Precipitation characteristics and associated weather conditions on the eastern slopes of the Canadian Rockies during March–April 2015

Thériault, Julie M.; Hung, Ida; Vaquer, Paul; Stewart, Ronald E. et Pomeroy, John W. (2018). « Precipitation characteristics and associated weather conditions on the eastern slopes of the Canadian Rockies during March–April 2015 ». Hydrology and Earth System Sciences, 22(8), pp. 4491-4512.

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Résumé

Precipitation events that bring rain and snow to the Banff–Calgary area of Alberta are a critical aspect of the region's water cycle and can lead to major flooding events such as the June 2013 event that was the second most costly natural disaster in Canadian history. Because no special atmospheric-oriented observations of these events have been made, a field experiment was conducted in March and April 2015 in Kananaskis, Alberta, to begin to fill this gap. The goal was to characterize and better understand the formation of the precipitation at the surface during spring 2015 at a specific location in the Kananaskis Valley. Within the experiment, detailed measurements of precipitation and weather conditions were obtained, a vertically pointing Doppler radar was deployed and weather balloons were released. Although 17 precipitation events occurred, this period was associated with much less precipitation than normal (−35%) and above-normal temperatures (2.5°C). Of the 133h of observed precipitation, solid precipitation occurred 71% of the time, mixed precipitation occurred 9% and rain occurred 20%. An analysis of 17504 precipitation particles from 1181 images showed that a wide variety of crystals and aggregates occurred and approximately 63% showed signs of riming. This was largely independent of whether flows aloft were upslope (easterly) or downslope (westerly). In the often sub-saturated surface conditions, hydrometeors containing ice occurred at temperatures as high as 9°C. Radar structures aloft were highly variable with reflectivity sometimes  > 30dBZe and Doppler velocity up to −1ms−1, which indicates upward motion of particles within ascending air masses. Precipitation was formed in this region within cloud fields sometimes having variable structures and within which supercooled water at least sometimes existed to produce accreted particles massive enough to reach the surface through the relatively dry sub-cloud region.

Type:	Article de revue scientifique
Informations complémentaires:	© Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License.
Mots-clés ou Sujets:	Precipitation characteristics, Precipitation events, Natural disasters, Doppler radar, Meteorological baloons, Canadian Rockies, Kananaskis Valley
Unité d'appartenance:	Centres institutionnels > Centre pour l'étude et la simulation du climat à l'échelle régionale (ESCER) Faculté des sciences > Département des sciences de la Terre et de l'atmosphère
Déposé par:	Julie Mireille Thériault
Date de dépôt:	12 sept. 2018 08:05
Dernière modification:	06 mars 2019 09:22
Adresse URL :	http://archipel.uqam.ca/id/eprint/11600

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