Effect of 1-km Subgrid Land-Surface Heterogeneity on the Multi-year Simulation of RCM-Modelled Surface Climate Over the Region of Complex Topography

Effects of parameterization of subgrid-scale topography and land cover scheme (SubBATS) at 1-km resolution were investigated over the Alpine region using a regional climate model. Two multi-year simulations were carried out with the Regional Climate Model of International Centre for Theoretical Physics. The control simulation was carried out at 10-km horizontal resolution using standard land-surface model; while for the SubBATS simulation, the land-surface model was employed at much higher resolution (1 km) to investigate the effect of land-surface heterogeneity on the Alpine climate. In SubBATS, near-surface atmospheric state variables from coarse (10-km) atmospheric model were disaggregated to 1 km before passing to high-resolution land surface scheme. Comparison of these two multi-year simulation was done for the Great Alpine Region. The analysis shows the added value imparted by very high-resolution SubBATS in simulating hydrology processes in the complex terrain. The direct effects of the scheme are evident on height-dependent variables; temperature and snow pack. The better representation of topographic height in sub-scale scheme leads to more refined temperature field which subsequently results in more realistic representation of snow cover and snow melt. At 1-km resolution, the influence of resolved mountain peaks and valleys results in decrease of snow-covered area. The subgrid scheme not only improves the overall simulation by feedback process but also provides high-resolution meteorological fields that can be used for adaptation and impact studies. Therefore, more accurate representation of land-surface heterogeneity in sub-grid approach improves the temperature and snow fields over the complex terrain and can be useful for coupling with impact models, although further improvements are desirable.