EOF-based Analysis of Distribution and Environmental Field of Typhoon Rainstorms in Jiangxi
The present study aimed to develop a forecasting model for typhoon rainstorms to improve the accuracy of forecasts for such events.Based on rainfall data of 179 typhoon rainstorm events affecting Jiangxi between 1961 and 2019 and the European Centre for Medium-Range Weather Forecasts reanalysis data at a resolution of 0.125 °×0.125 °,we conducted empirical orthogonal function(EOF)classification and landing site classification analysis and identified five distribution types of typhoon rainstorms in Jiangxi.In all the cases,obvious jets were observed between typhoon circulation and the subtropical high.Spiral rainbands were present when typhoons entered Jiangxi.In addition to its correlation with typhoon path and intensity,the rainstorm area was predominantly influenced by upper-level divergence,low-level convergence in typhoon circulation,terrain,the westerly wind belt,and the southwest monsoon.The distribution types of these typhoon rainstorms include:(1)Provincial type.The north-central part of Jiangxi was under the influence of the South Asian high.Typhoons that landed in Fujian passed through Jiangxi's northwest on the west side of the subtropical high.The low-level jet stream and cyclonic shear around the typhoon circulation caused rainstorms and even heavy rainstorms.Typhoons that landed in Guangdong moved northward between two subtropical highs.Combined with the westerly wind belt,they caused large-scale heavy rainfall and long-distance rainstorms in Jiangxi.Typhoons that made landfall in Zhejiang headed westward on the south side of the subtropical high and entered the northern part of Jiangxi.Their spiral rainband caused widespread heavy rainfall.(2)Central-South type.With a convergence zone in the north of Jiangxi and a divergence zone in the south at the 200 hPa level,typhoons made landfall in Fujian and traveled westward through the central and southern parts of Jiangxi.The mid-level jet stream in the troposphere was located in the northern part of Jiangxi and it limited the development of the rainfall event to the north.Heavy rainfall events occurred in the front of the jet stream on the west/east side of the typhoons or in the cyclonic shear on the south side.When typhoons made landfall in Guangdong and moved eastward,the southeast jet stream on the east side,combined with terrain and westerly wind belt,caused heavy rainfall in the central and southern parts of Jiangxi.(3)Northeast type.When typhoons made landfall in Fujian and moved northward through northeastern Jiangxi,the low-level jet and cyclonic shear around the circulation were influenced by the southwest monsoon.Combined with high-level divergence,they caused heavy rainfall in northeast Jiangxi.Typhoons that made landfall in Zhejiang hovered westward within Anhui,and the spiral rainband caused heavy rainfall in northeastern Jiangxi.(4)Southeast type.At the 200 hPa level,a high-altitude trough moved eastward and affected Jiangxi.Typhoons made landfall in Fujian and moved northward from the west side of the subtropical high.The long axis of the typhoon shifted to a northeast-southwest direction,and the southerly jet stream on the east side of the circulation and cyclonic shear on the south side caused heavy rainfall in the southeastern part of Jiangxi.(5)Central type,where the typhoon made landfall in the northwest of Fujian and passed through the central part of Jiangxi.The mid-level jet stream in the troposphere was located in the northern part of Jiangxi.The convergence area on the south side of the typhoon,combined with the divergence area at 200 hPa,caused heavy rainfall in the central part of Jiangxi.
typhoonrainstormempirical orthogonal function(EOF)environmental field
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