江淮梅雨季副高特征及降水特征分析

Analysis on Characteristics of Subtropical High and Precipitation in Jianghuai Meiyu Season

针对梅雨季节江淮地区降水和副高活动特征,结合副高指数定义,对长时间序列的副高指数及北跳时间进行定量化统计。通过分析1979-2018年6-7月NCEP/NCAR逐日再分析资料和国家气象站日降水资料,统计40年副高3项指数的逐年逐日变化,并分析指数异常年的大气环流特征。同时,研究江淮地区梅雨季的降水特征,对副高北跳与高度场、降水量的关系进行系统分析,研究结果表明:6-7月,副高脊线随时间逐渐向北移动,西伸脊点逐渐西移,副高面积逐渐扩大,副高强度增强;1979-2018年江淮地区梅雨季期间,副高3项指数均为异常的年份有5年,负异常年,中纬度槽脊的波动平缓,经向运动微弱,正异常年,西风带上气流的经向运动加强,40年气候态上表现为长波两槽两脊形势;梅雨季节副高的两次北跳过程中,第一次北跳出现在6月第三侯,第二次北跳在7月第三侯,气候态表现为第二次北跳在第一次北跳后约7侯出现;降水的空间分布存在着明显的南北、东西差异,江淮地区500 hPa高度场与副高的第一次北跳呈明显负相关,与副高第二次北跳呈正相关。

According to the characteristics of precipitation and activity of subtropical high in the Jianghuai region during the Meiyu season,the subtropical high index and northward jump time of the long time series were quantitatively counted in combination with the definition of subtropical high index.By analyzing the daily reanalysis data of NCEP/NCAR and the daily precipitation data of national meteorological stations in June and July from 1979 to 2018.the daily variation of the three subtropical high indexes in the 40 years were statistically analyzed,and the characteristics of atmospheric circulation in the index abnormal years were analyzed.At the same time,the thesis analyzes the precipitation characteristics of the Meiyu season in the Jianghuai region,and the relationship between the north jump of subtropical high and the height field and precipitation is analyzed systematically.The results show that,during June and July,the ridgeline of the subtropical high moved northward,the ridge point of the western extension moved westward,the area of the subtropical high expanded gradually,and the intensity of the subtropical high increased.During the Meiyu season in the Jianghuai region from 1979 to 2018,there were 5 years in which all three indices of subtropical high were abnormal.In negative anomaly years,the fluctuation of trough ridge in mid-latitude was gentle,and the meridional motion was weak.In positive anomaly years,the meridional movement of the airflow over the westerlies is strengthened.The climate state of 40 years shows the situation of the long wave,two troughs,and two ridges.During the two northward jumps of the subtropical high in the Meiyu season,the first northward jump occurred in the 3 hou of June,the second northward jump occurred in the 3 hou of July.And the climatic state showed that the second northern jump appeared about 7 hou after the first one.The spatial distribution of precipitation has obvious north-south and east-west differences.The 500 hPa height field in the Jianghuai region is significantly negatively correlated with the first northward jump of subtropical high and positively correlated with the second northward jump of subtropical high.