南海北部海区下降流及其对环流的影响研究

下降流是指海水从上层向下层运动的过程。研究南海北部海区下降流的特征和机制，对于进一步认识该海区环流、垂向水体结构变化等过程具有重要的科学意义。本项目拟采用多种观测手段与分析方法从三个主要方面研究南海北部的下降流。（1）利用历史资料和加密的大面补充观测，明确南海北部海区下降流区温、盐和流场结构等基本特征及其空间分布；（2）利用在南海北部典型下降流区跨陆架布放配备有多种先进海洋调查仪器的锚系潜标阵列，获取海洋多参数的长时序观测，以揭示下降流的时间变化以及形成和变化的机制，包括风、地形变化以及海水浮力变化等因素对下降流的作用，并结合遥感资料和再分析数据等进一步揭示南海北部深海区中尺度涡对下降流的作用；（3）应用再分析资料阐明下降流对于南海北部环流三维结构的影响，并探讨下降流对局地海洋表层与内部物质交换的影响。本项目预期在南海北部海区下降流的动力学过程及其局地影响等方面取得一些创新性的研究成果。

Downwelling is a sinking process that carries sea water from upper ocean to the interior. Improved understanding of characteristics and mechanisms of downwelling in northern South China Sea (SCS) is of scientific significance for a better knowledge of regional circulation and vertical structure of water mass. Based on multiple observational and analytical methods, this proposal aims to investigate downwelling in the northern SCS from three aspects. (1) Using historical data and well-designed complementary cruise measurements, we plan to obtain the basic characteristics of downwelling in the northern SCS, specifically the structures of temperature, salinity and velocity. (2) Based on a mooring array with a cross-shelf orientation and onboard with multiple advanced instruments, we can get long time series of oceanographic properties. This data set is intended to help revealing the mechanisms of downwelling generation and variability, such as effects of wind, bottom topography, and buoyancy changes. Remote sensing and reanalysis data will also be used to further reveal the role of mesoscale eddies in downwelling. (3) The role of downwelling in regional three-dimensional circulations and local exchange of properties between the ocean surface and interior will be examined using reanalysis data. This project is expected to gain novel results and an improved understanding of the dynamics of downwelling in northern SCS as well as its regional effects.