南支槽对广西地区春末夏初降水的影响分析

The Impact Analysis of Southern Branch Trough to the Late Spring and Early Summer Precipitation in Guangxi

为研究春末夏初时期南支槽对下游广西地区降水的影响情况,本文采用NCEP/NCAR Reanalysis 1提供的资料,通过定义南支槽强度指数、标准化方法划分南支槽强弱年、做出5月南支槽强度指数与广西地区春末夏初降水的相关分析以及对比分析强弱年的背景场,结果表明:1) 近41年南支槽整体强度出现逐渐减弱的趋势,弱南支槽有6年,有9年表现为强南支槽特征。2) 广西地区降水与南支槽强度指数相关性较强,相关度是从桂西往东递减的趋势。3) 强弱年槽前西南气流来源不一,与南亚高压的配合,对广西地区降水也有较大的影响。4) 强年的槽前上升运动较为强烈,弱年的表现较弱,甚至出现下沉运动,且地面往高层方向,上升速度递减率高于强年。5) 强年湿度大值区控制范围较弱年广,弱年里,广西地区只有西北部处于较大的比湿区。

In order to study the influence of the Southern Branch Trough on the precipitation in the down-stream Guangxi area in the late spring and early summer, this paper uses the data provided by NCEP/NCAR Reanalysis 1 to define the SBT Intensity Index, divide the strength years of the Southern Branch Trough by standardized methods, make correlation analysis between the SBT Intensity Index and the precipitation in late spring and early summer in Guangxi in May, and make comparative analysis of the background fields (low, medium and high level average circulation fields, vertical rising speed and specific humidity) of the strong and weak years. The results show that: 1) The overall strength of the Southern Branch Trough has gradually declined in the past 41 years. The weak Southern Branch Trough has 6 years and the Southern Branch Trough has 9 years of characteristics. 2) Precipitation in Guangxi region has strong correlation with the Southern Branch Trough intensity index and the correlation is decreasing from West to East. 3) The southwesterly airflow in front of the strong and weak year troughs has different sources, and the coordination with the South Asian High also has a greater impact on precipitation in Guangxi. 4) The upward movement in front of the strong year trough is relatively strong, while in weak year trough performance weak and even sinking movement occurs. At the same time, descending rate of the ascent rate is higher than that in strong years when the ground moves toward higher layers. 5) The control range of the high humidity area in the strong year is relatively wide in the weak year. In the weak year, only the northwest of Guangxi is in the larger specific humidity area.