西太平洋热带涡旋与2001年南海夏季风的爆发

WEST PACIFIC TROPICAL VORTEX AND SOUTH CHINA SEA MONSOON ERUPTED IN 2001

利用NCEP/NCAR再分析格点资料普查1950—2004年南海夏季风爆发前后850hPa的天气形势图,发现大多数年份,在南海夏季风建立的前5天,菲律宾以南海域(0～10°N,125～140°E)常伴有一次西太平洋热带涡旋的活动过程。选取南海夏季风爆发偏早的2001年进行个例分析,结果表明随着西太平洋热带涡旋的发展和移动,南海地区的正涡度不断增加,使得西太平洋副热带高压减弱东退,南海夏季风爆发。对涡旋区和南海地区的涡度、热源、水汽汇等进行区域平均,发现南海地区正涡度的增大,热源、水汽汇的加强很大程度上是由于西太平洋热带涡旋作用所致,西太平洋热带涡旋的作用可能是2001年南海夏季风爆发的重要因子之一。

Using NCEP/NCAR reanalysis data to survey 1950--2004 year＇s synoptic chart during the time of South China Sea Monsoon（SCSM） eruptions, we find out during most years, before the eruption of SCSM, the West Pacific Tropical Vortex always appears in the sea area to the south of Philippine（0-10 °N, 125- 140 °E）. Then choosing the 2001-year which SCSM erupted earlier than normal as an example and making analysis, the results indicate that the development and movement of West Pacific Tropical Vortex augment the local vorticity of Nanhai area where used to be controlled by the ridge of Subtropical High. And the positive vorticity of Nanhai area is increasing constantly, forcing the ridge of Subtropical High weaker and weaker, after the Subtropical High moves eastward, the SCSM breaks out. At last, averaging the vortex area＇s and Nanhai area＇s vorticity, heat source, water vapor sink etc, we find that the increasement of positive vorticity, heat source, water vapor sink in Nanhai area may be caused by the West Pacific Tropical Vortex actives.