Region Change of Asian Arid and Semiarid Area in Recent Years
|Keywords||Asian arid / semi- arid areas Ocean warm pool ENSO Water vapor Precipitation The top of the troposphere Cloud Cover coverage CCM3|
In this paper, the ERA-40 reanalysis data analysis of the climatic characteristics of Asian arid / semi- arid areas , wet mechanism of precipitation and oceanic warm pool climate characteristics, and in the study area . The results show that : the Asian arid / semi- arid areas excluding the seasonal variation of water vapor , precipitation with three oceans the warm pool (WPWP, EIOWP and the EP) zone between 10 ° latitude north and south regional water vapor , sea surface temperature has a very significant positive correlation between . Arid / semi- arid areas of precipitation and the eastern Indian Ocean warm pool SST correlation is best , and the Western Pacific Warm Pool , followed by a weak correlation with the Area El Nino1 2 ; El Nino zone is closer Pacific , Asia arid area with ElNino moisture , the stronger the correlation . Asian arid / semi- arid areas in summer precipitation and EIOWP1 WPWP1 / 2 and the EP three oceans warm pool seasons SST has a good correlation ; Asian arid / semi-arid zones the precipitation of EIOWP1 sea temperature change in response to the most the fast sea surface temperature changes ( changes in precipitation postponed from January to March ) , the slowest response WPWP1 / 2 SST changes ( delay of four months) . Summer in the Winter of El Nino and La Nina years , the seasonal scale , Asian arid / semi- arid areas of precipitation than normal years . The analysis also shows that in recent years due to the westerly winds weaken and the enhancement of the Indian monsoon , makes more Indian monsoon and East Asian monsoon region water vapor is transported to the Asian arid / semi- arid areas , water vapor increases over the arid region , one of the reasons for the increase in precipitation high cloud cover of the study area weakened in recent years , but in low cloud cover increased, indicating that the low-level convergence increases in precipitation ; analysis of the top of the troposphere and the lower the temperature trend found lower troposphere temperature rises , while the top-level temperature decreased this temperature variation can exacerbate the atmospheric convective activity in the troposphere , conducive to the formation of precipitation . We also do three control experiments show that the sea surface temperature (SST) increased over the study area, the water vapor will in turn increase .