亚洲急流与冬季风的关系及其对中国气候的影响

The relationship between Asian,jets and the winter monsoon and their impact on climate in China

中文关键词:  副热带急流  温带急流  东亚季风  高原季风  中国冬季气候

英文关键词:Subtropical jet  Temperate jet  East Asian monsoon  Plateau monsoon  Winter climate in China

中文摘要:

      利用NCEP\NCAR逐月再分析资料和中国台站逐日观测数据,采用奇异值分解(SVD)、相关分析和合成分析等方法,研究冬季亚洲高空急流的配置与冬季风的关系及其对地面气候的影响.结果表明,青藏高原至亚洲东部沿海的副热带急流强(弱),高纬的温带急流弱(强)时,中国中、东部大范围地区气温偏低(高);中东急流强(弱),东亚副热带急流偏南(北),温带急流东南部较弱(强)时,西南气温偏低(高),东北气温偏高(低),中、东部地区冬季降水偏多(少).结合水平风场的变化,副热带地区出现西风异常弱,温带出现东风异常时,有利于东亚大槽加深并向南扩张,低层偏北风加强,东亚冬季风增强,而青藏高原反气旋环流被削弱,冷高压减弱,相应的高原季风减弱.高、低纬急流区纬向风的差异较大时,加强了急流对低层冷、暖空气交绥的引导和汇聚的作用.东亚季风指数(EAMI)与高原季风指数(PMI)在冬季多呈负相关.冬季风异常期间,若副热带急流偏强,温带急流偏弱,高纬的干冷空气受南侧急流的汇聚作用而南侵,有利于中国大部分地区降温,降水减少;反之,低纬的暖湿气流受到北侧急流引导而向北输送,导致中国大部分地区升温,降水偏多.

英文摘要:

      Based on the NCEP/NCAR monthly rcanalysis data and daily observed data of the 542 stations in China, by using the singular value decomposition(SVD),correlation analysis and composite methods,the relationship between the configuration of upper-tropospheric jet activity and the winter monsoon as well as their impact on the distribution of winter temperature and precipitation in China are investigated.It is indicated that when the intensity of the subtropical jet from the Tibetan Plateau to the eastern coast of China is increased (decreased),and the temperate jet in the middle-high latitudes is decreased (increased), temperatures in the greater part of China tend to be lower(higher).If the intensity of the Middle East jet is increased (decreased),East Asian subtropical jets move towards south(north)and the southeastern part of the temperate jet is weak(strong),temperatures in southwestern China are lower(higher) while those in northeastern China are higher(lower),andthere is more (less) precipitation in eastern China.Associated with the variation of the horizontal wind components, the westerly anomaly over the subtropical regions and easterly one over the temperate regions strengthen the East Asian trough and weaken the high pressure on the Tibetan Plateau,leading to a stronger East Asian monsoon and a weaker Plateau monsoon,as well as cold air in high latitude moving toward south.hhe velocity gradient of tonal wind between the subtropical belt and the temperate zone appear to reinforce the confluence of cold air with warm air at low levels.The correlation matrix shows that the East Asian monsoon index(EAMI) and the Plateau monsoon index(PMI) have significant negative correlation in winter to each other.During a period with abnormal winter monsoon,if intensity of the subtropical jet is strong and the temperate jet is weak, the cold air would be sucked to South China, leading to reduce temperatures and less rainfalls in China.Conversely, the warm air would be sucked to North China, then temperatures rise and there tend to cause more precipitation in China.