Air-Sea Relationship Associated with Mesoscale Oceanic Eddies over the Subtropical North Pacific in Summer

A suite of high-resolution satellite and reanalysis data are used to investigate the coupling relationships between oceanic eddies and atmosphere over the subtropical North Pacific in the summer by means of eddy detection scheme and filtering and composite analysis. Results show that there are both positive and negative correlations between sea surface temperature (SST) and wind speed at 10 m over eddies on a daily time scale, which indicates that not only oceanic but also atmospheric forcing exists in mesoscale oceanic eddies. When SST is in phase with sea surface wind speed for warm (cold) eddies, upward (downward) net heat flux enhances, total cloud cover and precipitation increase (decrease); the sea water temperature anomalies and current curls enhance, and thus warm (cold) eddies are relatively stronger. All of these changes indicate the ocean-to-atmosphere forcing to a certain extent. In addition, when SST is in opposite phase with sea surface wind speed for warm (cold) eddies, downward (upward) net heat flux enhances, total cloud cover and precipitation decreases (increases) with positive (negative) anomalies of geopotential height and air temperature at the low-middle levels, and negative (positive) anomalies of relative humidity. Moreover, the sea water temperature anomalies and current curl are weakened, and warm (cold) eddies are relatively weaker. All of these are conducive to the maintenance of warm (cold) eddies under clear (rainy) sky, indicating the atmosphere-to-ocean forcing to a certain extent.