Comparative surface energy budgets in western and central subarctic regions of Canada

The surface energy balance was measured over two summer seasons (1996 and 1 997) at three Canadian subarctic sites. These were a wetland site in the ce ntral subarctic and a wetland and dryland site in the western subarctic. Th ese sites have similar temperature regimes but the central subarctic site r eceives twice as much rainfall as each of the western sites. The sites disp lay substantial differences in their surface characteristics. A comparison between the three study sites allows definition of the impact of surface co ntrols on the surface energy budget, for the two subarctic locations. By co mparing the evaporation rates between these three sites the surface control mechanisms at the local scale (i.e. microtopography, vegetation cover and organic layer thickness) can be examined relative to the larger scale geogr aphical factors. The two wetland sites demonstrated similar evaporation beh aviour but the dryland evaporates substantially less. This similarity in we tland evaporation in spite of major differences in rainfall and standing wa ter demonstrates the importance of the surface organic layer in transportin g and storing water for evaporation. The magnitude of convective and conduc tive heat fluxes is strongly correlated with temperature in both regions. W arm temperatures enhance the latent and ground heat fluxes while suppressin g the sensible heat flux at all sites. Cold temperatures have the opposite effect. Copyright (C) 2000 Royal Meteorological Society.