Abstract

The Alberta foothills experience more thunderstorm days than any other region in the Canadian Prairie Provinces. Most storms developing there move eastward to affect the Edmonton to Calgary corridor, one of the most densely populated and fastest-growing regions in Canada. Alberta has proven to be particularly susceptible to costly thunderstorm events; Public Safety and Emergency Preparedness Canada estimate that since 1981 more than 40 lives and $2.5B have been lost due to severe storms.

Environment Canada researchers and other interested scientists from academia and the private sector have designed a field experiment over the Alberta foothills to investigate atmospheric boundary layer (hereafter ABL) processes associated with convective initiation (CI) and severe thunderstorm development. The Understanding Severe Thunderstorms and Alberta Boundary Layers Experiment (UNSTABLE) will investigate the importance of ABL water vapour availability / stratification, mesoscale convergence boundaries, land surface and ABL interactions, and numerical modeling applications to the development of severe thunderstorms over the Alberta foothills. A pilot experiment (UNSTABLE 2008) will be conducted during the summer of 2008 to test and refine measurement strategies. The full-scale UNSTABLE experiment will take place from 1 June to 31 August 2011 with a three-week intensive observation period in July. Measurements obtained through a high-resolution network of fixed and mobile surface, upper-air, and airborne instruments will be used together with measurements from existing platforms to better understand important mesoscale processes in this thunderstorm genesis zone.

The overall goals of UNSTABLE are:

To better understand atmospheric processes leading to thunderstorm development over the Alberta foothills (both prior to and during CI) with an aim to extend results to the rest of Canada
To improve accuracy and lead time for severe thunderstorm watches and warnings
To assess the ability of the Canadian GEM LAM mesoscale model to resolve physical processes over the Alberta foothills and to provide useful numerical guidance for forecasting severe convection
Through observational, case, and model studies refine existing conceptual models describing CI and the development of severe thunderstorms over Alberta and the western prairies

To address these goals three primary science questions have been formulated:

What are the contributions of ABL processes to the initiation of deep moist convection and the development of severe thunderstorms over the Alberta foothills region?
What are the contributions of surface processes to the initiation of deep moist convection and the development of severe thunderstorms over the Alberta foothills region?
To what extent can high-resolution numerical weather prediction models contribute to forecasting the initiation and development of severe convective storms that initiate in the Alberta foothills?

Associated with the above questions are a number of more specific sub-questions to be answered with data from UNSTABLE. An UNSTABLE operations plan is available from the links to the left and contains specifics related to instrument deployment, field logistics, etc.