A Study On The Influence Of The Qinghai-Tibet Plateau Heat On The Northern Marginal Area Of ??the Asian Summer Monsoon

Based on NCEP1 daily reanalysis data and GPCC precipitation reanalysis data during 1961 to 2016,thermal effects of Tibetan Plateau on the north marginal zone of Asian Summer Monsoon has been studied by the method of moving average,linear regression,composite analysis,power spectrum and Lanczos band-pass filter.The Monsoon Margin Index has been defined as a standard to divide the location of north marginal zone of Asian Summer Monsoon.The following three questions were discussed in this article that were the decadal variations of the location,precipitation,area of monsoon marginal zone and their relationships,the relationships between monsoon marginal zone anomalies and East Asia climate and the physical mechanism of the precipitation anomalies over monsoon marginal zone.The thermal effects of Tibetan Plateau on monsoon marginal zone has been discussed in the inter-annual and the intra-seasonal oscillation.The results show that:(1)The average position of monsoon marginal zone is a zonal region in the direction of southwest-northeast which is extending from the middle of Tibetan Plateau to Loess Plateau,Northeast China and the east coast of Asia.In this studies,three-members of the monsoon marginal zone has been adopted which were the West Member of Tibetan Plateau(85°~105°E),the Middle Member of Loess Plateau(105°~115°E)and the East Member of Northeast China(115°~135°E).The annual precipitation of monsoon marginal zone is from 450 mm to 500 mm.And,obvious decadal variability has been found through the position,precipitation and area of monsoon marginal zone.(2)The inter-annual of the precipitation of monsoon marginal zone associated with the water vapor transportation of Asian Monsoon Regions.And,the effects of water vapor transport associated with the anomaly of summer precipitation in Asian Monsoon region.(3)The abnormally less precipitation of monsoon marginal zone is related to the wave train of EU teleconnection pattern in middle-high latitude over Eurasia.The Somali Jet and Asian Monsoon were weaker than normal in the year with less summer precipitation over monsoon margin zone.At 200 hPa,the South Asia High was weaker and smaller.The Asian jet stream was also weaker and northward.At 500 hPa,the monsoon margin zone in the North China is characterized by the anticyclone center in the Mid-latitude westerlies.These are the physical factor of the abnormally less summer precipitation over monsoon margin zone.(4)The abnormally more precipitation of monsoon marginal zone is related to the wave train of Silk Road pattern in middle-high latitude over Eurasia.The velocity potential anomaly at 200 hPa was related to the more precipitation over Asian Monsoon Region in the year with more summer precipitation over monsoon margin zone.The South Asia High was stronger and bigger.At 500 hPa,the monsoon margin zone in the North China is characterized by the cyclone center in the Mid-latitude westerlies.These are the physical factor of the abnormally more summer precipitation over monsoon margin zone.(5)The statistical analysis of the heating effect of Tibetan Plateau and the inter-annual of monsoon margin zone shows that there exists an obvious correlation between them.The impact of the heating source in the west of Tibetan Plateau on the summer precipitation over monsoon margin zone is more significant(Key Region).The variability of Q1 in Key Region was mainly controlled by the BWO of 10~20 days in 2011,a typical year that the summer precipitation over monsoon margin zone was more than normal.The summer precipitation over monsoon margin zone and the northern Indian plain are in phase with the quasi-biweekly oscillation.When the BWO signal in its positive phase,monsoon margin zone members of Tibetan Plateau and Eastern China was characterized by the southerly winds of low-frequency cyclone system at 500 hPa.The member of Loess Plateau was characterized by the easterly winds of low-frequency anticyclone system at 500 hPa.The modulating effect of the low-frequency system on Asian Summer Monsoon Circulation which cause the precipitation of Asian Monsoon mainly focus on monsoon margin zone.The case is contrary in the negative phase of BWO signal.(6)The BWO signal of Q1 in Key Region can excite Rossby wave train over Eurasia mid-high latitude at 200 hPa.The range of the wave train was similar to the wave train of Silk Road pattern along the Asian jet stream.It is shown that a propagating eastward low-frequency radial wind wave may be induced on the west side of 90°E and the farthest distance can reach 120°E.But the low-frequency radial wind wave was dominated by the standing wave state in the range of 90°~120°E.The downstream propagation of the low-frequency radial wind wave in this range was difficult.The possible cause of the effect of Tibetan Plateau on the summer precipitation over monsoon margin zone was caused by the effect of Q1 in Key Region on the Rossby wave train of upper troposphere.