1998年夏季风爆发前后南海地区的水汽输送和水汽收支

THE MOISTURE TRANSPORT AND MOISTURE BUDGET OVER THE SOUTH CHINA SEA BEFORE AND AFTER THE SUMMER MONSOON ONSET IN 1998

关键词:  南海夏季风  水汽输送  水汽通量散度

Key words:  summer monsoon over the SCS  moisture transport  moisture flux divergence

摘要:

根据1998年南海夏季风试验期间GAME/HUBEX一天4次同化资料,着重分析了1998年南海夏季风爆发前后大尺度水汽输送的主要特征,结果表明大尺度水汽条件与季风活动密切相关。南海夏季风爆发前后,南海地区主要的水汽输送带发生了较大变化。季风爆发前,南海地区水汽主要来自西太平洋;季风爆发后,水汽主要来自热带东印度洋和孟加拉湾。降水过程与水汽辐合的极大值密切相关,而主要水汽辐合带位置的移动及强度的变化则和南海夏季风相联系。随着南海夏季风的建立、加强,南海地区的水汽辐合带相应地建立和加强,并伴有降水发生。季风爆发后南海地区大气的可降水量较季风爆发前显著增加。季风爆发前大气的水汽汇中心主要出现在中南半岛及我国华南沿海地区,南海夏季风爆发后,从孟加拉湾到南海水汽输送加强,南海大部、孟加拉湾北部和菲律宾以东的洋面上均转为水汽汇区,从而对南海、日本及其以南的降水产生重要影响。

Abstract:

Based on the assimilation data four times a day from GAME/HUBEX during the summer monsoon onset period over the South China Sea (SCS) in 1998, the main characteristics of the large-scale moisture transport were analyzed. It suggested that the moisture condition was closely associated with the activities of the summer monsoon. Before and after the monsoon onset over the SCS, the moisture transport belt over the SCS changed greatly. Before the monsoon onset , the moisture over the SCS was mainly from the western Pacific Ocean; while after the monsoon onset the moisture was mainly from the eastern tropical Indian Ocean and the Bay of Bengal. The process of precipitation was related with the maximum of the moisture convergence, while the location and intensity of the moisture convergence was related with the summer monsoon over the SCS.With the establishment and enforcement of the summer monsoon over the SCS, the convergence belt of moisture over the SCS correspondingly set up and enhanced, and precipitation occurred. After the monsoon onset, the precipitable water increased apparently as compared with that before the monsoon onset. Before the monsoon onset, the moisture sinks mostly appeared in the Indo-China Peninsula and the coastal areas of South China. After the monsoon onset, the moisture transport from the Bay of Bengal to the SCS enhanced and the moisture sinks moved to most part the SCS, the northern part of the Bay of Bengal and the ocean to the east of the Philippine, which produced important effect on the precipitation over the SCS, Japan and its southern region.