2019年5月美国持续性降水异常影响因素分析  

Analysis of Influencing Factors of Persistent Precipitation Anomalies in the United States in May,2019

作　　者：杨晶 孙即霖 宁方悦[1] Yang Jing;Sun Jilin;Ning Fangyue(College of Oceanic and Atmospheric Science, Ocean University of China, Qingdao 266100, China;The Key Laboratory of Physical Oceanography, Ministry of Education, Ocean University of China, Qingdao 266100, China)

机构地区：[1]中国海洋大学海洋与大气学院,山东青岛266100 [2]中国海洋大学物理海洋教育部重点实验室,山东青岛266100

出　　处：《中国海洋大学学报（自然科学版）》2022年第7期22-29,共8页Periodical of Ocean University of China

基　　金：国家自然科学基金重点项目(41430963,41276012)资助。

摘　　要：利用NCEP/NCAR再分析资料、CPC降水数据等资料,对2019年5月美国出现的持续性强降水原因进行了分析。研究发现:(1)北半球不同纬度行星尺度波位相的配置构成了有利于持续性降水的环流形势:北极区呈现明显的一波结构,与45°N—60°N纬度带中异常偏强的2、3、4波结构相互叠加,造成持续时间较长的异常稳定环流形势,不同波数大气超长波和长波在阿拉斯加附近上空的叠加与偏暖的阿拉斯加湾海水的热力强迫一起,形成了振幅大、移动缓慢的高压脊;(2)阿拉斯加上空异常偏强高压脊前的冷空气造成锋区强度增加,使与行星锋区相关的高空急流异常偏强,两次过程降水区域分别位于高空急流入口区右侧及出口区左侧的上升运动区,大气对流层低层来自墨西哥湾充足的暖湿气流与强上升运动区相配合,造成了两个异常强的持续性降水阶段;(3)造成月平均降水量偏多与大型降水过程密切联系,而行星尺度波动为持续性降水过程提供了有利的大气环流背景条件和垂直运动条件。因此,在实际中期天气预报和短期气候预测中,应当充分考虑极地大气对流层超长波与极地外超长波、长波的位相配置在春季持续性极端强降水的作用。Based on NCEP/NCAR reanalysis data and CPC precipitation data,the reasons for the persistent heavy precipitation in the United States in May,2019 were analyzed.The study found(1)The configuration of planetary-scale wave phases at different latitudes in the northern hemisphere constitutes a circulation situation that is conducive to continuous precipitation An obvious 1 wave structure appears in the Arctic,and the mutual superposition of unusually strong 2,3,4 wave structurein the 45°N-60°N latitude zone,which create an abnormally stable circulation situation with a long duration.The superposition of the atmospheric ultra long and long waves with different wave numbers over Alaska and the thermal forcing of the warm Gulf of Alaska formed a high pressure ridge with large amplitude and slow movement.(2)The cold air in front of the abnormally strong high-pressure ridge over Alaska creates an increase in the strength of the frontal zone,which makes the upper level jet stream associated with the planetary frontal zone abnormally strong.The precipitation areas of the two processes are respectively located in the ascending movement area on the right side of the entrance area and the left side of the exit area of the upper jet stream.The sufficient warm and humid air from the Gulf of Mexico in the lower troposphere combined with the strong ascending movement area caused two exceptionally strong persistent precipitation stages.(3)The monthly mean precipitation is closely related to the large-scale precipitation process,and the planetary scale fluctuations provide favorable atmospheric circulation background conditions and vertical movement conditions for the persistent precipitation process.Therefore,in the actual medium-term weather forecast and short-term climate forecast,the role of the phase configuration of polar atmospheric tropospheric ultra-long wave,extra-polar ultra-long wave and long wave in the persistent extreme heavy precipitation in spring should be fully considered.

关 键 词：超长波、长波 同位相叠加 行星锋区 西风急流 持续性降水 

分 类 号：P426.61[天文地球—大气科学及气象学]