Diurnal Forcing Causes Dipole-type Modification on Summer Salinity in the East China Sea and Its Formation Mechanism
Abstract
The impact of diurnal atmospheric forcing on the summer salinity change in the East China Sea was investigated using the Regional Ocean Modeling System, forced by the hourly versus, by daily wind and insolation reanalysis data. The differences between these two frequency forcing revealed a dipole pattern of salinity change with a positive salinity deviation (1~2 PSU) offshore of the Yangtze River estuary, and a negative deviation (-1~-0.5 PSU) along the Jiangsu Coast. Further dye tracking experiments confirmed that the diurnal forcing strengthened the northwestward longshore freshwater transport (NLFT) of Yangtze River by 5.2×109 m3 and reduced the mean water age of 7 days over the region. Sensitivity experiments that use different forcing combinations suggested that the diurnal wind, i.e. the land-sea breeze, was the key to explaining the dipole-pattern salinity deviation and the NLFT changes. The land-sea breeze induced a clockwise mean circulation anomaly offshore of the Yangtze River estuary. This occurred through the baroclinic adjustment process related to the diurnal density (salinity) variation, which is correlated to the diurnal swing of the Yangtze River front. The baroclinic adjustment generated a dipole pattern of vorticity change offshore of the Yangtze River estuary, the coherent jet current strengthened the NLFT, explaining the summer dipole pattern of the salinity difference.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMOS11D1502Y
- Keywords:
-
- 4299 General or miscellaneous;
- OCEANOGRAPHY: GENERAL;
- 4599 General or miscellaneous;
- OCEANOGRAPHY: PHYSICAL