Snowmelt and Atmospheric Heating Processes over Eastern Mongolia

Abstract

A shallow snowpack, such as that seen in Mongolia, easily melts through heating by the atmosphere. In turn, a snow-free surface without much meltwater heats the atmosphere quickly through heat fluxes at the surface. The present study investigated the snowmelt processes over eastern Mongolia during 2005-2007, using ground-observed temperature, snow depth, albedo, and radiation data. Moreover, we explored atmospheric influences on the snowmelt through the heat budget analysis of reanalysis data provided by the National Centers for Environmental Prediction.
The results show that atmospheric heating over eastern Mongolia during the snowmelt season is caused by the combination of vertical adiabatic heating in a traveling anticyclone and one-day-lagging horizontal advection after the passage of the anticyclone. These synoptic processes lead to a drastic increase in temperature and finally to substantial snowmelt under certain atmospheric conditions: the daily-mean surface air temperature exceeding -10°C and downward longwave radiation exceeding 194 W m^-2 under clear sky conditions.