关键词: 赤道中东太平洋, 关键区海温, 宁夏春季降水

Abstract: Based on data of Ningxia 24 meteorological stations spring precipitation in recent 53 years,Niño1+2 and Niño3.4 index of monthly mean sea surface temperature(SST)in the period of 1961-2013 obtained from American climate forecast center,and reanalysis monthly 500hPa height form NCEP/NCAR,using empirical orthogonal function(EOF)and running correlation analysis methods studies the spatial distribution and time evolution of spring precipitation in Ningxia,and studies furtherly how the Pacific SST in the key area of the Equator middle-east influence the precipitation through the western Pacific subtropical high and 500 hPa atmospheric circulation over middle-high latitude. The study result shows that,in recent 53 years,the uniform more or less precipitation anomaly patterns of spring precipitation in Ningxia accounts for more than 70%,in which the uniform less pattern accounts for 43% and uniform more pattern accounts for 27%. The second anomaly pattern is of north less and south more precipitation,which accounts for 21%,and the opposite pattern accounts for 7%. In further it finds that the key area SST of Equator middle-east Pacific in previous summer-autumn persisting correlates significantly to the subsequently spring precipitation in Ningxia during 5-8 months. The correlation coefficients are higher to the previous July to September SST with correlation coefficients gradually increasing. Through air-sea interaction,the key area SST anomalies of Equator middle-east Pacific influence the 500 hPa height anomaly atmosphere circulation and location of the western Pacific subtropical high,and these two influence the water vapor sources and spatial distribution of subsequently spring precipitation of Ningxia. Corresponding to years of previous summer-autumn warmer SST in Niño1+2 area of equator middle-east Pacific,in the subsequent spring, it is always found the positive and negative height anomaly centers,e.g.+-+pattern on 500 hPa level in the middle-high latitude,with negative height anomaly over a wide region around Baikal Lake and west of there. And accompanying with trough depth and Ningxia locates in front of it and positive anomaly near Japanese sea. Then it forms the west low and east high pattern,which is advantage of the forming stable precipitation. If the previous SST is cooler,the East Asian trough depths on 500 hPa level in subsequent spring,in this atmosphere circulation configuration pattern Ningxia locates in west high and east low pattern,which is not advantage to precipitation. In further through statistic it is found in most cases,if previous year summer-autumn Niño1+2 SST anomaly is warmer,in the subsequent spring the Western Pacific subtropical high ridge line position and the northern boundary is normal north,west ridge point obviously to the west,with more than 50% years to 100°E West,and Ningxia is in the southwest airflow of the west side of the West Pacific subtropical high,which is advantage to precipitation. If previous summer-autumn Niño1+2 SST anomaly is cooler,in the subsequent spring the northern boundary of Western Pacific subtropical high is significant south and ridge line position normal south,west ridge point obviously to the east,with more than 50% years to 100°E east,and in which 42% years is over around 166°E. In this case the water vapor channel is blocked and not advantage to induce precipitation.

Key words: the central and eastern equatorial Pacific, the key to the SST, spring precipitation in Ningxia