Diurnal Sea Surface Temperature Response to Tropical Cyclone Dahlia in the Eastern Tropical Indian Ocean in 2017 revealed by the Bailong Buoy

Abstract Tropical Cyclone (TC) Dahlia occurred adjacent to over the equatorial southeastern Indian Ocean during the period 26 November – 3 December 2017 and was observed by the Bailong buoy, which provides in situ observations of high-frequency variations in the upper ocean environment. The diurnal sea surface temperature (dSST) variabilities during different stages of the passage of TC Dahlia are studied. The dSST variability is rather weak during the TC passing stage in contrast to the strong ranges before (0.35 °C) and after (0.57 °C) the TC. Before the influence of TC Dahlia, the dSST presented significant regular variability with a peak in the afternoon and minimum value in the morning, which is similar to the even larger range that occurred after TC Dahlia. During the passage of TC Dahlia, dSST decreased dramatically, and a uniform variation was presented due to the absence of strong heat fluxes and stirring and upwelling induced by strong winds. Further analysis through a one-dimensional mixed layer model (Price-Weller-Pinkel, PWP) indicated that the dominant elements responsible for the different dSST variations during distinct stages of TC Dahlia were shortwave radiation and surface wind, which strongly impacted the dSST evolution during TC Dahlia. The asymmetrical wind strength was responsible for the asymmetry of dSST variation.