| By using the outgoing longwave radiation (OLR) data from the US National Oceanic and Atmospheric Administration (NOAA), ERA-interim reanalysis data from European Centre for Medium-Range Forecasting (ECMWF), precipitation data from Global Precipitation Climatology Centre (GPCC) and CMAP, as well as the daily observation data of 756 stations provided by China national Meteorological information Center.The convection characteristics and abnormal on Maritime Continent area(MC hereafter) in period of late fall and winter (November to next January) and late winter early spring(February-April) from 1979 to 2013 are analyzed. On this basis, the relationship between the Yunnan-Kweichow Plateau precipitation over the same period are analysed by constructing abnormal convective activity index. At the same time, the relationship between convective activity on MC region and the precipitation anomalies in southwest China which include Yunnan-Kweichow Plateau is analyzed by SVD. Get the following main conclusions:Convection activities over MC region from November to January concentrated on the southern hemisphere of the island of Sumatra, Borneo, sulawesi and New Guinea island, and the convective activity has a tendency to increase during the past 3 decades. MC region convection activities associated with the Yunnan-Kweichow plateau rainfall by local meridian circulation and atmospheric response to tropical heat forced Gill type mechanism. When the IOLR is positive (negative), i.e., the convections region are weaker (stronger) in MC, the precipitation is found to be less (more) than normal in the west of Yunnan-Kweichow plateau and simultaneously more (less) in the east. Circulation anomalies on Yunnan- Kweichow plateau isn’t only related to the vorticity source force caused by the divergent/ convergent movement over MC region, but also to wave action flux from the upper troposphere over the south side of plateau. The energy disperse to East and convergent in favor of maintaining the abnormal disturbances in upper troposphere.Similar to November to January, The strong convective centers mainly in the southern hemisphere of the island from February to April MC region, and gradually increasing during the past 3 decades. When IOLR high, namely MC weak convective activity area, the Mongolian high and the Aleutian low are abnormal north and eastward, cause the cold air range decreases, and the lower 700hpa low latitudes affected by anomalous anticyclonic circulation system in the north of the westerly, enhanced airflow produced a strong upward motion in the west side of the plateau, and combined low-level convergence, high-level divergence over the plateau,, coupled with the presence of the Yunnan-Kweichow plateau whole layer of strong water vapor transport, and water vapor is a strong convergence zone, resulting in rainfall in Yunnan-Guizhou Plateau more easily. Then the convective activity in MC region is typically stronger, the opposite situation.There are three maritime continent region of strong convection centers from June to October located in Indochina, Philippine island near the south and northwest of New Guinea, SVD analysis results in the southern Philippines island of New Guinea island and the north-west, MC OLR and the Southwest regional precipitation fields show that:when MC region OLR convective activity is low (high), the convective activity is stronger (weaker), the southern below normal precipitation in the Southwest (more), while the northern part of more precipitation (less). The anomalous vertical circulation between MC region and Yunnan- Kweichow plateau connects the updraft (downdraft) over MC region and downdraft (updraft) over the southern plateau. In addition, because of the wave energy generated by MC region convection anomalies and the energy from high latitudes spread downstream and convergent in central and east China together in the upper atmosphere conducive to the generation and maintenance of abnormal disturbances. |
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