风对南海波浪的能量输入及其长期变化

摘要

The energy of winds into surface waves in the South China Sea during 1871-2008 was estimated by using the ocean reanalysis data of SODA (simple ocean data assimilation) 2.2.4 (1871-2008). The results showed that the annual wind energy input is about 0.2 TW, and that the spatial pattern of this kind of input is mainly located in the northern parts of the South China Sea during winter and in the southern parts in summer;and the intensity of summer input is much weaker than that of winter. Similar results were obtained by using the ERA-40 (European Centre for Medium-Range Weather Forecasts re-analysis-40) (1957-2002) and ERA-20C (1900-2010) data sets. The secular trend of wind energy input into waves was reduced at the rate of 0.43%per year since 1950. We also studied the swells and wind waves, which are two categories of the waves, by using the ERA-interim data. The spatial pattern of wind energy input into the swells and wind waves is mainly located in the northern parts of the South China Sea, but there is also a high wind energy input into the wind waves area in the southern parts of the South China Sea. The secular trend of the wind energy input into swells was increasing, and the same trend of wind energy input into the wind waves was reducing; the total energy input was also reducing by the joint effect of swells and wind waves. All of this was thanks to the weakening East Asian monsoon, which dominated in the South China Sea, in recent decades. These results are significant for understanding the variation of the surface waves in the South China Sea.%利用美国的全球海洋同化资料SODA(simple ocean data assimilation)2.2.4(1871—2008)中的风应力数据,估算了风输入给南海波浪的能量。结果表明,风向南海波浪输入能量的年均值约为0.2TW,其空间分布冬季以南海北部为主,夏季以南部为主且强度比冬季要弱得多；风对南海波浪能量的输入一直呈减少趋势,用欧洲中期天气预报中心的再分析资料ERA-40(European Centre for Medium-Range Weather Forecasts re-analysis-40)(1957—2002)和ERA-20C(1900—2010)中的风场和海浪资料得到的趋势也是如此,1950年以来每年减少0.43%。用ERA-interim(1979—2014)中的有效波高数据可以把风给风浪和涌浪的能量输入区分开,两者的空间分布皆以南海北部为主,而给风浪的能量输入在南海南部还有一个高值区。尽管风输入给涌浪的能量略有增加,但给风浪的能量输入在不断减少,两者之和仍是减少。究其原因,控制南海的东亚季风最近几十年一直在减弱。这些结果对认识南海波浪未来的变化及其预报具有意义。