Fluxes at the ocean surface are essential to the equilibrium SST. Observations of solar and longwave radiative fluxes and sensible and latent turbulent fluxes were made in-situ on six ship cruises in boreal fall along 20 S from 75-85 W, the axis of most cloudiness—and of large error in models. Solar radiation, the only warming heat flux, is 180-200 W m-2. The strongest cooling is evaporation (60-100 W m-2), followed by thermal infrared radiation (30 W m-2) and sensible heat flux (<10 W m-2).

A synthesis data set of in-situ ship observations from the southeastern tropical Pacific stratus region is publicly available. The observations summarize fluxes, clouds, aerosols, surface meteorology, and atmospheric rawinsonde profiles. Observations from the VOCALS regional experiment completed in November 2008 are presented in the multi-year context of the synthesis data set.

Observational analyses of fluxes over the oceans and fluxes from ~15 state-of-the-art coupled general circulation models used for the IPCC 4th Assessment are evaluated along the 20 S eastern Pacific ship transects. The analyses agree with ship and buoy observations, even where models have relatively large SST errors of about +2 C in October. In simulations with excessive solar heating, elevated SST results in larger evaporation compensating the solar excess.

In a long term average net annual surface fluxes are balanced by ocean advection (upwelling and horizontal transport). Analyses and simulations of fluxes thus indirectly retrieve subsurface ocean heat advection. Some models have more ocean cooling in the northern hemisphere than off the coast of Peru and Chile, with consequences for the meridional asymmetry of heating in the eastern Pacific.