【摘要】 利用1961-2010年川渝盆地气象站逐日降水量资料、NCEP/NCAR再分析资料,采用经验正交函数展开、多锥度—奇异值分解等方法,研究了川渝盆地夏季降水的季节内尺度、年际尺度和年代际尺度变化特征。结果表明:川渝盆地夏季降水主模态空间型为东西反向分布型。MTM-SVD分析指出,川渝盆地夏季降水的季节内变化主要表现为准33天振荡,典型循环体现了盆地东西反向分布和南北反向分布的交替演变过程;川渝盆地夏季降水的年际变化特征主要表现为准2年周期循环,并且准2年周期的空间异常分布与盆地夏季降水主模态一致,即东西反向分布;在年代际变化方面,1961-2010年盆地西部夏季降水为减少趋势,盆地东部为增多趋势;川渝盆地夏季降水在1979年和1987年前后出现过两次明显的突变;当南亚高压偏北偏东时,西太平洋副热带高压(下称副高)偏北,盆地东部在副高的控制下,盆地西部则处在副高西部边缘,来自孟加拉湾的暖湿空气被副高阻挡在盆西,导致盆地降水西多东少,而当南亚高压偏南偏西时,副高偏南,来自孟加拉湾的西南暖湿空气可以直接输送到盆地东部,盆地降水西少东多。更多还原

【Abstract】 In the past research,there are many studies on the characteristics of the summer precipitation in Sichuan-Chongqing basin,but most of them are separately discussed in terms of its annual or inter annual variation characteristics and its possible mechanism. The analysis of the characteristics of the seasonal variation is relatively less. Therefore,in this paper the characteristics of the seasonal interannual and decadal variation will be studied systematically and deeply from different time scales. The daily precipitation data from 1961 to 2010 of 24 meteorological stations are used in this paper. Use the same period monthly mean 500 h Pa,100 h Pa height field and1000 ~ 300 h Pa zonal wind and humidity field reanalysis data. Two methods are used in this article. MTM-SVD method is a multivariable frequency domain decomposition technique proposed by Park and Mann. The empirical orthogonal function expansion technique was introduced into the study of atmospheric science by Lorenz in the middle of 1950 s. The results show that the main mode of summer precipitation in Sichuan-Chongqing Basin is the East- west reverse distribution pattern. MTM- SVD analysis points out that the seasonal changes of summer rainfall at Sichuan-Chongqing Basin mainly reflected the oscillation of Quasi-33 day. The seasonal typical cycle performed the evolution between the distribution of east-west reverse and the north-south. Its interannual variation mainly showed Quasi-2 years cycle,which spatial distribution is consistent with that primary mode. In the aspects of decadal variations,the summer precipitation has decreasing trend in the western basin but growing trend in the eastern basin. The results of sliding t test indicated that the summer rainfall appeared two distinct mutations in 1979 and 1987. Synthetic analysis shows that corresponding to the abnormally northeastward South Asia high(SAH),the West Pacific subtropical high(WPSH)inclines to more northward,while the warm-humid air from the Bay of Bengal is blocked in the west basin which leading to more precipitation in west basin than the east basin. The southwestward SAH and the southward WPSH always accompanies more rainfall in the east basin than the west. In this paper,the fact of the multi scale variation of the precipitation in the basin is analyzed,and the general circulation background of the typical year is given too. The impact factors for different time scale characteristics are not the same. The characteristics of precipitation intraseasonal oscillation signal may affected by the plateau vortex and MJO. Interannual time scale signal is mainly affected by the Indian Ocean dipole,the thermal status of Tibetan Plateau external forcing,decadal scale change should be considering the factor of solar activities,etc.,which are worth further study.更多还原