A Study On Some Problems Of The Climate Change Of Global Land Precipitation For March-May During 1948-2001

Using the global land three months monthly data (PREC/L)created by Chen et al(2001),NCEP/NCAR reanalyzed monthly mean wind data and global monthly SST grid data edited by British Meteorological Bureau, this paper investigates some problems of the climate change of global land rainfall for March-May during 1948-2001.The time distribution feature of rainfall trend for global land seasonal and monthly rainfall indicates that the rainfall in global land areas is characterized by the negative trend variation. The interannual and interdecadal fluctuations of the rainfall are clear. The late 1940s-early 1960s and early 1970s to middle 1980s is wet period. The early 1960s to early 1970s is dry period. The significant decrease of rainfall began in the 1990s.The analysis on the spatial distribution feature of rainfall trend for global land seasonal and monthly rainfall points out that the mainly regions of increasing precipitation are north of Canada, east of Greenland, southeast of South America, mid-west of Australia, from Newland to north of Siberian in northern Ural and west of Europe. It's found that the negative trend of precipitation in southeast of Canada, west of South America, Middle East to SinKiang of China, north and west of Africa, southeast of China, east of Russia, south of Australia and the most of Antarctica.The study on the distribution feature of global land rainfall for March-May during 1948-2001 points out that the maximum precipitation occurs in the monsoon areas, and their standard deviation is bigger in monsoon areas thanthe others. The distribution of the rainfall is continuous along the latitude belts.According normal divides and identifies the drought and flood years of large-scale areas for during March-May. Results show that the connection is close between drought (flood) years and warm(cold) events in large-scale areas. The distribution of drought and flood years shows significant decadal feature.The relations between rainfall fields during March-May and wind fields, SST and ENSO are discussed primarily. Results show that the corresponding relations are significant between the feature of drought and flood years in significant abnormal regions of precipitation and changes of the same period three wind fields. In addition, the changes of drought and flood during March-May are coherent with SST. ENSO has a significant influence on abnormal precipitation of global during March-May. In the most of areas in global land, the average precipitation in EINino years is decreasing, the average precipitation in LaNina years is increasing.