摘要
文中利用作者曾定义的东亚夏季风在中国东北地区 (12 2 .5°E ,4 0°N)的建立标准 ,根据相同的方法 ,分别计算了沿 112 .5 ,117.5 ,和 12 2 .5°E上 ,2 0°N及以北每隔 5个纬度东亚夏季风建立、持续和撤退时间 (候 ) ,将某年持续和多年平均持续候数相比的标准化值 ,定义为一种沿某一经圈上某一纬度的东亚夏季风强度指数ISMΦ,还分析了该指数与中国夏季降水量场和 5 0 0hPa高度场的相关。结果表明 :(1)沿 117.5°E经度上 ,东亚夏季风在 2 0 ,2 5 ,30 ,35 ,和 4 0°N建立的平均日期分别为 2 7.2 6 ,2 8.5 4 ,34.4 3,37.12和 37.6 5 (候 ) ,撤退平均日期分别为 5 4 .4 4 ,5 3.6 9,5 1.85 ,4 8和 4 6 .76 (候 ) ,其中 117.5°E ,2 0°N代表南海的中北部 ,文中确定的该区夏季风建立、撤退日期分别为 2 7.2 6 (候 )和 5 4 .4 4 (候 ) ,与国内学者公认的 5月 4候 (2 8候 )和 10月 1候 (5 5候 )相当吻合 ;(2 )沿 112 .5°E、117.5°E和12 2 .5°E的同一纬度上 ,东亚夏季风建立的平均日期并不相同 ,西边先于东边建立 ,每隔 5个经度 ,相差约 1～ 2候 ,而撤退的平均日期 (30°N及以北 )分布则相反 ,东边先撤退 ;(3)沿 117.5°E ,30°N和 35°N的ISMΦ和沿 12 2 .5°E ,4 0°N的ISMΦ均与中国华北和东北地区大部
In this paper, NCEP/NCAR 1948-2002 daily reanalysis data and monthly rain data in 151 stations archived in NCC were used to calculate the date of establishment and withdrawal of East Asia summer monsoon at every 5 latitude (north of 20°N) along 112.5, 117.5 and 122.5°E as well. The method is similar to the criterion of establishment and withdrawal of East Asia summer monsoon in Northeast China defined by us. A mean date [pentad] map of establishment and withdrawal of East Asian summer monsoon is drawn, an index of East Asia summer monsoon at a certain latitude along a certain longitude, I_ SMФ, is defined, and its relationship with summer precipitation and 500 hPa height in China was calculated. The results indicate that: (1) The mean pentads of establishment of East Asia summer monsoon at 20, 25, 30, 35 and 40°N along 117.5°E are 27.26, 28.54, 34.43, 37.12 and 37.65 respectively, and the mean pentads of its withdrawal are 54.44, 53.69, 51.85, 48 and 46.76 respectively. The determined pentad of establishment of East Asia summer monsoon in north of South China Sea(117.5°E, 20°N), is coincident with the 4th pentad in May recognized by China scholar. (2)The mean date of East Asia summer monsoon establishment at the same latitude is not the same along 112.5, 117.5 and 122.5°E, early in east part and preceding 1-2 pentad every 5 longitude. But the mean date distribution of its withdrawal (30°N and north of it) is opposite, first withdrawal in east part. (3) I_ SMФ indices along 117.5°E, 30, 35°N and 122.5°E, 40°N, are of positive correlation with July-August precipitation in North China and most of Northeast China; and of negative correlation with upper and lower reaches of Yangtze River (significance level α>0.05). This show that there is a good relationship between I_ SMФ and the main rain belt in summer in China mainland. (4) East Asia summer monsoon in China mainland subtropical region, represented by I_ SMФ, has a closed relationship not only with Subtropical High in west Pacific, but also with Okhotsk High in middle-high latitude; and summer monsoon in middle latitude region north of East China subtropical area has a more closed relationship with middle-high latitude general circulation. (5) An East Asia summer monsoon index I_ SMФ varied with longitude and latitude was explored. It is likely to avoid only single index of summer monsoon for a vast China land which would conceal the summer monsoon diversification from advance northward and withdrawal southward, and help further research on East Asia summer monsoon advance and withdrawal, law of its intraseasonal and interannual variation.
出处
《气象学报》
CAS
CSCD
北大核心
2004年第6期782-789,共8页
Acta Meteorologica Sinica
基金
国家自然科学基金项目 (4 0 2 75 0 19)
中国气象局科研重点项目"现代气候变化对吉林省西部荒漠化影响的监测和评估研究"
吉林省重点课题 (2 0 0 2 0 417
2 0 0 0 0 2 0 5 0 6
990 2 18)
