Effect Of Thermodynamic Process Over Tibetan Plateau On Low-frequency Oscillation Rainfall In Yangtze River Valley During Summer

Calculating the atmospheric heat source (AHS) database using NCEP/NCAR version I daily reanalysis data from 1971 to 2000 and the inverse calculation method and adopting the combined methods of correlation analysis and comparative analysis, the influence of the AHS over the Tibetan Plateau in summer on the large-scale AHS and the corresponding general circulation are studied and conclusions are drawn as follows:(1) AHS over the plateau in summer can trigger a heat source wavetrain propagating northeastward along the coast from the East Asian continent and West Pacific to Bering Strait-Arctic or even North America.(2) When AHS over the eastern plateau is intense (weak), the South Asian High will be in the east (west) and south (north) and the West Pacific subtropical highwill be in the west (east) and south (north). In terms of interannual variation, the South Asian High and West Pacific subtropical high have the relation that if the South Asian High and West Pacific subtropical high move on the same direction, they move together; if they move on the contrary direction, they part, for which AHS over the eastern plateau seems to be thermodynamically responsible.(3) Morlet wavelet analysis suggests AHS over eastern TP exists low-frequency Oscillation which major in 10-20 days from May to September, as well as the South Asian High and the West Pacific Subtropical high.(4) There exists a remarkable same term correlation between AHS over the southeastern TP and rainfall in Yangtze River Valley in summer. Besides, when the summer AHS over the eastern TP is stronger (weaker), not only 10-20 days but also 30-60 days low-frequency circulation, cycolnic (anticyclonic) circulation affect the Yangtze River valley, and the rainfall in that regionincreases (decreases). (5) AHS over eastern TP exists introseasonal oscillation not only in 1978 but also in 1999, and a remarkable correlation appears between AHS over eastern TP and rainfall in the Yangtze River valley at introseasonal oscillation period of time by cross spectrum analysis. In addition, the low-frequency anticyclonic and cyclonic affect alternately the region of Yangtze River valley during the low-frequency variarion of AHS over TP.