Characteristics and Causes of Low-level Wind Shear's Evolution over the Eastern Part of Northwest China during 1953-2012
In this paper,the global reanalysis wind data and the mean monthly reanalysis data of NCEP/NCAR in 1953 2012 are used to analyze the characteristics and causes of low-level wind shear's evolution over the east part of Northwest China,with the method of correlation analysis,variation rate analysis,and Mann-Kendall test and wavelet analysis.Results show that the annual low-level cyclonic wind shear frequency decreased significantly in the 60 years,and there was an abrupt change point in 1976.The wind field convergence decreased significantly and the convergence condition which may induce precipitation appeared less in the recent 30 years in the east part of Northwest China.There is 3 7 year oscillation periods in 1960 1970,and the 3 year and 7 year periods were the most remarkable.It basically coincided to the period ofthe precipitation in Northwestern China in time and space.The main reason of the low-level cyclonic wind field evolution was the significant adjustment of atmospheric circulation in the same period.
NETL
NSTL
万方数据
