Combined Effects Of The MJO And The Arctic Oscillation Over Western And Central China Preciptation

In order to study the effects of Arctic Oscillation(AO)and Madden-Juilan Oscillation(MJO)on precipitation in central and western China,the ERA-Interim daily precipitation data from the European Medium Term Weather Forecasting Center(ECMWF)from 1979 to 2017 was used.The regression analysis and other methods were applied to study the relationship between atmospheric low-frequency teleconnection and precipitation in central and western China.The results show that:(1)AO has a significant impact on precipitation in the central and western regions of China,and the impact on daily average or monthly average precipitation is extremely significant.We selected the most significant correlation between AO and precipitation in January-March(Winter and Spring)for further analysis and found that when the AO activity in winter and spring is enhanced,it will drive the lower tropospheric water vapor in the western Pacific to the Bay of Bengal,and the Bay of Bengal.After the water vapor meeting,it entered the inland from southwestern China,causing an increase in precipitation in southwestern China and parts of the central region.At the same time,the westerly winds in the middle and high latitudes turned northward in the Balkan Lake area,resulting in areas such as Xinjiang in China that did not have sufficient water vapor supply in winter and spring,causing drought and little rain in northwestern China.When the AO activity is weakened,the situation is just the opposite.(2)MJO has a significant impact on precipitation in the central and western regions of China.The main areas of MJO's impact on precipitation are: the Qinghai-Tibet Plateau,the area near the Qiongzhou Strait,and the southern part of Xinjiang.Among them,the correlation between the Qinghai-Tibet Plateau is the most significant and lasts for the longest.The Qinghai-Tibet Plateau was selected as the main research area of the article.At the same time,the impact of MJO on the lag period precipitation in the central and western regions of China was examined,indicating that there is a significant lag in the impact of MJO on precipitation.This lag correlation was most pronounced in January.When MJO is located in Southeast Asia(Atlantic/Africa),the water vapor content of the Yunnan,Sichuan and Qinghai lines increases(decreases),and the vertical ascending motion increases(weaks),resulting in increased(decreased)precipitation in these areas;and the Qinghai-Tibet Plateau and China In the central part of the country,the water vapor is a net outflow(inflow),and the vertical ascending motion is weakened(enhanced),resulting in a decrease(increase)in precipitation in these areas.When MJO is located above the western Pacific Ocean(Indian Ocean),the vertical ascending motion in most parts of southern China is weakened(enhanced),and the net outflow(inflow)of water vapor causes a decrease(increase)in precipitation in southern China.(3)There is a certain interaction between AO and MJO on the impact of precipitation.When MJO is in different phases,the influence of AO changes on precipitation in the central and western regions of China is still significant,but there are significant regional and modal changes in different phases of MJO.It shows that AO and MJO have a certain modulation effect.