ANALYSIS OF SOME FEATURES OF PRECIPITATION IN JULY AND AUGUST OF 1998 IN NORTHERN QINGHAI-TIBET PLATEAU
1998年夏季(7，8月)藏北降水的某些特征分析

According to the precipitation data in northern Qinghai Tibet Plateau collected during the IOP (Intense Observation Period) of GAME Tibet, some features of the precipitation (July and August) was preliminarily examined. The results showed that the distribution of summer monsoon precipitation was affected by latitude, altitude and other factors. The latitude effect of precipitation in July was more significant than the altitude effect. However, the precipitation in August not only showed latitude distribution but also showed altitude distribution to certain extent. Although July is rainy season in Qinghai Tibet Plateau, however, the surface is still relative dry and the moisture mainly comes from oceans. Thus, the large scale precipitation only resulted in insignificant altitude effect in July. In August, the wet surface and relatively strong evaporation could redistribute the precipitation. The rise activity associated with valley wind in the daytime caused by the slope heat effect could induce rise of precipitation on slopes. So such precipitation re distribution processes due to the slopes make the precipitation in August with significant altitude effect. The distribution of precipitation during July August mainly showed latitude effect but was modified by the altitude effect. Namely, the re distribution processes caused by topography make the precipitation increase with altitude at some sites. Due to the complexity of the surface conditions on Qinghai Tibet Plateau, the precipitaion was certainly controlled by a lot of factors simultaneously. It is difficult to separate simply the effect of any factor.