Observation of Large Diurnal Warming Events in the Near-Surface Layer of the Western Equatorial Pacific Warm Pool

Alexander Soloviev*
Roger Lukas

Department of Oceanography
University of Hawaii
1000 Pope Road
Honolulu, HI 96822

31 August 1995

Because of the relatively calm winds which prevail over the western Pacific warm pool, the diurnal cycle of temperature in the near-surface layer of the ocean is often quite pronounced. During the TOGA Coupled Ocean-Atmosphere Response Experiment (COARE), very high resolution measurements of near surface thermohaline and turbulence structures were made using bow-mounted probes and a free-rising profiler. Experimental data demonstrate a strong dependence of near-surface thermal structure on weather conditions. Under calm weather conditions, SST was observed to exceed 33.2C; this was associated with a diurnal warming of more than 3C in the top 1 m of the ocean (Fig. 1). A 1D model of transilient type reproduces the strong increase of amplitude of the diurnal heating under light winds and evening deepening of the diurnal thermocline (Fig. 2). Precipitation influenced the diurnal cycle by trapping heat in the near surface region. During daytime evaporation, surface salinity slightly increased but deep convection was inhibited by the strong vertical temperature gradient. Contour plots calculated using observations from bow sensors `scanning' the upper meters of the ocean due to ship's pitching in some cases revealed structures that looked like internal waves propagating in the shallow diurnal thermocline (Fig. 3).

*permanent affiliation is the P.P.Shirshov Institute of Oceanology Russian Academy of Sciences


Soloviev, A. and R. Lukas, 1997: Observation of large diurnal warming events in the near-surface layer of the western equatorial Pacific warm pool. Deep-Sea Research I, 44, 1055-1076.

Last modified: November 3, 1997