Diurnal warming in the tropical Pacific and its interannual variability

Analyses of satellite‐derived diurnal sea surface warming of the equatorial Pacific basin from 1996 through 2000 indicate that there is, in addition to seasonal changes, an east‐west dipole. For roughly half the year, the western (eastern) Pacific experiences enhanced (decreased) diurnal warming: the opposite is true for the other six months. La Niña conditions in 1998 through 1999 affected the strength (but not the overall sign) of the dipole. Simple analyses using a comprehensive turbulent model indicate it is important to account for diurnal warming since the SST change over a day depends on the upper ocean changes due to diurnal warming. Since the tropical Pacific SST and east‐west SST gradient is of interest to ENSO processes, ocean models that do not incorporate diurnal warming may overestimate mixing‐induced cooling and the east‐west SST gradient.