局地水汽异常引起的非绝热加热对2016/2017年中国南方暖冬的影响

EFFECT OF DIABATIC HEATING INDUCED BY REGIONAL WATER VAPOR ANOMALIES IN 2016/2017 WARM WINTER OVER THE SOUTH OF CHINA

基于NCEP/NCAR再分析资料,利用气温异常的倾向方程分析2016/2017年中国华北地区(100~115°E,35~45°N)、西南地区(85~102°E,22~33°N)和南方地区(108~118°E,22~33°N)的暖冬事件。结果表明西南和华北地区的平流作用占主导地位,而2016/2017年冬季中国南方暖冬主要是非绝热加热引起的。进一步通过水汽收支平衡的分析表明,局地水汽异常对2016/2017年中国南方暖冬有重要贡献,而其中土壤的水汽贡献约占50%。可能的机制如下:大气中正的水汽异常引起辐射加热增多,导致气温升高,土壤的感热增大,土壤温度升高,潜热通量变大,从而向大气的水汽输送增多,更多的水汽将导致更高的温度。

NCEP/NCAR reanalysis data are used to analyze a warm winter in 2016/2017 in three regions of China,i.e.,North(100~115°E,35~45°N),Southwest(85~102°E,22~33°N)and South(108~118°E,22~33°N),by analyzing the equation of air temperature budget.The results indicate that in the 2016/2017 warm winter event advection plays a main role over the north and southwest of China,but diabatic heating dominates over the south of China.Further analysis of moisture budget suggests that diabatic-heating-induced regional water vapor anomalies,about half of which come from soil,give great contribution to the 2016/2017 warm winter event over the south of China.A possible positive feedback mechanism is:positive water vapor anomalies increase radiation heat to warm the air,and then downward sensible heat flux increases soil temperature;as a result,larger upward latent heat flux leads to more water vapor,and then another cycle repeats.