中高纬瞬变涡旋活动对我国东部夏季降水的影响

基于1981—2020年日本气象厅(Japanese Meteorological Agency,JMA)再分析资料JRA-55(Japanese 55-year Reanalysis)以及美国国家气候中心(Climate Prediction Center,CPC)卫星降水资料,分析了瞬变涡旋活动特征及其对我国东部夏季降水异常的影响,并对其可能机制展开讨论。研究表明,蒙古国至我国东北和华北地区既是瞬变涡旋活动的活跃区域,也是其输送的大值区域,其中瞬变涡旋对热量和水汽的经向输送占主导地位,是中高纬热量和水汽的重要来源。根据瞬变涡旋经向热量和水汽输送变率的强度确定了瞬变热量和水汽输送的关键区域,分别为(45°~60°N,100°~130°E)和(35°~50°N,100°~120°E),并定义了瞬变热量和水汽指数,其与我国东部夏季降水异常的回归结果表明,瞬变涡旋活动对我国东部夏季降水存在显著影响。中高纬天气尺度瞬变涡旋对热量、水汽和动量的输送异常,通过波流相互作用过程,对平均流形成了反馈,导致季节平均环流、水汽分布和水汽输送的异常,从而在热力、动力和水汽条件的共同作用下引起降水异常。

The influence of middle-to-high latitude transient eddies on summer precipitation anomalies in eastern China

Based on the reanalysis data JRA-55 (Japanese 55-year Reanalysis) of the Japanese Meteorological Agency (JMA) and the satellite precipitation data of the Climate Prediction Center (CPC) in the United States from 1981 to 2020, the characteristics of transient eddies and their effects on the summer precipitation anomalies in eastern China were analyzed, and the possible mechanisms for these effects were discussed. Results show that the region from Mongolia to Northeast and North China is not only an active region of transient eddies, but also a large value region of transient eddy transport. The meridional transport of heat and moisture that plays a dominant role in the transient eddy transport process, is an important source of heat and moisture in middle-to-high latitude. According to the intensity of the heat and moisture transport variability of the transient eddies, the key regions of the transient heat and moisture transport were identified as (45°-60°N,100°-130°E) and (35°-50°N,100°-120°E), respectively, and the transient heat and moisture indices were defined. The regression results with the summer precipitation anomalies in eastern China show that the transient eddy activities have significant effects on the summer precipitation in eastern China. The anomalies of transport of heat, moisture and momentum by the middle-to-high latitude synoptic scale transient eddies has formed a feedback to the mean flow through the wave-flow interaction process, resulting in anomalies of seasonal mean circulation, moisture distribution and moisture transport, and thus causing precipitation anomalies under the combined influence of thermal, dynamic and moisture conditions.