Arlette Chacón

Master's candidate at UQÀM

Supervisors: Dr. Laxmi Sushama & Dr. Hugo Beltrami
Enrolled in CREATE program in September 2012

Biophysical Impacts of Land Use Change over North America as Simulated by the Canadian Regional Climate model

This study investigates the biophysical impacts of human-induced land use change (LUC), particularly crops, on the regional climate of North America, using the fifth generation Canadian Regional Climate Model (CRCM5). To this end, two simulations are performed with CRCM5 using different land cover datasets, one corresponding to the potential vegetation and the other corresponding to current land use, spanning the 1988-2012 period and driven by ERA-Interim at the lateral boundaries. The inter-annually varying sea surface temperature and sea ice cover are also prescribed from ERA-Interim in these simulations. In the simulation with land use change, forests and grasses are replaced by crops over the mid-west United States and south-central Canada, following available land use change datasets. Therefore, surface characteristics, particularly fractional area of vegetation, leaf area index, albedo, roughness length and rooting depth, among other variables, are different in the regions of land cover change in the two simulations. Comparison of the two simulations with and without LUC suggests higher albedo values over the LUC regions in winter. This is due to the absence of crops in winter, and also possibly due to a snow-mediated positive feedback. The higher albedo values during winter are reflected in the cooler 2 meter temperature values in the simulation with LUC, compared to that with potential vegetation. Some cooling is observed in summer for the simulation with land use change, mostly due to the higher latent heat fluxes and lower sensible heat fluxes over eastern US. Increase in precipitation is noted for these regions, but are not statistically significant. The annual cycles of selected variables are further analyzed for two regions with importan LUC, i.e. central Canada and north central United States. Analysis of seasonal cycles suggests thst the cooling effect of LUC is present year round. Impact of LUC on evapotranspiration, soil moisture and precipitation are also year round. However, in the impact on runoff is mostly restricted to the snowmelt season. In summary, this study provides useful information om the impact of LUC on the climate and hydrology of North America.