南海中西部渔场上升流时空变化特征分析

Analysis of the upwelling in the fishing ground in Midwestern South China Sea

南海中西部海域是我国外海渔业开发的潜在渔场之一，摸清该海域的物理环境特征可为我国开发中西部渔场提供参考。本文以遥感风场和海温数据为基础，分析了2003～2012年西南季风期起止时间的年变化、上升流中心位置时空变动以及风场对上升流中心位置变动的影响。结果表明：在南海中西部海域，西南季风期通常从5月份开始，到9月份结束，西南季风持续天数平均值为129．4d，其中，风向角呈51°～60°的天数最多，占总季风天数的21．98％，西南季风期持续时间有增加的现象。上升流中心位置变动范围为11°～15°N，109°～112°E。西南季风期平均风速减小时，年平均上升流中心在经向上向近岸移动，在纬向上向高纬度移动；平均风速增加时，年平均上升流中心在经向上向离岸方向移动，在纬向上向低纬度移动；当西南季风期平均风向角减小时，年平均上升流中心向低纬度移动，平均风向角增大时，年平均上升流中心向高纬度移动。此外，发现厄尔尼诺年此上升流面积显著大于非厄尔尼诺年，而最低温度比2003～2012年平均最低温度低1.3℃。

The Midwestern South China Sea is one of the potential fishing ground in Chinese marine fishery. To study the characteristic of the upwelling in Midwestern South China Sea can give a great help to realize the fishing ground for China. In the paper, both satellite wind and sea surface temperature （SST） data were used to study the annual variations of southwest monsoon, the spatial and temporal distribution of upwelling center, and the effect of wind on variations of the upwelling center. The results show that the southwest monsoon mainly began in May and ended in September from 2003-2012. The average duration of southwest monsoon was about 129.4 each year. The main wind angle is 51°-60° in southwest monsoon. The proportion between the days with wind angle of 51°-60° and the days of southwest monsoon is 21.98%. The duration of southwest moon presented an increasing trend from 2003 to 2012. The distribution of the centers of upwelling varied in the region ll°-15°N, 109°-112°E. When the wind speed decreased, the annual center of upwelling moved to nearshore and higher latitude regions, while when the wind speed increased, the annual center of upwelling moved to offshore and lower latitude regions. When the wind angle decreased, the center of upwelling moved to lower latitude region, while when the wind angle increased, the center of upwelling moved to higher latitude region. ENSO enhanced the area of upwelling compared to non-ENSO year. The lowest SST in ENSO year was 1.3 ℃ lower than the mean value of lowest SST from 2003-2012.