Forced Dissipative Nonlinear Critical Layer With Real Basic Flow And The Formation, Evolvement Of Subtropical High And Its' Impact On Precipitation In Yangtse-Huaihe River Valley

The paper is concerned for the nonlinear critical layer which is simulated by forced dissipative non-divergent barotropic vorticity equation with southern boundary stationary forcing. The cats'eyes obtained by replacing ideal basic flow with real wind fields in April of flooding and drought year in Yangtse-Huaihe River Valley is compared with real subtropical high in summer. Results show cats'eyes obtained by replacing basic flow with monthly-mean longitudinal wind fields in April of flooding year in yangtse-Huaihe River Valley is southern, western and stronger than the normal. While cats'eyes obtained by replacing basic flow with monthly-mean longitudinal wind fields in April of drought year in Yangtse-Huaihe River Valley is northern, eastern and weaker than the normal, which is accord with real subtropical high.By calculating the value of energy and quality latitudinal convergence in the nonlinear critical layer exprement, we conclude that quality latitudinal convergence center is at the north of the center of cats'eyes, but the evolution of both is almost the same. The greater energy basic flow transport to critical layer, the stronger the cats'eyes is, which is accord with the situation of real subtropical high. By calculating the value of real quality latitudinal convergence, we find that the convergence center is at the north of ridge line of real subtropical high, also the quality latitudinal convergence centre when subtropical high is southern than the normal is at the south of that when subtropical high is northern than the normal.We compositely analyse subtropical high over western Pacific Ocean anomalistic year which is stated by national climate center .Results show that when subtropical high is southern or western than the normal, blocking patter is active in middle and high latitude,the convergence is strengthening in the low and divergence is strengthening in the high in Yangtse-Huaihe River Valley ,the vertically ascending motion is strengthening in the middle definitely. In this situation, it easily rains in Yangtse-Huai River Valley. When subtropical high is northern or eastern than thenormal, it isn't benefitial to rain in Yangtse-Huaihe River Valley.The diagnostic analysis show the ridge line exponent in June and northern boundary exponent in July and August have the better correlation with precipitation in 160 stations in china. Correlation area is centered in Yangtse-Huaihe River Valley .We make singular value decomposition between 500hpa height fields which include west Pacific subtropical high and precipitation in 160 stations in china. From the first mode correlation map, we can conclude when subtropical high is southern than the normal, it rains more in Yangtse-Huaihe River Valley, which expains profoundly west Pacific subtropical high is critical to the precipitation in Yangtse-Huai River Valley. The variation of subtropical high over western Pacific Ocean during the floods in 1998 and 2003 is accord with the results in the numerical exprement above. Also analyse the characteristics of blocking high and jets in the low and in the high in 1998 and 2003.We come to the conclusion that energy and quality latitudinal convergence in the nonlinear critical layer make the cats'eyes form and evolve using southern boundary stationanry forcing, which is the new physical mechanism in the formation and evolution of subtropical high.Also we verify subtropical high over the Pacific Ocean have great impact on the precipitation in Yangtse-Huaihe River Valley.