Intra-seasonal Features of an Extreme High Temperature Event in 2011 in Eastern China and Its Atmospheric Circulation |
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| Authors: | GAO Qing-jiu LI Yan and HAN Tong-xin |
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| Institution: | Key Laboratory of Meteorological Disaster, Ministry of Education (KLME), Joint International Research Laboratory of Climate and Environment Change (ILCEC), and Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science and Technology, Nanjing 210044 China |
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| Abstract: | Based on the daily maximum air temperature data from the China Meteorological Data Network and the NCEP/DOE reanalysis data, the intra-seasonal circulation and evolution of an extreme high temperature event (EHTE) in the middle reaches of the Yangtze River (MYR) from August 9-21, 2011 were explored, as well as the influence of diabatic heating on the position variation of the Western Pacific subtropical high (WPSH). Results show that the daily Tmax in the MYR exhibits a vigorous intraseasonal oscillation (ISO) of 10-25 days in the extended summer of 1980-2018. The main factors affecting the EHTE in the summer of 2011 are the low-frequency wave train propagating southeastward in the mid-latitude of the upper troposphere and the low-frequency anticyclone moving northwestward in the low- latitude of the mid-lower troposphere. The diagnosis of 925hPa thermodynamic equation indicates that the ISO features of the Tmax in the core region is determined by the intra-seasonal variation of the adiabatic variation. In addition, the variations of the WPSH correspond well to the distribution of apparent heat source. In the early stage of the high temperature process, the apparent heat source in the north of the Bay of Bengal is a certain indicator for the westward extension of the WPSH. |
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| Keywords: | extreme high temperature event intra-seasonal oscillation diagnosis Western Pacific subtropical high complete form of vertical vorticity tendency equation |
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