西北地区感热异常特征及对降水的影响

Based on NCEP/NCAR and PRECL reanalysis data from 1971 to 2010, the characteristics and interrelation of sensible heat flux, precipitation and atmospheric circulation is analyzed in northwestern China during abnormal years of sensible heat flux. Conclusions are as follows: first mode of multi-year average sensible heat flux shows that consistent changes and second mode shows southeast to northwest antiphase changes. The sensible heat flux contributed the most in spring and summer during the abnormal years, accounting for 31.1% and 48.0%. Compared with normal years, the season in which the sensible heat flux changed the most was February and November in winter. Precipitation decreased from southeast to northwest, water vapor mainly came from westerly transportation. During years of high sensible heat flux ,subtropical high got weaker, with westerlies weaker ,making northwestern China dryer and less precipitation. Higher sensible heat flux in spring mainly contributed to the enhance of Siberian High, as well as weaker west wind component in northwestern China, beneficial to accumulate sensible heat flux.Higher sensible heat flux in spring in northwestern China, affecting subtropical high shifted eastward and weaker, making summer monsoon weaker, and the location of water vapor transformed from Indian Ocean was northward, making less precipitation in northwestern China. Years of lower sensible heat flux are on the contrary.