The heating of the ocean surface by longwave radiation from convective clouds has been estimated using measurements from the Central Equatorial Pacific Experiment (CEPEX). The ratio of the surface longwave cloud forcing to the cloud radiative forcing on the total atmospheric column is parameterized by the f factor. The f factor is a measure of the partitioning of the cloud radiative effect between the surface and the troposphere. Estimates of the f factor have been obtained by combining simultaneous observations from ship, aircraft, and satellite instruments. The cloud forcing near the ocean surface is determined from radiometers on board the National Oceanic and Atmospheric Administration P-3 aircraft and the R/V John Vickers. The longwave cloud forcing at the top of the atmosphere has been estimated from data obtained from the Japanese Geostationary Meteorological Satellite GMS 4. A new method for estimating longwave fluxes from satellite narrowband radiances is described. The method is based upon calibrating the satellite radiances against narrowband and broadband infrared measurements from the high-altitude NASA ER-2 aircraft. The average value of f derived from the surface and satellite observations of convective clouds is 0.15¿0.02. The area-mean top-of-atmosphere longwave forcing by convective clouds in the region 10 ¿S--10 ¿N, 160 ¿E--160 ¿W is 40 W/m2 during CEPEX. These results indicate that the surface longwave forcing by convective clouds was approximately 5 W/m2 in the central equatorial Pacific and that this forcing is the smallest radiative component of the surface energy budget. ¿ 2000 American Geophysical Union