The Impact of Diurnal Variability of Sea Surface Temperature on Air-Sea Heat Flux Estimation over the Northwest Pacific Ocean

Accurate and consistent observations of diurnal variability of sea surface temperature (SST DV) and its impact on air-sea heat fluxes over large areas for extended periods are challenging due to their short time scale and wide coverage. The hourly gap-free SSTs generated from Japan Aerospace Exploration Agency-Japan Agency for Marine-Earth Science and Technology (JAXA-JAMSTEC) are input to the COARE3.5 bulk flux algorithm to investigate the impact of SST DV on air-sea heat fluxes over the Northwest Pacific Ocean (NWPO). The main results are as follows. (1) The JAXA-JAMSTEC SSTs were found to be in good agreement with the buoy observations on SST DV with a very slight negative bias of -0.007 degrees C and a root mean square error of 0.018 degrees C. (2) The case study conducted on 26 June 2020 showed that the fluxes' diurnal amplitudes were about 30-50 W m-2, and evolution was in agreement with SST DV. (3) The average impact of SST DV on heat fluxes was 2.93 W m-2 over the subtropical NWPO, decreasing from southeast to northwest and from low to high latitudes, and showing a clear seasonal cycle during 2019-2022. This research highlights the need to consider SST DV for accurate estimation of heat fluxes, which is crucial for climate and atmospheric studies.