On the Annual Cycle in Surface Pressure on the Tibetan Plateau Compared to Its Surroundings

Abstract

The authors have investigated the climatological annual cycle in surface pressure on the Tibetan Plateau in relation to the annual cycle in surface pressure at the lower surroundings (India and China). It is found that surface pressure on the plateau is low (high) when the surrounding Asian continent has high (low) pressure. This out-of-phase relationship is evident in the NMC analyses and in long runs made with the NMC's global model. The authors have also found a few station observations on the plateau that have partially confirmed these opposing annual cycles in surface pressure. The authors believe this contrast to be real and operative over other parts of the globe as well. Near mean sea level, the surface pressure is low (high) when the temperature is high (low) (relative to its surroundings). At higher elevations, pressure is low (high) when temperatures are low (high). Also, in the datasets studied, the authors found no evidence for a thermal low on top of the plateau in summer.