A Study On The Relationship Between Summer Precipitation In Shandong And SSTA Of Pacific Together With Atmospheric Circulations In East Asia

Summer is the very season whose rainfall is the most of the whole year in Shandong Province, thus it is also the key period concerning to the whole year's drought/flood situation. The spatial and temporal characterisyics of summer rainfall are analyzed by using the the monthly precipitation data from 26 weather stations in Shandong province. The rainfall inclines from the southeast to northwest of the province both in summer and each month of summer. The distrbutions of rainfall in summer and July are almost the same. There are interannual variations in summer rainfall in Shandong province, especially in July, and the oscillation period is about 2.2-3.4 years.Based on the Coads SST data and precipitation data from 26 weather stations in Shandong from 1961 to 1999,we caculated the correlation coefficient and find that rainfall of summer in Shandong province is closely related to the sea surface temperature of May in north Pacific as well as in equatorial east Pacific. When the SST of May is high in north Pacific and low in east Pacific,it rains more in summer.On the contrary ,it rains less.The SVD analysis shows the same result.Compositive 500hpa height fields in May of wet summer years differs a lot from dry ones. When it is "-,+"pattern from west to east in Asia which means the Ural high and the east asia trough are both weaker than normal,it rains more. It is also proved that a higher SST in May of north Pacific is followed by more rainfall in summer.The singular value decomposition(SVD)technique is used again when we try to find the relationship between 500hpa height field and the SST field in northern Pacific. One result shows that the 500hpa geopotential field in eastern Asia of April and May affected the SST field in northern Pacific of May;The other indicates that the northern Pacific SST field in May has effect on the 500hpa geopotential field in July of subtropical area where the western Pacific subtropical high usually stays then.Thus the reason of a good relationship exists between SST in northern Pacific and summer precipitation in Shandong Province can be explained as following:inthe wet summer years, longitude circulations prevail in May and SST in northern Pacific is higher which leads the subtropical high to a position of north and west to nomal. As a result,the wet and warm air current can arrive at Shandong where it is converged by cold current. Then it rains more. The situation is reverse on the contrary. From the analysis above, we can use SST of northern Pacific in May as a factor to foretell the summer precipitation in Shandong province,especially in Qingdao,Rizhao and Linyi region.