[A-CG33] Multi-scale ocean-atmosphere interaction in the tropics

[ACG33-P04] Diurnal SST warming and the boreal summer intraseasonal oscillation in the Philippine Sea

*Ayako Seiki¹, Akira Nagano¹, Ning Zhao¹, Iwao Ueki¹, Satoru Yokoi¹ (1.Japan Agency for Marine-Earth Science and Technology)

Keywords:diurnal SST warming, boreal summer intraseasonal oscillation, Philippine Sea

The relationship between diurnal fluctuations of sea surface temperature (SST) in the Philippine Sea and the boreal summer intraseasonal oscillation (BSISO) is investigated using data of a mooed buoy deployed in the Philippine Sea at 137°E, 13°N in December 2016. Using four years of buoy data, strong diurnal cycle in SST is observed during convective suppressed phases of the BSISO, which is consistent with previous results of intraseasonal oscillations in boreal winter, called the Madden Julian Oscillation. Moreover, abrupt SST warming along with strong diurnal cycle occurred in the middle of May in both 2018 and 2019, in conjunction with the first BSISO of the year. Interestingly, the second BSISO showed no or small SST warming associated with strong diurnal cycle. In the remaining two years, 2017 and 2020, SST increased gradually with small diurnal SST amplitude, and the onset of the first BSISO was delayed. It is suggested that the abrupt SST warming associated with the strong diurnal cycle is linked to the seasonal onset of the BSISO.