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Accueil du site → Doctorat → Chine → 2008 → Features of the Tibetan Plateau and Eastern Asia Atmospheric Heating LFO and Its Relations to Drought-Flood in Eastern China

Nanjing University of Information Engineering (2008)

Features of the Tibetan Plateau and Eastern Asia Atmospheric Heating LFO and Its Relations to Drought-Flood in Eastern China

Gong Yuan Fa

Titre : Features of the Tibetan Plateau and Eastern Asia Atmospheric Heating LFO and Its Relations to Drought-Flood in Eastern China

Auteur : Gong Yuan Fa

Grade : Doctoral Dissertation 2008

Université : Nanjing University of Information Engineering

Résumé
Based on the daily datasets from the National Center for Environment Prediction and National Center for Atmospheric Research(NCEP/NCAR)reanalysis(versionⅠ), Outgoing Longwave Radiation(OLR)data and the daily rainfall from the Chinese National Meteorological Information Centre,surrounding on the themes of the atmospheric heat sources()and their low frequency oscillation,the features of climatology,low frequency oscillation of over the Tibetan Plateau and Eastern Asia and their mechanism and relations to the subtropical high and the drought-flood of eastern China are clearly investigated by the synoptic-dynamical diagnosis.Main results are as follows :(1)The significant differences between the East Asian Monsoon System and South Asian(Indian)Monsoon System can be distinguished by the 30-70 days Oscillation(Intraseansonal Oscillation,ISO)and Bi-weekly Oscillation(BWO)of climatic .In the East Asian Monsoon area,there are two intensity oscillation belts of the ISO and BWO,the north oscillation belt is located to the subtropical latitude between the Yangtze River basin and the Pacific area of Southern Japan which is relation to the East Asian subtropical monsoon,the south oscillation belt is located to the tropical area between the South China Sea and the Ocean of the eastern Phillips which is relation to the tropical monsoon.In the South Asian(Indian) Monsoon area,the ISO is the most intensity oscillation over the Arabian Sea, side of the southwestern Tibetan Plateau and Bay of Bengal,but the intensity and area of the BWO are the weak and little.(2)In summer of the weak or strong East Asian monsoon,the over the Eastern Tibetan Plateau,the active or break rainfall of the Tibetan Plateau and the northward or southward shift of the subtropical high ridge have the same low frequency oscillation features.Their BWO are all very significance in summer of the weak monsoon,but the ISO are all more important in summer of the strong monsoon. Based on the correlation analysis,the variety over the Eastern Tibetan Plateau lead to the rainfall active or break on the Eastern Plateau,and then affected the northward or southward shift of the subtropical high.(3)For the typical great flood years and climate rainfall of the Yangtze River basin,the intensity of and OLR ISO is abruptly increasing from the ending of April to the beginning of May over the subtropical area of the northwest Pacific central section(near by 150°E,30°N).The strong ISO signal propagate westward to the Yangtze River basin of eastern China along 30°N during May and August,at one time,the ISO signal of the South China Sea propagate northward to the Yangtze and Huaihe River basin of China.The positive ISO(or the negative OLR-ISO)are converged over the Yangtze and Huaihe River basin in June and July,the location and time of the convergent area are maybe relations to the area and time of the "Meiyu" rainfall belt in summer.But the strong ISO signal is not obviously and westward propagation over the subtropical area of the northwest Pacific for the drought year of the Yangtze River basin,therefore it maybe be an another mechanism of the "Meiyu" rainfall that the strong ISO signal arises and propagate westward over the subtropical area of the northwest Pacific.(4)For the typical great flood years of the Yangtze River basin,the ISO anticyclone and cyclone system are continue making and move westward and northward to the eastern China and the coastwise western Pacific by the change of ISO during May and August.In the continuous strong rainfall period,on the 850hPa,a powerful ISO anticyclone system is formed from the South China Sea to the Pacific of south Japan,at one time,a strong ISO low-level jet stream belt is make from the China Jiangnan district to southern Japan Island and it is the convergence area from the Yangtze River basin to the Korea Island.On the 200hPa,it is an ISO anticyclone system centre over the Yangtze River basin and there is the ISO cyclone system convergence belt from the South China Sea to the ocean of eastern Taiwan. Owing to the ISO circulation system on the 850hPa and 200hPa,there are very steady ISO circulation conditions and moisture conditions which is beneficial to rainfall of the Yangtze River basin.

Mots clés : Tibetan Plateau Atmospheric heating 30-70 days Oscillation (ISO) Bi-weekly Oscillation (BWO)

Présentation (Dissertationtopic)

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