TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 64 (No. 6), pp. 847-857, 2008

In-situ Diurnal Sea Surface Temperature Variations and Near-Surface Thermal Structure in the Tropical Hot Event of the Indo-Pacific Warm Pool

Hiroshi Kawamura1*, Huiling Qin1 and Kentaro Ando2

1Center for Atmosphere and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
2Japan Agency of Marine-Earth Science and Technology, Yokosuka 237-0061, Japan

(Received 31 July 2007; in revised form 20 April 2008; accepted 28 April 2008)

Abstract: Diurnal Sea Surface Temperature (SST) variations and the near-surface thermal structure of the tropical hot event (HE) have been investigated using advanced in-situ equatorial observations with hourly temporal resolution. The information on the HE area defined by the satellite cloud-free SSTs is used to sample the in-situ observations. The in-situ SSTs sampled for the HE conditions show that a maximum (minimum) SST has a histogram mode at 30.8°C (29.0°C), and frequently appears at 15:00 (07:00) local time. The amplitude of the diurnal SST variation (DSST) is defined by the difference between the maximum and minimum SSTs. The mean DSST during HEs is greater than 0.5°C, and has a maximum of about 0.75°C at the HE peak. The time series of mean DSST gradually increases (rapidly decreases) before (after) the peak. The satellite SST has a systematic positive bias against the corresponding daytime SST measured by the Triangle Trans-Ocean buoy Network. This bias is enhanced under conditions of large in-situ DSST. One-dimensional numerical model simulation suggests that the systematic bias is caused by the sharp vertical temperature gradient in the surface layer of HE. The near-surface thermal structure is generated by conditions of high insolation and low wind speed, which is the typical HE condition.

*Corresponding author E-mail: kamu@ocean.caos.tohoku.ac.jp

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