Assessing past and future hazardous freezing rain and wet snow events in Manitoba using a pseudo-global warming approach
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Date
2020-03-31
Authors
Tropea, Brock
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Abstract
Freezing precipitation is a major hazard across Canada. Usually occurring in the form of freezing rain and/or wet snow and can damage transportation networks, infrastructure, and vegetation. Under future warming climatic conditions, the characteristics of this precipitation may change but there is great uncertainty. This thesis characterizes damaging freezing precipitation events within Manitoba and examines their future occurrence within a warmer climate.
A total of 10 events were identified, 8 of which were within the WRF period; 5 of these had both freezing rain and wet snow, and the other 3 had freezing rain exclusively. These were characterized using data from the Japanese 55-year Reanalysis (JRA-55), several Environment and Climate Change Canada (ECCC) datasets, and two 4 km Weather Research and Forecasting (WRF) simulations from the National Center for Atmospheric Research (NCAR) from October 2000 to September 2013 (Liu et al. 2017). These were a retrospective control (CTRL) and a pseudo-global warming (PGW) simulation covering CONUS and much of Canada.
Large scale and local factors were associated with these events. Most (9 of 10) showed consistent large scale forcing: a midlatitude cyclone with 500 hPa trough and jet exit enhancing lift, low surface pressure centre nearby, and an atmospheric river. Local factors, such as the elevated terrain of Riding Mountain, influenced 2 events in CTRL and 3 in PGW by altering surface temperature and/or winds to be favourable for freezing precipitation. This terrain is also somewhat co-located with areas of severe ice loading, as shown by the Canadian Standards Association (2015).
In the PGW simulations, these events changed significantly. The 3 events with freezing rain exclusively were in December and January. Of these, 2 (1) had increased (decreased) in extent, precipitation accumulation, and duration. There was no wet snow in these events in CTRL, but it was present in PGW. The other 5 events that had both wet snow and freezing rain, and none had wet snow exclusively. Of these, 1 increased in extent, duration, and accumulation, and another increased in extent, but had similar duration and lesser accumulation. The other 3 events were reduced.
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Keywords
Meteorology, Climate, Precipitation, Freezing, Freezing rain, Wet snow, Rain, Snow, WRF, Global warming, Climate change, Model, Manitoba
Citation
American Meteorological Society