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McGill University (2004)

A study of drought characteristics over the Canadian Prairies

Roberts, Erin

Titre : A study of drought characteristics over the Canadian Prairies

Auteur : Roberts, Erin

Université de soutenance : McGill University

Grade : Master of Science 2004

Résumé
Typically, drought occurs once every three years across the Canadian Prairies. Most research addressing such droughts has concentrated on the large scale conditions associated with this form of extreme weather whereas little research has been conducted on its smaller scale characteristics. The present research begins to address the latter issue. Several datasets (surface observations, drought indices, and re-analysis products) were used to identify and analyze the 11 most severe droughts occurring over the Prairies since 1953. Warm season hourly surface observations (temperature, moisture, clouds, and precipitation) from 10 observational sites were then compared for extreme drought, drought, non-drought, and extreme wet conditions. When compared to non-drought or extreme wet conditions, drought and extreme drought conditions are associated with warmer temperatures and drier conditions and there is little change in the amount of total cloud cover but cloud bases are higher. As well, the maximum temperature and highest cloud base both occur 1-2 h later in the afternoon during drought and extreme drought conditions as compared to non-drought and extreme wet conditions. Such factors act to extend the drought conditions. For example, the higher cloud bases during drought and extreme drought conditions lead to greater evaporation of falling precipitation and this prevents significant precipitation from occurring thereby reinforcing the dry conditions.

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Page publiée le 20 mai 2011, mise à jour le 6 février 2018