Storms and Precipitation Across the Continental Divide Experiment

PI: Julie Theriault, University of Quebec at Montreal

Project Coordinator: Juris Almonte

Co-I's: Stephen Déry, University of Northern British Columbia; Shawn Marshall, University of Calgary; John Pomeroy, University of Saskatchewan; Ronald Stewart, University of Manitoba

This project focuses on cold region processes related to storms and their precipitation at the top of the western Cordillera. The precipitation in this region provides the primary source of water for North American rivers going to the Pacific, Atlantic and Arctic Oceans, can trigger catastrophic flooding and it maintains the perilous existence of glaciers. Despite its essential role, very few observations that link surface features, precipitation and atmospheric conditions are available in this region. This project will start to address this gap by using a combination of sophisticated weather instruments, instrumented mountain basins and modelling tools to study storms and precipitation across the continental divide. One of the key issues is how much of the moisture flux crosses the barrier from either the Pacific in eastward moving storms or from the Prairies and Gulf of Mexico in leeside (upslope) storms. In particular, small-scale features of this moisture transport such as the distribution of snowfall, from for example, preferential deposition, will be addressed. To do so, both sides of the divide will be instrumented to measure precipitation fields aloft to study their evolution as they fall through the atmosphere on either side of the divide. The study region includes well-documented glacier sites as well as mountain headwater basins that were sources of the 2013 floodwaters in Alberta and British Columbia. This fills in the gaps of efforts to characterize the precipitation at the surface and snowline, in drought periods and will help determine their impacts on hydrology as part of GWF. Although our team is involved in GWF Pillar 3 projects (JT/RS: 2 projects, SD: 1 project and JP: 6 projects), none is obtaining any special atmospheric measurements or examining small-scale features of orographic precipitation. A critical outcome will be to deliver a system to diagnose and predict precipitation amounts, patterns and types across the divide using a combination of very high-resolution modelling and sophisticated instrumentation. This will inform improvements in numerical weather prediction systems such as Global Environmental Multiscale (GEM) model.