Soil moisture variations are a very important part of the hydrological budget at high latitudes, affecting evapotranspiration, runoff, and water table. Current land-surface parameterizations treat the frozen soil in a very crude way, if at all, but the way that the soil freezes in the fall can have large impacts on the fraction of water that infiltrates in the spring, with large effects on spring runoff and summer soil water availability. Using a unique data set of more than 20 Russian energy-balance and water-balance stations, we investigate the interannual variations of soil moisture as a function of the state of the soil. These stations have actual gravimetric soil moisture observations made every 10 days when the ground is not frozen, and every month when it is, for many years, as well as observations of depth of frozen ground and all meteorological observations. By comparing the weather with the frozen soil data and soil moisture data, we evaluate the role of freezing on soil moisture variations, and the role of intermittent warmings and of condensation. We also show an improved land surface model, that explicitly accounts for the freezing and significantly improves the simulations as compared to existing models.

Prof. Alan Robock
Department of Meteorology
University of Maryland
College Park, MD  20742
Phone: (301) 405-5377
Fax: (301) 314-9482
Email: alan@atmos.umd.edu
http://www.meto.umd.edu/~alan