Research brief: How sea surface temperature changes daily in Tropical Warm Pool

Five year (2010–2014) Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature (SST) data produced by the Australian Bureau of Meteorology has been validated against drifting buoy data and then used to study the seasonal patterns of the sea surface temperature daily variation (DV) events over the Tropical Warm Pool region (TWP, 25°S–15°N, 90°E–170°E).

The drifting buoy validation results illustrate the overall good quality of the AVHRR SST data set, although an average 0.19 K underestimation of the daytime measurements was observed.

The nighttime observations are in good agreement with in situ buoys with an average bias of 0.03 and a 0.30 K standard deviation of the biases.

This sea surface temperature data set was then used to characterize the SST DV seasonal patterns, together with wind speeds, daily maximum solar shortwave insolation (SSImax), and latent heat flux (LHF).

A double-peak seasonal pattern of SST DV is observed over the study region: the strongest DVs are found in March and October and the weakest in June.

Sensitivity tests of DV to wind, SSImax, and LHF were then conducted. The results indicate:

  1. Different morning and early afternoon winds (7 A.M. to 2 P.M. local time, LT) affect DV by as much as 0.73 K when the half-daily (defined as 2 A.M. to 2 P.M. LT in this study) average winds are fixed between 2 and 3 m s−1;
  2. SSImax levels regulate DV less significantly (<0.68 K) under fixed winds; and (3) LHF effects on DV are relatively weak (<0.35 K).

 

Paper: Seasonal patterns of SST diurnal variation over the Tropical Warm Pool region
Photo (top left): Hateruma 2013 by Kobaken

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