Analysis On The Feature Of Moisture Flux Over Southwest China

Qinghai-Tibet Plateau is the top of key area of moisture transport "Large Triangle Region "in South Asian monsoon, which is at the upstream of the transferred station of moisture transport. And Southwest China is at the upstream of the transferred station of moisture flux. Southwest has been influenced by East Asian monsoon, South Asian and Plateau Asian. So studying moisture transport of Southwest China is very important for learning its climate anomalies and disaster prevention.and this study is contributive to reveal the relationship between the East Asian monsoon, the South Asian and the Plateau Asian. This analyzes the climate characteristic of moisture transport, the correlation of moisture transport and temporal and spatial distribution of precipitation, possible reason for moisture transport anomalies at the time of the summer drought and summer flood, the factors of affecting moisture transport anomalies on severe drought in the South Asian was discussed. And isotope data of satellite spectral is used to discuss the global distribution of vapor isotope and moisture transport over Southwest China.1. Through the systematic analysis of climate characteristics of moisture flux over Southwest China, the results are showed that atmospheric moisture content and net gain of moisture of Southwest is more in summer than in other seasons. the air moisture mainly concentrate under 500hPa in Southwest China; Sichuan Basin is one center of atmospheric moisture content of Southwest China and the moisture content of western Sichuan is very least; moisture content and moisture sources change with season movement.In spring, moisture sources mainly comes from the high latitude region. In summer, moisture is mainly from the Bay of Bengal. While in autumn, moisture mainly come from the Bay of Bengal, the westerly belt and the South China Sea area, while in winter primarily from the westerly wind belt; there is a strong moisture flux belt over Indian Ocean between the equator and 30°N, Pacific region. A strong zonal moisture flux belt exists at 700 -500hPa over China and the Pacifica, and a zonal belt at 500-300hap over high-altitude region of China land and the western Pacific; At the time of monsoon onset and withdraw or at time of before and after seasonal exchange, zonal moisture flux over Arabian Sea-India peninsula-Bengal bay-southern Indochina peninsula-South China Sea gradually strengthen (or weaken), and meridional moisture flux over Somalia strengthen (or weaken).2. How moisture transports affected on precipitation tempo-spatial feature of Southwest China was discussed. Based on analysis of the atmospheric moisture content, the net gain (or net loss) of moisture, moisture flux, the vertical moisture flux, how precipitation tempo-spatial characteristics of Southwest China formed are discussed. The study show that there is a good correspondence between moisture content,the net moisture gain or net moisture loss,moisture flux,the vertical moisture flux over the Southwest China and precipitation distribution of Southwest China.3. Moisture transport difference and its anomalies cause between during summer flood and during summer flood drought are analyzed. Moisture flux and its anomalies over the northern Bay of Bengal, northern Indochina Peninsula and over southern Indochina Peninsula are inverse, between during summer flood and summer drought. Wind fields anomalies at 850hPa,700hPa,500hPa over northern Bay of Bengal and over northern Indochina Peninsula region, Yunnan, Guizhou are different; sensible heat anomalies of Qinghai-Tibet Plateau take on an anti-phase feature from April to June during summer floods and during summer drought. At the same time, sea surface temperature anomalies are inverse between 30°S-10°S Indian Sea and Somali take on anti-phase features. The Arabian Sea and Bay of Bengal SST anomalies of are similar. The wind anomalies at 850hPa level of Northern Bay of Bengal and Indochina is different.4. The abnormal characteristics of water vapor transport in southwest in southwest 2009/2010 were analyzed, and its causes are discussed. Due to the reduction of meridional and zonal water vapor flux over Bay of Bengal decrease, which made net gain of warm moisture from Bay of Bengal decrease in Southwest China. September 2009 to April 2010; with West Pacific subtropical high more western and stronger and the westerly meridional circulation weakened, the interaction between cold stream and warm stream weakened over Southwest, which are disadvantage to format precipitation; the low-level flow of Bengal Bay and the South China Sea deflected, which makes the water vapor flux from above regions in the winter of 2009-2010; India-Burma Trough weakened and moved north, which makes the low-level flow field deflected March2010 and April 2010, which is disadvantage to water vapor transport from Bay of Bengal and the South China Sea to Eastern Yunnan, Guizhou and Sichuan Basin.5. Global atmospheric moistureδD distribution, its seasonal variation are analyzed, and writer analyzed the linkage of atmosphericδD change and temperature change and changes in humidity. The relation between the change of moisture flux over the Bay of Bengal and South China Sea and change of atmospheric moistureδD over Southwest China was preliminary analyzed.