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UNSTABLE the Understanding Severe Thunderstorms and Alberta Boundary Layers Experiment ______Scientific Overview

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UNSTABLE the Understanding Severe Thunderstorms and Alberta Boundary Layers Experiment ______Scientific Overview UNSTABLE The UNderstanding Severe Thunderstorms and Alberta Boundary Layers Experiment _______________________________________ Scientific Overview Neil Taylor1, David Sills2, John Hanesiak3, Jason Milbrandt4, Craig Smith5, Pat McCarthy6, Geoff Strong7 1Hydrometeorology and Arctic Lab, Environment Canada 2Cloud Physics and Severe Weather Research Section and Nowcasting and Remote Sensing Lab, Environment Canada 3Centre for Earth Observation Science (CEOS), University of Manitoba 4Recherche en Prévision Numérique [RPN] (Numerical Weather Prediction Research Section), Environment Canada 5Climate Research Division, Environment Canada 6Prairie and Arctic Storm Prediction Centre, Environment Canada 7University of Alberta (Adjunct) 2 Table of Contents List of Figures ................................................................................................................................. 4 List of Tables .................................................................................................................................. 6 List of Abbreviations .................................................................................................................... 7 2. Rationale for UNSTABLE ........................................................................................................ 9 2.1 Socio-economic Impacts of Severe Weather in Alberta ..................................................... 9 2.2 Summer Severe Weather Forecast Challenges ............................................................... 11 2.3 Relationship to Environment Canada’s Results-Based Structure .................................... 15 2.4 Summary of Rationale for UNSTABLE ............................................................................ 17 3. Literature Review .................................................................................................................. 19 3.1 Selected Alberta Thunderstorm Research ....................................................................... 19 3.2 ABL Water Vapour and Convergence Related to CI ........................................................ 27 3.3 Land Surface - ABL Interactions and Mesoscale Circulations Related to CI and Severe Thunderstorms ...................................................................................................................... 30 3.4 High-Resolution Numerical Modelling of Alberta Thunderstorms ..................................... 31 3.5 Other Field Experiments Related to CI and Severe Thunderstorms ................................ 36 4. Project Goals and Deliverables ............................................................................................. 39 5. Science Questions ................................................................................................................ 41 5.1 ABL Processes ................................................................................................................ 41 Science Question 1: What are the contributions of ABL processes to the initiation of deep moist convection and the development of severe thunderstorms in the Alberta Foothills region? ................................................................................................................................... 41 5.2 Land Surface Interactions ................................................................................................ 47 Science Question 2: What are the contributions of surface processes to the initiation of deep moist convection and the development of severe thunderstorms in the Alberta Foothills region? ................................................................................................................................... 47 5.3 Numerical Weather Prediction ......................................................................................... 48 Science Question 3: To what extent can high-resolution numerical weather prediction models contribute to forecasting the initiation and development of severe convective storms that originate in the Alberta foothills? ............................................................................................ 48 6. Experimental Design ............................................................................................................. 51 6.1 Instrumentation and Data Collection ................................................................................ 51 6.1.1 Existing Instrumentation and Observations ................................................................... 51 6.1.2 Supplemental Mesonet Stations ................................................................................... 54 6.1.3 Supplemental Surface-Based Upper-air and Profiling Observations ............................ 55 6.1.4 Airborne Observations .................................................................................................. 56 6.1.5 Targeted Mobile Observations ...................................................................................... 57 6.1.6 Model Output from GEM-LAM-2.5 ................................................................................ 58 6.1.7 PASPC Forecasting and Nowcasting Support .............................................................. 59 6.2 UNSTABLE Study Area and Instrumentation Deployment .............................................. 59 6.2.1 UNSTABLE Domain ..................................................................................................... 59 6.2.2 Targeted Measurement Deployment Strategies ........................................................... 59 6.3 Timeframe for Field Campaign and Intensive Observation Period ................................... 62 7. Data Management ................................................................................................................. 63 8. Summary ............................................................................................................................... 64 9. References ............................................................................................................................ 66 Appendices ............................................................................................................................... 73 A1 Participants and Research Interests ................................................................................. 73 A2 Table of UNSTABLE Instrumentation ............................................................................... 75 A3 Budgeting Requirements .................................................................................................. 76 A4 UNSTABLE 2008: A Pilot Project ..................................................................................... 78 A5 Timeline and Milestones ................................................................................................... 84 3 List of Figures Figure 1: Climatological lightning activity over the Canadian Prairies showing the average number of days with at least one cloud to ground flash from 1999 to 2006 (Burrows 2006, personal communication)..............................................................................................................................9 Figure 2: (a) Population density and (b), change in population from 2001 to 2006 over southern Canada from the Statistics Canada 2006 Canadian Census. The Edmonton – Calgary corridor is among the most densely populated and fastest growing regions in Canada................................11 Figure 3: Climatological mean daily maximum dewpoint for July on the Canadian prairies for the period 1951-1980 (adapted from Smith and Yau 1993b)..............................................................12 Figure 4: Hourly surface observation sites available to forecasters over the foothills region of Alberta. The main area of thunderstorm development is west of a line from Violet Grove to Calgary. The yellow polygon denotes an area of just over 30,000 km2 within which there are no surface observations. This area also corresponds to the area with the highest occurrence of lightning days in Figure 1..............................................................................................................14 Figure 5: Eco-climatic regions of the Canadian Prairies along with Environment Canada radiosonde sites and sites at which the agrometeorological model is run (from Raddatz and Noonan 2004). The black rectangle indicated the area with significant changes in eco-climatic region described in the text...........................................................................................................15 Figure 6: 500 hPa composite maps for (a) 1200 UTC, and (b), 0000 UTC on major hail days. Heights are in m (from Longley and Thompson 1965)..................................................................19 Figure 7: 850 hPa composite maps for (a) 1200 UTC, and (b), 0000 UTC on major hail days (from Longley and Thompson 1965)......................................................................................................20 Figure 8: Seasonal variation of the number of hail days within the ALHAS study area from 1957 to 1973 (Wojtiw 1975). .....................................................................................................................20 Figure 9: Spatial distribution of average number of hail days per year from ALHAS data (adapted from Wojtiw 1975). The location of the UNSTABLE mesonet is designed to capture the main genesis region of storms that produced the maxima of hail days
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