The Characteristics Of Arid Climate Change Over North China And Eastern Northwest China

Under the background of global warming, regional aridity trend becomes more and more severity. Eastern Northwest and North China belong to the arid and semi-arid regions. In recent decades, the aridity characteristic become more and more obvious in North China, this problem has attracted by experts and scholars’attention. In this paper, firstly, the progress of the drought in North China are described.Secondly, using the precipitation and temperature measured data of53stations in North China from1958to2012, and the same period NCEP/NCAR monthly average reanalysis material. Also,using the EOF and REOF statistical method, statistical test of Mann-Kendall method,etc.analysis of precipitation in August, precipitation and temperature in summer characteristics of spatial distribution and causes in North China. Finally, using regional climate model RegCM4, single nested BCC CSM1.1global climate system model RCP4.5and RCP8.5scenario, with the eastern Northwest China to North China as the study area, simulates test and estimates the future scenario of the temperature and precipitation and drought trends.The results show that:(1) North China rainfall in August and temperature in summer EOF analysis to get the consistent as a whole, disparate into the south and the north, or the east and the west; The REOF rotated spatial patterns that anomaly sub-regional distribution characteristics of North China in precipitation and temperature. As to the temporal change trend, North China precipitation shows a decreasing trend,1986and1983-1984are the August and summer precipitation by the wetter period of transition to the dry period,respectively; the subregions nearly decades precipitation trends are inconsistent, the southern of North China has humidifying trend, northern area of warming and drying trend is most obvious, to the whole North China climatic change on main contribution. While the summer temperature shows an increasing trend in recent52years, and after the1990s warming is significant.(2) The western Pacific subtropical high and north China August precipitation have close relations. When the subtropical high intensity on the strong side and the location is shifting northward and westward, is conducive to the formation of the "west low east high" types in our latitudes500hPa, while the lower troposphere, the southerly airstream strong development will be a lot of water vapor transported northward, resulting in above normal precipitation in North China; when the subtropical high intensity on the weak side and the location is shifting eastward, resulting the North China low precipitation. Furthermore, drought trend in North China mainly due to the500hPa circulation around mid-1980s of significant adjustment and maintain. Before the mid-1980s,the North China is basically located in the west low value system and high value system in the east region of China, thus to produce precipitation. After the mid-1980s, due to the North China mainly controlled by the high value system, it is not conducive to produce precipitation. In addition,North China summer rainfall and temperatures have close relationship with sea surface temperature field, when the summer rainfall above normal over North China, the equatorial eastern Pacific, Indian Ocean and North Atlantic SST are lower, the former winter eastern equatorial Pacific SST is higher, Indian Ocean and North Atlantic SST are lower, and vice versa; When North China’s summer with high temperature, over the same period in the Western Pacific, central and eastern parts of the sea near the North Pacific, Indian Ocean and North Atlantic SST are higher, the former winter in the Western Pacific Ocean,Indian Ocean and North Atlantic SST are higher.(3) RegCM4had a certain ability to simulate temperature and precipitation in the study area, and it can simulate their spatial distribution and time trends. Future scenarios estimates, under the two scenarios,2006-2050annual average temperature in the study area showed an increasing trend from south to north; annual precipitation fluctuating trend, and precipitation begins to decrease after2041; SPI index exhibited moderate dry/wet volatile changes with no significant trend consistency, but2041-2050study areas may have a more significant drought. Among them, the future temperature under RCP8.5scenario is more obvious rising than in RCP4.5.However, under the RCP4.5scenario,annual precipitation region and the magnitude increasing larger than RCP8.5scenanio in eastern Northwest and North China.