Which surface atmospheric variable drives the seasonal cycle of sea surface temperature over the global ocean?

Abstract

The impact of near‐surface atmospheric variables used in driving the seasonal cycle of climatological mean sea surface temperature (SST) is quantified over the global ocean. The six atmospheric variables are air temperature, vapor mixing ratio, wind speed, precipitation, net shortwave radiation, and net longwave radiation, the first (last) three just above (at) the sea surface. Atmospherically forced ocean general circulation model (OGCM) simulations with no data assimilation are performed using monthly and annual means of those variables under the assumption that variations in climatological monthly SSTs are driven by atmospheric variables. SSTs resulting from these simulations are compared with those from a satellite‐based field to determine the impact of each atmospheric variable. Large spatial variability is found in the order of impact (most to least) of six atmospheric variables. In general, the SST seasonal cycle is driven primarily by shortwave radiation at midlatitudes, but wind speed is the major controlling variable in the Indian Ocean. Precipitation has almost no significant influence on monthly SST. Overall, shortwave radiation is the most influential variable controlling the seasonal cycle of SST over 34.3% of the global ocean. Wind speed is the second most important variable (27.2%). In tropical regions and the Arabian Sea, sources other than the atmospheric thermal forcing are found to play a significant role in regulating the SST seasonal cycle.