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气象:2021,47(1):117-126
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2020年夏季我国气候异常特征及成因分析
刘芸芸,王永光,柯宗建
(国家气候中心,中国气象局气候研究开放实验室,北京 100081; 南京信息工程大学气象灾害预报预警与评估协同创新中心,南京 210044)
Characteristics and Possible Causes for the Climate Anomalies over China in Summer 2020
LIU Yunyun,WANG Yongguang,KE Zongjian
(Laboratory for Climate Studies, National Climate Centre, CMA, Beijing 100081; Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044)
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投稿时间:2020-10-14    修订日期:2020-12-14
中文摘要: 2020年夏季我国天气气候极为异常,全国平均降水量为373.0 mm,较常年同期偏多14.7%,为1961年以来次多;季节内阶段性特征显著,6—7月多雨带主要位于江南大部—江淮地区,8月则主要在东北、华北及西南地区,致使2020年夏季雨型分布异常,不是传统认识上的四类雨型分布。通过对同期大气环流和热带海温等异常特征分析发现,6—7月,欧亚中高纬环流表现为“两脊一槽”型,东亚副热带夏季风异常偏弱,西太平洋副热带高压(以下简称西太副高)较常年同期显著偏强、偏西,第一次季节性北跳偏早,第二次北跳明显偏晚,且表现出明显的准双周振荡特征;使得来自西北太平洋的转向水汽输送偏强,并与中高纬不断南下的冷空气活动相配合,水汽通量异常辐合区主要位于长江中下游地区,导致江淮梅雨异常偏多。热带印度洋持续偏暖对维持6—7月西太副高偏强偏西及东亚夏季风异常偏弱起到了重要作用。8月,欧亚中高纬环流调整为“两槽一脊”型,蒙古低压活跃;西太副高也由前期偏纬向型的带状分布转为“块状”分布,脊线位置偏北;沿西太副高外围的异常西南风水汽输送延伸至华北—东北南部,形成自西南到东北的异常多雨带,与6—7月江淮流域降水异常偏多的空间分布有明显不同。异常的热带大气季节内振荡活动是导致8月中低纬大气环流发生调整的重要原因。
Abstract:In the summer of 2020, the weather and climate in China were extremely abnormal. The national average precipitation was 373.0 mm, with 14.7% more than normal, which is the second most since 1961. The intraseasonal variation of summer rainfall was obvious. The rainbelt from June to July was mainly located in the Yangtze-Huaihe River Valley (YHRV), but moved northward to Northeast China, North China, and Southwest China in August, making the distribution of summer rainfall in 2020 not belong to any of the four traditional patterns of rainfall. The observational analysis on atmospheric circulation and sea surface temperature indicates that the atmospheric circulation in the mid-high latitude was characterized by “two ridges and one trough” over Eurasia from June to July. The East Asian summer monsoon (EASM) was very weak, and the western Pacific subtropical high (WPSH) was much stronger and further westward than normal. The meridional movement of WPSH presented the characteristics of quasi-biweekly oscillation, accompanied with the early first northward jump and delayed second northward jump, which makes the intensified water vapor transport from the tropical Northwest Pacific. Combined with the cold air activities going southward from the mid-high latitude, the abnormal moisture convergence was located over the middle and lower reaches of the Yangtze River, which leads to excessive Meiyu rainfall in YHRV. The persistent Indian Ocean basin-wide warming played an important role in maintaining the stronger WPSH and weaker EASM than normal during June-July. By contrast, the atmospheric circulation in mid-high latitude was adjusted to “two troughs and one ridge” over Eurasia in August, with a low trough near Mongolia; the WPSH changed from the East-West zonal distribution to the “block” pattern, located further northward. The abnormal southwesterly moisture transport along the edge of WPSH extended to North-Northeast China, forming an abnormal “northeast-southwest” rainbelt, which is obviously different from that during June-July. The abnormal activity of the tropical Madden-Julian Oscillation was an important factor for the adjustment of the atmospheric circulation in mid-low latitude in August 2020.
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基金项目:国家重点研发计划(2018YFC1505806)、中国气象局创新发展专项(CXFZ2021Z033)和中国气象局预报员专项(CMAYBY2020-164)共同资助
引用文本:
刘芸芸,王永光,柯宗建,2021.2020年夏季我国气候异常特征及成因分析[J].气象,47(1):117-126.
LIU Yunyun,WANG Yongguang,KE Zongjian,2021.Characteristics and Possible Causes for the Climate Anomalies over China in Summer 2020[J].Meteor Mon,47(1):117-126.