Influence of open water bodies on the modelling of summertime convection over the Canadian Prairies

Abstract

here are numerous water features on the Canadian landscapes that are not monitored. Specifically, there are water bodies over the prairies and Canadian shield regions of North America that are ephemeral in nature and could have a significant influence on convective storm generation and local weather patterns through turbulent exchanges of sensible and latent heat between the land and the atmosphere. In this study we perform a series of numerical experiments with Environment Canada?s GEM (Global Environmental Multiscale) model at 2.5-km grid spacing to examine the sensitivity of the atmospheric boundary layer and the resulting precipitation to the presence of open water bodies.Operationally, the land-water fraction in GEM is specified by means of static geophysical databases which do not change with time. Uncertainty is introduced in this study into this land-water fraction and the sensitivity of the resulting precipitation is quantified for a convective precipitation event occurring over the Canadian prairies in the summer of 2014. The results indicate that with an increase in open water bodies, accumulated precipitation, peak precipitation amounts and intensities decrease. Moreover, shifts are seen in times of peak for both precipitation amounts and intensities, in the order of increasing wetness. Additionally, with an increase in open water bodies, Convective Available Potential Energy (CAPE) decreases and Convective Inhibition (CIN) increases, indicating suppression of forcing for convective precipitation.