基于HYCOM模拟的南海西北部环流

Northwest South China Sea Circulation Based on HYCOM Simulation

关键词:  南海  北部湾  琼州海峡  环流  HYCOM

Key words:  South China Sea  Beibu Gulf  Qiongzhou Strait  circulation  HYCOM

摘要:

为研究北部湾在内的南海西北部海域环流结构的时空特征，本文基于Hybrid Coordinate Ocean Model（HYCOM）模式和气象强迫数据，通过三重嵌套模拟研究南海西北部环流在风力强迫下的结构及其时空分布特征，结果表明：（1）南海西北部流场受季风影响较大，冬季基本为西南向流，夏季基本为东向流，流场结构复杂，外海涡旋众多，Ekman运动特征较为明显；（2）北部湾流场呈现出较强的密度流特征，冬季基本为气旋式环流，夏季同时存在较小尺度的气旋式和反气旋式环流；7月湾口表层的气旋式环流结构向下直接影响到海底；（3）北部湾的海表面盐度受蒸发降雨影响较大，盐度分布西低东高，这与湾口和琼州海峡入侵的南海高盐海水有关；（4）在热盐作用和季风驱动下，琼州海峡的表、底层流冬季为西向流，夏季为东向流，冬季广东沿海地区的富营养化海水可能通过琼州海峡影响广西近海海域环境质量。

Abstract:

In order to study the spatiotemporal characteristics of the circulation structure in the northwestern part of the South China Sea, including Beibu Gulf, based on Hybrid Coordinate Ocean Model (HYCOM) and meteorological forcing data, triple nested simulations were used to study the structure and spatial and temporal distribution characteristics of the northwestern South China Sea circulation under wind forcing. The results show that,(1) the Northwest SCS circulation is significantly affected by monsoon. It is generally a southwestern flow in winter and an eastward flow in summer. The structure current field is complicated, and there are many vortices in the open sea. The Ekman pumping is vigorous in these areas. (2) The current field of Beibu Gulf presents a strong density flow characteristic. It is basically a cyclonic circulation in winter, and there are smaller-scale cyclonic and anti-cyclone circulations in summer. The cyclonic circulation structure at the surface of the bay mouth in July directly affects the ocean floor. (3) The sea surface salinity of Beibu Gulf is greatly affected by evaporative rainfall. The salinity distribution is low in the west and high in the east, which is related to the high salinity of South China Sea invaded through the mouth of the bay and Qiongzhou Strait. (4) Driven by the effects of hot salt and monsoon, the surface and bottom currents of the Qiongzhou Strait are westward in winter and eastward in summer. In winter, eutrophic seawater in the coastal areas of Guangdong may affect the environmental quality of offshore waters in Guangxi through Qiongzhou Strait.