大气科学2012，Vol.36Issue(4)：722-732,11.DOI:10.3878/j.issn.1006-9895.2011.11076
东亚副热带西风急流活动与长江中下游梅雨异常关系的研究
A Study of the Relationship between East Asia Subtropical Westerly Jet and Abnormal Meiyu in the Middle-Lower Reaches of the Yangtze River
摘要
Abstract
By using the daily reanalysis data provided by National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP/NCAR) and daily precipitation data at 2000 BT (Beijing time) from 714 Chinese meteorological stations during period 1960-2009,the relationship between the East Asia subtropical westerly jet (EASWJ) and abnormal typical,atypical Meiyu in the middle-lower reaches of the Yangtze River is analyzed during the Meiyu season,the mechanism of the influences of EASWJ on Meiyu is studied,the significance of monitoring and analysis of the EASWJ to middle-range forecasting for Meiyu is discussed.The composite analysis during Meiyu seasons shows the EASWJ would be stronger,the jet band is narrow and the jet mass and momentum concentrate in the abnormally typical Meiyu year compared to those in the atypical Meiyu year.Daily evolution of the EASWJ is marked by following characters: In typical (atypical) Meiyu years,the jet swings steadily around its climatological position in meridional orientation (with large amplitude); the zonal wind is stronger (weaker) in the key region of (30癗-37.5癗,110癊-130癊); the location of jet core is mainly around 125癊 (145癊) from East Asia to the western Pacific,which is near to (away from) the east of China and locates on the leeward side.The study of influence mechanism on abnormal Meiyu shows that,in typical Meiyu years,200-hPa axis line of the EASWJ,zero line of divergence,and zero line of divergence departure coincide at 37.5癗 in the east of China,convergence is in the north of the jet axis and divergence is in the south of the jet axis,the region of divergence center coinciding with that of divergence departure center locates above the middle and lower reaches of the Yangtze River,the above items cooperating with strong divergence flowing out at upper levels,strong convergence at lower levels,and strong vertical ascending movement from lower to upper levels provide favorable dynamical condition for Meiyu; the jet coupling between lower and upper levels is helpful for the enhancement of southwest wind at lower levels,and thus the southwest vapor flux departure exists in the south of the middle-lower reaches of the Yangtze River,which provides favorable condition for water vapor transportation; strong subtropical frontal zone at upper levels cooperating with typical steep and straight Meiyu frontal zone is beneficial to maintaining of jet mass and momentum,which also provides favorable condition for the developing of deep convection.Opposite situations are observed in atypical Meiyu years.By considering middle-range character of the EASWJ by monitoring and analyzing its integrated aspects of intensity,position,and variation,it is helpful to clearly realize and explain the influence of EASWJ on Meiyu and its corresponding mechanisms,which also contributes to improvement in middle-range forecasting for Meiyu.关键词
东亚副热带西风急流/逐日演变/梅雨异常/影响机理/中期预报Key words
East Asia subtropical westerly jet, daily evolution, abnormal Meiyu, influence mechanism, middle-range forecasting分类
天文与地球科学引用本文复制引用
金荣花,李维京,张博,闫彩霞..东亚副热带西风急流活动与长江中下游梅雨异常关系的研究[J].大气科学,2012,36(4):722-732,11.基金项目
科技部国家科技支撑计划项目2009BAC51B03,公益性行业(气象)科研专项GYHY(QX)GYHY200906007,中国气象局气象新技术推广项目重点项目CMATG20092D02 （气象）
