利用ERA40、NCEPI(NCEP/NCAR version I)再分析资料以及高原地区的探空资料和1979年青藏高原地区第1次气象科学试验资料,详细的比较了高原地区位势高度的特征。结果表明,两套再分析资料在高原地区具有一定的相似性,但仍存在着明显的差别。相比较而言,高原北部地区ERA40再分析资料除1980—1990年在200hPa高层优于NCEPI再分析资料外,NCEPI再分析资料在年际变化上更接近探空资料;高原中部和南部地区NCEPI再分析资料除1980—1990年在200 hPa高层优于ERA40再分析资料外,ERA40再分析资料在年际变化上更接近探空资料。与1979年青藏高原地区第1次气象科学试验资料空间相关关系的比较显示,ERA40再分析资料在空间上与试验资料更相似。
The relationship of surface albedo with the solar altitude angle and soil moisture is analyzed based on two-year(January 2002 to December 2003) observational data from the AWS(Automatic Weather Sta-tion) at MS3478 in the northern Tibetan Plateau during the experimental period of CEOP/CAMP-Tibet(Coordinated Enhanced Observing Period Asia-Australia Monsoon Project on the Tibetan Plateau).As a double-variable(solar altitude angle and soil moisture) function,surface albedo varies inconspicuously with any single factor.By using the method of approximately separating the double-variable function into two,one-factor functions(product and addition),the relationship of albedo with these two factors presents much better.The product and additional empirical formulae of albedo are then preliminarily fitted based on long-term experimental data.By comparison with observed values,it is found that the parameterization formulae fitted by using observational data are mostly reliable and their correlation coeffcients are both over 0.6.The empirical formulae of albedo though,for the northern Tibetan Plateau,need to be tested by much more representative observational data with the help of numerical models and the retrieval of remote sensing data.It is practical until it is changed into effective parameterization formulae representing a grid scale in models.
Based on monthly ECMWF reanalysis-Interim(ERA-Interim) reanalysis data,along with monthly precipitation and temperature data,the Dynamic Plateau Monsoon Index(DPMI) is defined.The results of a contrast analysis of the DPMI versus the Traditional Plateau Monsoon Index(TPMI) are described.The response of general circulation to northern Qinghai-Xizang Plateau summer monsoon anomalies and the correlation of the DPMI with general circulation anomalies are investigated.The results show that,the DPMI reflected meteorological elements better and depicted climate variation more accurately than the TPMI.In years when the plateau summer monsoon is strong,the low over the plateau and the trough near the eastern coast of Asia are deeper and higher than normal over South China.This correlation corresponds to two anomalous cyclones over the plateau and the eastern coast of Asia and an anomalous anticyclone in South China.The plateau and its adjacent regions are affected by anomalous southwesterly winds that transport more moisture to South China and cause more precipitation.The lower reaches of the Yangtze River appear to receive more precipitation by means of the strong westerly water vapor flow transported from the "large triangle affecting the region".In years when the plateau summer monsoon is weak,these are opposite.The plateau monsoon is closely related to the intensity and position of the South Asian high,and the existence of a teleconnection pattern in the mid-upper levels suggests a possible linkage of the East Asian monsoon and the Indian monsoon to the plateau summer monsoon.
This study was based on the CEOP/CAMP-Tibet observed data at AWS (Automatic Weather Station) of MS3478 in the seasonal frozen soil region of northern Tibetan Plateau from March 2007 to February 2008.The variation characteristics of PE (potential evapotranspiration) were analyzed based on the Penman-Monteith method recommended by FAO (the Food and Agriculture Organization of the United Nations).The contributions of dynamic,thermal and water factors to PE were discussed,and the wet-dry condition of the plateau region was further studied.The results indicated that daily PE was between 0.52 mm and 6.46 mm for the whole year.Monthly PE was over 107 mm from May to September,but decreased to less than 41 mm from November to February.Annual PE was 1,037.8 mm.In the summer,thermal PE was significantly more than dynamic PE,but conversely in the winter.Annual variation of thermal PE was of sine wave pattern.In addition,drought and semi-drought climate lasted for a long time while semi-humid climate was short.The effect of water and dynamic factors on PE varied considerably with the seasons.Annual variation of thermal PE was of sine wave pattern.
