| The in situ temperature data from 1961 through to 2004 and monthly mean anddaily data from NCEP/NCAR Reanalysis have been used to analyze not only thetemporal and spatial variation but also dynamic and thermodymanic mechanics ofhot summers in East China. The results are summarized as follows:(1) The colding trend of the summer temperature has been observed. Three criterions fordefining the hot summers have been set up, with which 10 hot summers have been clarified from1961 to 2004. The summer mean temperature field in East China can be divided into threesubdivisions. The analysis of the climatic catastrophic features as well as periodicities for eachsubdivision suggests that there are no significant temperature changes in these subdivisions butnorthern subdivision. The periods of both 2a and 3-4a are found to prevail in any one of the threesubdivisions. Anomalous hot summers occur frequently from the 1990s.(2) Influences of the subtropical high over the Northwest Pacific on theoccurrence of hot summers in East China are significant. The differences intemperature changes are distinguished among subregions in East China because ofthe movement of the subtropical high. When North China, the southern part of theNortheast China and Japan are anomalously controlled by the subtropical high, thetemperature in northern subdivision will be high. The temperature changes in middleand southern subregions are similar as compared to those in northern subdivisions.(3) The hot summers in each one of three subregions in East China is caused bythe dynamic heating as indicated by the vertical advection of temperature. Thehorizontal advection of temperature plays a less important role in inducing hotsummers in comparison with the diabatic factor and the vertical advection oftemperature. (4) Significant positive correlations have been found between the summer meantemperature in East China and SSTA of each month: from July to December informer year, in the Key region [180°E～100°W, 10°S～10°N]. This result is veryimportant to climate predictions.(5) In 1994, the abnormally blocking pattern near middle-high latitude is notconstantly there as usual. The ITCZ in low latitude is strong, while the ridge line ofsubtropical high moves northward. Height field at 100hPa shows a typical IranianHigh pattern. In the northern subdivision, diabatic heating plays an important role inhot summer in 1994. Whereas in the middle subdivision, vertical advection oftemperature named the dynamic heating dominates the heating rate. However, theeffect of horizontal advection in the southern part is weak. In both 1998 and 2003,blocking circulation is observed in middle-high latitude. The ITCZ is weak and theposition of subtropical high is more northern than normal. In 1998, the South AsianHigh has a signature of the "East" type over Tibetan Plateau. In 2003, two centers ofSouth Asian High are observed: the one on Iranian Plateau is broader in area and isstronger in strength. The meridional winds display that Rossby wave energydisperses eastward causing the anomalous anticyclone intensifying periodically in theupper troposphere and henceforth inducing hot summers in the middle and northernparts of East China.
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