Regional Climate Anomalies In The Maritime Continent During Boreal Summer:Phenomena And Mechanisms

The Marine Continent is closely related to the global climate varibility.In this dissertation,with the NCEP/NCAR and GPCP monthly reanalysis products,diagnostic analysis of characteristic precipitation variability in various regions of MC in the northern hemisphere summer(June--September)and their relationships with the tropical ocean signals,East Asian monsoon and China climate anomalies were conducted systematically.Results suggest as follows:(1)MC can be divided into four independent subregions based on precipitation variability.Precipitation anomaly in subregion I(central and eastern Indonesia region)is closed related to climate change and variability in the tropical Pacific;precipitation anomaly in subregion ?+?(ocean area in western Indonesia)is jointly influenced by the tropical Pacific and tropical Indian Ocean;precipitation anomalies in subregions ?(equatorial western Pacific area)and ?+?(eastern Philippines of the Pacific Warm Pool area)are influenced by monsoon activities in East Asia and convergence and divergence triggered by anomalies in the tropical ocean.(2)In the west part of the Maritime Continent,differences are found in precipitation between ocean area of west Java island(subregion ?)and the equatorial west Sumatran ocean area(subregion V)even they are closely related to each other.Abnormally high precipitation in subregion ? always corresponds to a convergent upwelling cyclone circulation in the lower troposphere in this district and its southwest area.When the signal of subregion V is removed,the IOD mode is showed in the Indian Ocean.Abnormally high precipitation in subregion V is accompanied by a similar circulation as it happens in subregion ?,but the range is smaller and shifted westward with the Asian summer monsoon decreased.(3)Big differences are found in precipitation between east Philippines Sea area(subregion ?)and the Pacific ocean area near the Northern Mariana Islands(subregion?)even they are closely related to each other.Precipitation in subregion ? is closely related to eastern Pacific type of ENSO and EAP/PJ wave patterns.Abnormally high precipitation in subregion ? always brings with weak East Asian summer monsoon.Precipitation in subregion ? has tight relationships with IOBM and South China Sea summer monsoon.Abnormally high precipitation in this area corresponds to a similar circulation as it happens in subregion IV but is shifted eastward,also the South China Sea summer monsoon is enhanced.(4)Indonesia can be considered as key area of the Maritime Continent(short for KMC).About 70%of the variance of the OLRA in KMC can be explained by ENSO signals.Abnormally high OLRA over the KMC triggers an EAP/PJ-like anomalous wave train that propagates northeastwards and leads to significant positive precipitation anomaly from the Yangtze River valley in China to the Islands of Japan.This EAP/PJ-like wave pattern becomes even clearer after the removal of the ENSO signal and the combined effects of ENSO and IOD,suggesting that convection anomalies over the KMC have important impacts on anomalous East Asian summer monsoon.(5)Significant interdecadal variations of diabatic forcing over key region of the Maritime Continent(KMC)can be found from 1979 to 2012.It intensifies before 1980s and peaks in the late 1980s and weakens after this period.It is found that surface latent heat flux and net long-wave radiation in the atmosphere are the dominant components.When the anomalies of diabatic heating are negative,in the meridional-vertical section averaged over[115°E-120° E],the well defined vertical circulation anomalies are observed with its ascent branches respectively over KMC and area near 30° N,and the descent branch over South China Sea.Water vapor transports from the bay of Bengal,South China Sea area to the east of China to benefit the positive precipitation anomalies.Results of the present study will be helpful for better understanding of the climate change mechanism over MC,and provide clues for fturther studies of the East Asian summer monsoon and abnormal climate variabilities in China.