THE TEMPORAL AND SPATIAL VARIATION OF STABLE ISOTOPES IN PRECIPITATION ON THE TIBETAN PLATEAU AND ITS ADJACENT REGIONS

The temporal and spatial variation on the stable isotopic compositions in precipitation and therelationship with temperature,precipitation and vapor sources are analyzed for the Tibetan Plateauand its adjacent regions.There is no temperature effect in the southern Tibetan Plateau and SouthAsia.Amount effect has been observed at a few sampling stations that account for about a half ofthe statistical stations.However,the seasonal variations on the stable isotopic compositions inprecipitation at those stations are inconsistent with that of precipitation intensity.There is notabletemperature effect in the middle and northern Tibetan Plateau and its adjacent Northwest China.Ithas been observed that the seasonal variations of the δO in precipitation are almost consistentwith those of air temperature in these regions.Because vapor is directly originated from low-latitude oceans,the relative heavy δO with small variation characterizes the rainfall in SouthAsia.A sharp depletion of the stable isotopic compositions in precipitation takes place fromKyangjin on the southern slop of the Himalayas to the Tanggula Mountains in the middle Plateau.The δO reaches minimum due to very strong rainout of the vapor from oceans as the vapor risesover the Himalayas.From the Tanggula Mountains to the northern Tibetan Plateau,the δO inprecipitation increases with increasing latitude and the isotopic situation in the northern Plateau istransferred into Northwest China with little disruption.