Role of patchy snow cover on the planetary boundary layer structure during late winter observed in the central Tibetan plateau

Abstract

The one-dimensional structure of a daytime planetary boundary layer (PBL) with shallow cloud development was captured by intensive sonde observation during the late winter season at the central Tibetan Plateau (TP), and its relationship to patchy snow cover conditions was revealed. The diurnal change of potential temperature was evident in the atmosphere up to 1 km above ground, indicating PBL development, and frequent cloud formation in the afternoon and night over the PBL was confirmed by the increase of relative humidity in the sonde data profile and abrupt decrease of brightness temperature in the satellite images. Day-to-day changes of PBL and nighttime stable layer developments were dependent on the speed of the sub-tropical jet stream prevailing 5 km above the surface and the changing of snow cover conditions after snowfall events. Numerical simulations confirmed that the increase of land-surface albedo, imitating the continuous snow covers, could suppress the PBL and cloud development. The positive feedback of land-atmosphere interactions through the PBL development on patchy snow cover and re-distribution process of shallow and dry snow cover were discussed. © 2012, Meteorological Society of Japan.