关键词: 华北地区, 低层风切变, 变化趋势, 影响因子

Abstract: Based on the monthly precipitation observation data at 21 weather stations in North China, global reanalysis data from NCEP/NCAR and circulation indexes data from National Climate Center of China from 1955 to 2014, the variation tendency, mutation and periodic characteristics of cyclonic wind shear frequency in low level in North China were analyzed by using the trend analysis, Mann-Kendall test and wavelet analysis methods, and the influence factors of cyclonic wind shear were preliminary discussed. Results show that the frequency of low-level cyclonic wind shear in North China decreased significantly during 1955-2014, the mutation of cyclonic wind shear frequency appeared in 1967, and there was quasi-3-year period oscillation during 1955-1965 and 1992-2000, while the 4-year period oscillation was significant during 1980-1992. The mutation and periods characteristics of low level cyclonic wind shear frequency were basically coincide with the precipitation in the same periods in North China. The turning change of low-level cyclonic wind shear was obvious in North China, which was mainly caused by the more significant adjustment of atmospheric circulation in the previous year.

Key words:  North China, low-level wind shear, variation tendency, impact factors