Intraseasonal oscillation features of the South China Sea summer monsoon and its response to abnormal Madden and Julian Oscillation in the tropical Indian Ocean

• Published in: Science China. Earth sciences Vol. 56; no. 5; pp. 866 - 877
• Main Authors: Li, Ting, Yang, XiuQun, Ju, JianHua
• Format: Journal Article
• Language: English
• Published: Heidelberg SP Science China Press 01-05-2013; Springer Nature B.V
• Subjects: Annual variations; China; Convection; Earth and Environmental Science; Earth Sciences; Hydrologic data; Latitude; Longitude; Marine; Meteorology; Monsoons; Ocean-atmosphere interaction; Oscillations; Phases; Rainfall; Research Paper; Spreads; Summer; Tropical environments; 中国南海; 亚热带地区; 南海夏季风; 南海季风; 季节内振荡; 热带印度洋; 特征和; 降水异常; ISEW, South China Sea; ISW, Bangladesh, Bengal Bay; ISW, Tropical Indian Ocean; China, People's Rep; MJO; ISO; relay spread in the longitude-latitude direction; South China Sea (SCS) summer monsoon (SCSSM); tropical Indian Ocean
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-012-4521-1

By applying the OLR and wind data, rainfall data and the Madden and Julian Oscillation （MJO） index, the paper deals with in traseasonal oscillation features and interannual differences of the South China Sea （SCS） summer monsoon, distribution of its LF circulation and convection fields and rainfall, and path of summer monsoon ISO spreading, as well as impact of tropical IndoMJO on SCS summer monsoon ISO during 19792008. It is found that （1） there are three intraseasonal oscillations of the SCS summer monsoon Intraseasonal Oscillation （ISO） in summer （from May to August） in the climate normal. The SCS summer monsoon ISO goes through six phases （exclusive of weak phase） at every complete fluctuation： developing, the strongest, weakening, restraining, the weakest, and recovering. Due to tropical LC convection spreading to the east and north, the LR convection and circulation fields in the lst3rd and 4th6th phases present the antiphase in the Arabian SeaWest Pa cific latitudinal band. Its corresponding rain bands in the lst3rd and 4th6th phases als present antiphase roughly. The rain band, mainly in tropical regions in the south of 20N, moves eastward with LR convection shifting eastward, while the rain band moves northward with LR convection shifting northward in East Asia （EA） subtropical regions in the north of 20N. （2） The SCS summer monsoon ISO presents significant interannual variations in intensity. There are three stronger monsoon in traseasonal oscillations in summer in the strong SCS monsoon ISO year. The first two oscillations from the tropical Indian Ocean ISO spread northward to the Bay of Bengal first, and then to the South China Sea （SCS） along the 10-20N latitudinal band. They are strengthened there and stimulate the ISO moving to the north to form the tropical IndoISO. Finally they spread to South China （SC） by relay way in the longitudelatitude direction. Moreover, in the weaker SCS summer monsoon ISO, the oscillation weakens greatly and irregularly in intensity with the weaker ISO spreading in the longitudelatitude direction. In average conditions, the tropical Indian ISO spreads to the SCS by about 20 days （one half ISO periods）. （3） MJO1 （the first modal of MJO index provided by the CPC） averaged value in the lst2nd pentads of April has the negative correlation with the SCS monsoon ISO intensity. The tropical IndoMJO is slightly stronger in the subsequent May to August when it is more ac tive in the lst2nd pentads of April, and the ISO also spreads strongly to the SCS, so that the SCS summer monsoon ISO strengthens. Conversely, the SCS summer monsoon ISO weakens. The abnormal MJO in the lst2nd pentads of April contrib utes to a certain theory basis for us to predict the subsequent SCS summer monsoon ISO intensity and analyze the related re gions＇ abnormal rainfall.