Evolution of surface cold patches in the North Yellow Sea based on satellite SST data

Abstract

Ten years (from 2005 to 2014) of satellite sea surface temperature (SST) data from the Advanced Very High Resolution Radiometer (AVHRR) are analyzed to reveal the monthly changes in surface cold patches (SCPs) in the main areas of the Northern Yellow Sea (NYS). The Canny edge detection algorithm is used to identify the edges of the patches. The monthly changes are described in terms of location, temperature and area. The inter-annual variations, including changes in the location and area of the SCPs from 2010 to 2014, are briefly discussed. The formation mechanisms of the SCPs in different periods are systematically analyzed using both in situ data and numerical simulation. The results show that from May to October, the location and area of the SCPs remain stable, with a north-south orientation. The SCPs altogether cover about 1° of longitude (124°E–125°E) in width and 2° of latitude (37.5°N–39.5°N) in length. In November, the SCP separates from the Jangsan Cape and forms a closed, isolated, and approximately circular cold patch in the central NYS. From May to October, the upwelling that leads to the formation of the SCP is mainly triggered by the headland residual current, wind field, climbing movement of the current and secondary circulation at the tide front. In November, cyclonic circulation in the NYS is primarily responsible for generating the upwelling that leads to the formation of the closed and isolated SCP.