夏季北黄海南部定点高分辨率实测海流分析

Analysis of the high-resolution observed current data in the southern area of the North Huanghai Sea in summer

对夏季北黄海南部一定点高分辨率连续ADCP(Acoustic Doppler Current Profiler)海流实测资料,使用调和分析方法分解成3部分:不随时间变化的定常余流,周期性潮流和剩余流,再将潮流分解为正压潮流和斜压潮流。通过对实测海流中各组分的分析,结合同时期卫星反演海面风场资料,温度、盐度断面调查资料,得到以下结论:夏季该站点上层定常余流的主导动力控制因素是风应力,上层表现出明显的Ekman风海流特征,中、下层流速方向与表层流向基本成反向,体现出"上进下出"的垂向空间结构,定常流速最大位于近表层,可以达到5cm/s以上;各层的潮流类型均为正规半日潮流,主要半日潮潮流椭圆长轴的方向基本上呈东南-西北方向,其椭率在近底层达到最大值,中、上层较小;从能量角度分析该站点各海流组分,潮流与剩余流所占能量较大,平均起来看,潮流能量占测量海流能量的77%,而定常余流仅占0.6%,该点的斜压潮流较弱,平均斜压潮流能量仅占正压潮流能量的5%。

The harmonic analysis method is used to analyze the high-resolution successive observed acoustic doppler current profiler （ADCP） data on a fixed station, which is located in southern area of the North Huanghai Sea. The current data is decomposed into three components, steady current which is not changing with time, periodical tidal currents and residual current, further the tidal current is decomposed to barotropic tidal current and baroclinic tidal current. By analyzing the components of the observed current, combining with the satellite data about the sea surface wind field, surveyed temperature profile and salinity profile data during the same period, the analysis results show that the major dynamic control factor of the steady current in the upper layers on this station is wind stress in summer, and the characteristics of the Ekman current is quite obvious, however, the steady current direction in the middle and lower layers is opposite to direction in the upper layers. Basically, it shows a vertical spatial structure ＂flow inward in the upper layer and flow outward in the lower layer＂. The largest velocity of the steady current is near the surface which is larger than 5 cm/s nearly. The tidal current in each layer belongs to the regular semi-diurnal tidal currents type, the long axis direction of the major semi-diurnal tidal currents ellipse is the southeast- northwest. Basically, the maximum of tidal ellipse curvature appears near the bottom layer. In the view of the ocean current energy, the tidal current and the residual current takes large proportion on average, the ratio between the tidal current energy and the observed current energy is 77%, but the ratio of the steady current energy is only 0. 6%, the baroclinic tidal current in this station is weak, and the ratio between the energies of baroclinic and barotropic tidal current components is only 5 %.