The importance of the correction of precipitation measurements on the Tibetan Plateau

Precipitation in the monsoon season on the Tibetan Plateau occurs as rain or snow depending on the elevation and temperature conditions. Point measurements of precipitation may not describe the accurate spatial distribution if systematic-error corrections of precipitation measurement are not applied. Precipitation data at 5 points intensively observed in the Tanggula basin (33°N, 92°E) were corrected, and the characteristics of the spatial distribution of precipitation are discussed. The largest correction was required for wind-induced loss of solid precipitation. The average ratio of corrected and measured precipitation was 1.38. An obvious increase of precipitation toward the south and higher elevations was found. Three years of precipitation data at two Chinese weather stations located north and south of the Tanggula basin were also corrected by the same methods. The ratio of corrected versus measured precipitation showed a clear annual variation, nearly constant at around 1.2 times in the monsoon season, but some months showed increase of more than 1.5 times in the non-monsoon season. Recycling of water between the atmosphere and land surface may strongly prevail in the Tibetan Plateau, which means that the corrected higher precipitation amounts directly correspond to a greater evaporation (or sensible heat source).