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

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.