摘要:梅雨降水具有显著的阶段变化特征，研究持续强降水期间的关键环流稳定分量，对于分析和预测梅雨降水具有重要意义。利用NCEP-DOE1979～2016年逐日再分析资料，对2016年梅雨持续强降水期间位势高度场、风场和相对湿度场进行分析，提取环流系统的关键稳定分量，并对其空间结构、演变特征及更长时间尺度的背景形势进行分析，为梅雨区阶段性强降水的延伸期预报提供依据和参考。研究发现：（1）在位势高度场稳定分量中存在的“三极”分布形势，是维持2016年梅雨持续强降水的关键系统。“三极”分别对应着乌拉尔山阻塞高压、鄂霍茨克海阻塞高压以及偏东偏强的南亚高压和偏西偏强的西太平洋副热带高压（副高）。这种配置结构有利于冷暖空气在梅雨区交汇形成持续性强降水。（2）在中高纬度两个正距平区之间，是相对深厚的负距平区，有利于建立冷空气的向南输送通道，同时相对湿度场稳定分量表明北支气流对水汽的输送和汇聚作用对于梅雨区持续降水起到重要作用。（3）中低纬度的正距平区域呈纬向带状分布，且主要存在于对流层中高层，在梅雨区东西两侧各有一个正距平下沉支，它们共同加强了梅雨区南侧暖湿气流的汇聚输送作用。（4）通过对稳定分量的演变分析发现，“三极”系统的建立和演化与梅雨区降水强弱的阶段变化密切相关。（5）更长时间尺度（60 d）环流稳定分量为持续强降水时段的“三极”关键稳定分量提供了重要的环流背景。
关键词:梅雨/
稳定分量/
空间结构/
演变特征
Abstract:There are significant precipitation stages that bring changes during the rainy period known as Meiyu. It is important to study the key stable circulation components that lead to the continuous heavy rainfall of this period to enable the analysis and prediction of Meiyu precipitation. Using NCEP/DOE Reanalysis II data from 1979 to 2016, the key stable components of the circulation system during the 2016 Meiyu period were extracted from the geopotential height field, wind field, and relative humidity field. The spatial structure, evolutionary characteristics, and longer-term background factors were analyzed to provide a basis for extended period forecasts of the periodic heavy rainfall in the Meiyu area. The results suggest that (1) the “tri-pole” pattern is the key system that maintained the continuous heavy rainfall in the Meiyu area in 2016. This “tri-pole” pattern in the stable components of the geopotential height field corresponds to the Ural Mountains blocking high, the Okhotsk Sea blocking high, the Southeast Asia high, and the West Pacific subtropical high. The structure of this configuration is conducive to the convergence of warm and cold air in the Meiyu area to generate persistent heavy rainfall. (2) In the middle and high latitudes, there is a relatively deep negative anomaly between two deep positive-anomaly areas. On one hand, this is conducive to the southward transport of cold air. On the other hand, the stability of the relative humidity field indicates that the water vapor transport and convergence of the northern branch of the air flow play an important role in the continuous precipitation of the Meiyu area. (3) The positive-anomaly area in the middle and low latitudes mainly occurs in the middle and high troposphere with zonal distribution features. However, there are two positive areas on both the eastern and western sides of the Meiyu area, which continue down to the lower level and may strengthen the convergence and transport of warm and humid air in the south of the Meiyu area. (4) The analysis of the evolution of the stable component revealed that the establishment and evolution of the “tri-pole” pattern led to different precipitation-stage characteristics in the Meiyu area. (5) The stable circulation components on a longer time scale (60 d) provide important background circulation for the key stable components of the “tri-pole” pattern during the period of continuous heavy rainfall.
Key words:Meiyu/
Stable components/
Spatial structure/
Evolution characteristics
注释:
1) 中国气象局预报与网络司. 2014. 关于印发《梅雨监测业务规定》的通知, 气预函（2014）28号 [R].
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