On Precipitation and Virga over Three Locations during the 1999–2004 Canadian Prairie Drought

The recent 1999-2004 drought, and especially the period from 2001 to 2002, had major impacts across Canada and in the western Canadian Prairie region in particular.This study characterizes the recent drought with respect to precipitation on a small scale at three sites: Calgary, Edmonton and Saskatoon.Climatologically, precipitation events of low daily accumulation (10 mm) account for the majority of the total accumulation (up to 58%) at all study locations.During the recent drought, these events contributed a higher proportion of the total precipitation (up to 63%) because of a lack of heavy precipitation events.Using radar data at these locations, precipitation events were also classified into three categories: convective, stratiform and virga.There was wide variation in the relative importance of stratiform and convective precipitation at the sites with, for example, some drought periods being dominated by convective and others by stratiform events.Virga was also present with an average cloud base temperature <0C which would have led to efficient sublimational loss contributing to the reduction of precipitation at the surface.Any understanding of drought must take into account such precipitation issues.