Using TPI to Map Spatial and Temporal Variations of Significant Coastal Upwelling in the Northern South China Sea

Weian Shi,Jianyu Hu,Zhi Huang

doi:10.3390/rs13061065

Abstract

Based on Himawari-8 Sea Surface Temperature (SST) data and the semi-automatic Topographic Position Index (TPI)-based mapping method, this study maps the significant coastal upwelling in the northern South China Sea (NSCS). The results show that the Minnan coastal upwelling mainly occurs within 100 km off the south coast of Fujian; the Yuedong coastal upwelling appears to the east of Pearl River Estuary, limited to the area shallower than 40 m; and the Qiongdong coastal upwelling occurs most frequently in the area shallower than 75 m off the east coast of Hainan Island. Based on the results, this paper quantitatively describes the temporal and spatial variations of upwelling duration, influence area, upwelling SST anomaly, and chlorophyll-a (Chl-a) increase. Different coastal upwelling regions in the NSCS are significantly different in characteristics. The Qiongdong coastal upwelling has the longest duration and occurs most frequently, the Yuedong coastal upwelling has the largest influence area and Chl-a increase, and the Minnan coastal upwelling is quite strong in the NSCS.

Highlights

Qiongdong coastal upwelling has the longest duration and occurs most frequently, the Yuedong coastal upwelling has the largest influence area and Chl-a increase, and the Minnan coastal upwelling is quite strong in the northern South China Sea (NSCS)
China seas and summarized their characteristics and new progresses. They pointed out that the coastal upwelling in the NSCS mainly occurs off south coast of Fujian, east coast of Guangdong, and east coast of Hainan Island, and the coastal upwelling is mainly driven by the southwesterly monsoon in boreal summer
We used upwelling index and wind stress curl to discuss the mechanisms of coastal upwelling

Summary

Introduction

Qiongdong coastal upwelling has the longest duration and occurs most frequently, the Yuedong coastal upwelling has the largest influence area and Chl-a increase, and the Minnan coastal upwelling is quite strong in the NSCS. The coast of the northern South China Sea (NSCS) features seasonal coastal upwelling during the boreal summer [2]. China seas and summarized their characteristics and new progresses They pointed out that the coastal upwelling in the NSCS mainly occurs off south coast of Fujian (called Minnan coastal upwelling hereafter), east coast of Guangdong (called Yuedong coastal upwelling hereafter), and east coast of Hainan Island (called Qiongdong coastal upwelling hereafter), and the coastal upwelling is mainly driven by the southwesterly monsoon in boreal summer. Since Hu and Wang [3], there have been some studies on the upwelling in the SCS using the remotely sensed data [4,5,6,7,8]. Combining the Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature (SST) data with the European Center for Medium-Range

Objectives

Methods

Results

Conclusion