabilizing factor by which increased aerosol concentration can suppress precipitation and enhance cloud brightness. 

Cloud droplet growth in a turbulent environment is studied by creating turbulent moist Rayleigh-Benard convection in a laboratory chamber (the Pi Chamber). Cloud formation is achieved by injecting aerosols into the water-supersaturated environment created by the isobaric mixing of saturated air at different temperatures. In steady state, the injection and activation of aerosol particles to form cloud droplets is balanced by cloud droplet growth through vapor condensation and loss by gravitational settling. A range of steady-state cloud droplet number concentrations is achieved by supplying aerosols at different rates. As steady-state droplet number concentration is decreased the mean droplet size increases as expected, but also the width of the size distribution increases. This increase in the width is associated with larger supersaturation fluctuations due to the slow droplet microphysical response (sink of the water vapor) compared to the fast turbulent mixing (source of the water vapor). The boundary between the two regimes can be identified with a cloud Damkoehler number of order unity.

Thursday, 16 November 2017, 3:30 PM
Refreshments:  3:15 PM

First Name: 
Bobbie
Last Name: 
Weaver
Phone Extension (4 digits): 
8946
Email: 
weaver@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, November 16, 2017 - 3:30pm to 4:30pm

Richard Rotunno NCAR/MMM 

From the point of view of the shallow-water equations (SWE), the hydraulic jump is a discontinuity in fluid-layer depth and velocity at which kinetic energy is dissipated. To provide an understanding of the origin and internal dynamics of the hydraulic jump, three-dimensional numerical solutions of the Navier-Stokes Equations (NSE) are carried out alongside SWE solutions for nearly identical physical initial-value problems. Analysis of the solutions to the initial-value problem shows that the tendency to form either the lee-side height/velocity discontinuity in the SWE, or the overturning density interface in the NSE, is a feature of inviscid, nonturbulent fluid dynamics. Dissipative turbulent processes associated with the lee-side hydraulic jump are a consequence of the inviscid fluid dynamics that initiate and maintain the locally unstable conditions. Implications for the modeling of atmospheric mountain waves and lee vortices are discussed.

Refreshments:  3:15 PM

Building:
Room Number: 
1022
Type of event:
Will this event be webcast to the public by NCAR|UCAR?: 
Calendar Timing: 
Friday, November 10, 2017 - 5:30am to 6:30am

Richard Rotunno
NCAR/MMM 

From the point of view of the shallow-water equations (SWE), the hydraulic jump is a discontinuity in fluid-layer depth and velocity at which kinetic energy is dissipated. To provide an understanding of the origin and internal dynamics of the hydraulic jump, three-dimensional numerical solutions of the Navier-Stokes Equations (NSE) are carried out alongside SWE solutions for nearly identical physical initial-value problems. Analysis of the solutions to the initial-value problem shows that the tendency to form either the lee-side height/velocity discontinuity in the SWE, or the overturning density interface in the NSE, is a feature of inviscid, nonturbulent fluid dynamics. Dissipative turbulent processes associated with the lee-side hydraulic jump are a consequence of the inviscid fluid dynamics that initiate and maintain the locally unstable conditions. Implications for the modeling of atmospheric mountain waves and lee vortices are discussed.

Refreshments:  3:15 PM

First Name: 
Bobbie
Last Name: 
Weaver
Phone Extension (4 digits): 
8946
Email: 
weaver@ucar.edu
Building:
Room Number: 
1022
Host lab/program/group:
Type of event:
Calendar Timing: 
Thursday, November 9, 2017 - 3:30pm to 4:30pm

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