Analysis On Characters And Causes Of Summer High-temperature Anomaly In Shandong Province

Base on the NCEP/NCAR reanalysis monthly mean data and the data of summer high-temperature in 80 meteorological observation stations in Shandong province from 1951 to 2002, spatial and temporal characteristics of summer high-temperature are analyzed, and the relations between the atmospheric circulation and high-temperature patterns , and those between Pacific sea surface temperature and summer high-temperature are discussed. The factors and "key regions" which have important influence on summer high-temperature in Shandong are discovered.There are more summer hot days in the inland of Shandong than in coastland, and more in plain than in mountainous area. The hot days occur in June and July in most Shandong inland, and often occur in July in the area of Shandong peninsula and coastland. The hot days which reach above 40 degrees centigrade mostly emerge in the western part of Shandong, and usually emerge in June.The high-temperature data from 80 gauge stations in Shandong are analyzed by means of EOF and REOF. The results indicate that there are three main patterns for the summer high-temperature. The first pattern is synchronized in all area of Shandong province, the second is out of phase with northwestern part and southeastern part, and the third is out of phase with northeastern part and southwestern part. The high-temperature anomaly mainly occurs in the northwest area, southwest area, southeast area and the inland of Shandong peninsula.There was apparent annual and decadal variation for summer hot days in Shandong. The annual number of hot summer was highest during 1950's and 1960's, and began to drop at the end of 1960's, after arriving the lowest in 1980's, then increased from 1990's to the early of 21 century. In recently more than 50 years, there was a course of down to up climatic change for the summer hot days, and an evident transition from more to less, strong to weak had happened about at the end of 1960's.The relation between the atmospheric circulation and high-temperature patterns during summer in Shandong province is discussed. The results indicate that the composite of the atmospheric circulation in hot summer is very different from that in cool summer. In hot summer, Mongolia warm-core low is stronger, and the western Pacific subtropical high is weaker and its location is usually to the north and east, while it is reverse in cool summer. Latitude circulations exist in the fields of 500hPa height in hot summers and longitude circulations exist in cool summers. In spring before cool summer, the trough in east Asia is deeper and Mongolia high is stronger, while it is reverse in spring before hot summer.The relationship between 500hPa height fields and summer high-temperature in Shandong province is studied by using the correlative coefficient analysis and thesingular value decomposition (SVD) technique. The results show that there is apparent negative correlation between summer high-temperature in Shandong and the geopotential height of 500hPa over Ural area, the area from the Caspian Sea to the Persian Gulf and over the subtropical west Pacific, and these regions are "key regions". In the preceding spring, the deeper trough in Eurasia and the distinctly lowered geopotential height of Ural area and the weaker western Pacific subtropical high are the main causes of numbers of hot days during summer, and the flatter trough in Eurasia and the distinctly higher geopotential height of Ural area and the stronger western Pacific subtropical high are the main causes of few hot days during summer, hence it can be factors through which to forecast the summer hot days in Shandong province.The relations between extreme high-temperature and the sea surface temperature in the eastern equatorial Pacific are studied, there is apparent negative correlation between the summer extreme high-temperature of Shandong and the preceding monthly sea surface temperature of the eastern equatorial Pacific, especially in March last year.The relationship between the Pacific sea surface temperature (SST) and summer...