Application Of MJO In The Prediction Of Summer Rainfall Extension Period In Tibet

In order to study the relationship between MJO and summer precipitation over the plateau,and find the precursory signals that can indicate the extended period forecast of summer precipitation over the plateau from MJO,In this paper,multi-source data,such as daily precipitation data,MJO monitoring products,daily multi-element reanalysis data and satellite inversion products,have been used for nearly 40 years.By means of band-pass filtering,EOF and synthetic analysis,the influence of MJO on Summer Precipitation over the plateau,the difference of summer precipitation over the plateau at different phases of MJO and the relationship mechanism between them are studied.Finally,a case diagnosis and model simulation are used to verify the results.The results show that MJO has a significant effect on the summer precipitation in the east of the plateau(TPE),especially on the precipitation near the southern water vapor transport channel.Further study on TPE delay precipitation probability in different phases of MJO shows that TPE precipitation probability increases exponentially from the 20 th day after the 4th phase of MJO(MJO?4th),and reaches the highest value at the 28 th day.This conclusion has been verified in two typical precipitation processes of Lhasa station in summer 2019,and the water vapor sources of these two precipitation fields point to the continental ocean area(the main convection area of MJO?4th).The results also show that whole East Indian Ocean-plateau-MC Region-East Asia and West Pacific Ocean is in a significant quasi 40 d low frequency oscillation after MJO?4th,TPE region is in a convective suppression region within 0-20 D,water vapor and convective disturbance are not conducive to transport to TPE,but this phenomenon is reversed from the twentieth day.Study on the relation mechanism between MJO?4th and TPE precipitation shows that the dynamic action shows that the pressure gradient force in the period of 0-20 days points to TPE from the MC area,and the effect of Coriolis force makes the former TPE to be an anticyclonic circulation,which is reversed from the 20 th day.The thermal effect shows that MJO releases latent heat to excite two cyclonic circulation systems on both sides of its diagonal after the MJO?4th,which make MJO have the components of Eastward Transmission and northward uplift respectively,and then through the early enhanced TPE sensible heat relay,the northward uplift MJO convective system is "pumped" over the plateau,resulting in TPE under the influence of both dynamic and thermal effects In the early stage of the MJO?4th,it is not conducive to precipitation,but the probability of precipitation is greatly increased from the 20 th day.Finally,after reducing the relative current intensity of MJO?4th by 8.15%,the precipitation of Lhasa station decreased by 68.89% after 20 days,which further verified the relationship between MJO?4th and TPE precipitation.The sensitivity tests of dynamic and thermal effects show that the effects of thermal effects on TPE precipitation are more important.