Satellite observed quick shift events of the wind jet over the South China Sea in summer and its impacts on the ocean circulation

The 17 year record of daily sea surface wind observed from the QuikSCAT and ASCAT satellite scatterometers from 2000 to 2016 is used to study quick shifting wind jet events over the South China Sea (SCS) in summer. The wind jet typically undergoes a counter-clockwise rotation from eastward to northward in about 8 days and then back to eastward in roughly 4 days. Generally, the entire cycle takes between 4 and 21 days. Such events happen 2-6 times every summer and, in total, have occurred 72 times over the last 18 years. Model simulations demonstrate that the wind stress curl associated with quick wind shifts deform the double gyre in the SCS, with a conspicuous weakening of the northern gyre and a northwestward movement of the center of the southern gyre. In addition, a quick shift of the wind jet leads to both negative sea surface temperature (SST) anomalies in the SCS that lag about one day because of the surface latent heat flux, and positive SST anomalies around the eastward current because of decreased cold advection.

Automated summary

The study utilizes 17-year satellite data to analyze the quick shifting wind jet events over the South China Sea in summer. The findings reveal that the wind jet undergoes a counter-clockwise rotation from eastward to northward in about 8 days and then back to eastward in roughly 4 days. The entire cycle takes between 4 and 21 days and occurs 2-6 times every summer. Model simulations show that the wind stress curl associated with quick wind shifts deforms the double gyre in the South China Sea, leading to a weakening of the northern gyre and a northwestward movement of the center of the southern gyre. Additionally, the quick shift of the wind jet results in both negative sea surface temperature anomalies in the South China Sea and positive anomalies around the eastward current.