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2017年秋季华西秋雨的多时间尺度变化特征及成因分析
(1.上海市气候中心;2.国家气候中心)
Characteristics of variability on multiple timescales and cause analysis of autumn rainfall in Western China during 2017
(1.Shanghai Climate Center;2.National Climate Center)
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投稿时间:2018-04-08    修订日期:2018-09-18
中文摘要: 利用我国723个常规观测气象站降水资料和NCEP再分析资料等,综合大气环流的季节内-季节异常、海洋外强迫年际异常及降水的长期变化影响,分析了2017年华西秋雨异常的成因。结果表明:20世纪60年代以来,华西秋雨存在3-4年、6-9年、12-18年、36年等多个时间尺度的准周期变化,并自1990年以来呈现增加的长期变化趋势。2017年华西秋雨异常偏多是多时间尺度变率叠加影响的结果。2017年秋季,北半球极涡偏向东亚地区,贝加尔湖低槽多冷空气分裂南下,西太平洋副热带高压异常偏强偏西,华西地区处于水汽输送异常辐合大值区,出现降水异常偏多。在季节内时间尺度上,东亚夏季风的季节内撤退过程偏慢,夏季风北界位置持续偏北,9-10月主雨带维持在华西-江汉-江淮一带。自西太平洋经南海北上的水汽输送的季节内变化,并与东北冷涡的季节内活动相配合,是造成华西秋汛的季节内环流影响因子。华西秋雨年际异常与赤道中东太平洋海温呈现显著的负相关。夏末秋初开始发展的拉尼娜状态是2017年我国秋季降水异常的重要外强迫因子。2017年华西秋雨的异常偏多也与其近年来的年代-多年代际正距平位相及长期增加趋势相联系。
Abstract:Based on the precipitation observations from 723 basic meteorological stations in China and the NCEP reanalysis data, the possible causes of the 2017 autumn rainfall anomalies in West China are investigated by detailed investigations about the impacts of sub-seasonal to seasonal anomaly of atmospheric circulation, inter-annual anomaly of external forcing from ocean together with long-term variations of precipitation. Results show quasi-period variations with multiple timescales, including 3-4a, 6-9a, 12-18a and 36a since 1960s, along with an increasing long-term trend since 1990 are found in the changes of autumn rainfall in Western China. The abnormally heavy rainfall in West China during autumn of 2017 results from the superposition influences from multi-time scales variations. In the autumn of 2017, the position of polar vortex in the northern hemisphere was derived towards East Asia, allowing the cold air from the low trough near Lake Baikal to spill southward. Meanwhile, the West Pacific Subtropical High was excessively stronger and westward. Therefore, a stronger water vapor convergence area was formed and eventually led to the abnormally heavy rainfall in Western China. On sub-seasonal time scales, the East Asian summer monsoon retreated more slowly than normal, and the northern boundary position of the summer monsoon was continuously maintained northward than normal. The main rain band was correspondingly maintained around the region of Western China, Jianghuai and Hanjiang in September and October. The sub-seasonal variations of the northward water vapor transportation from the West Pacific Ocean through the South China Sea, together with the sub-seasonal activities of Northeastern Cold Vortex, may be sub-seasonal circulation factors which influence the autumn rainfall anomaly in Western China. In addition, the inter-annual anomaly of autumn rainfall in Western China and central-eastern equatorial Pacific SST shows a remarkable negative correlationship. The La Nina condition developed from the late summer and early autumn in 2017 acts as the important inter-annual forcing of autumn rainfall anomalies. Also, the abnormal heavy rainfall in Western China is related to positive phases of decadal to multi-decadal variability and long-term increasing trend in recent years.
文章编号:201804080157     中图分类号:    文献标志码:
基金项目:国家重点研发计划“重大自然灾害监测预警与防范”专项(2017YFC1502301);国家自然科学基金项目(41775047);公益性气象行业专项(GYHY201406001);国家气象科技创新工程“次季节至季节气候预测和气候系统模式”
引用文本:
梁萍,周兵,马悦,汪佳伟,0.[en_title][J].Meteor Mon,():-.
Liang Ping,Zhou Bin,Ma Yue,Wang Jiawei,0.Characteristics of variability on multiple timescales and cause analysis of autumn rainfall in Western China during 2017[J].Meteor Mon,():-.