Interannual moisture variations near the surface of the tropical Pacific Ocean

Interannual variations of surface specific humidity, surface latent heat flux out of the ocean and surface layer moisture divergence are analysed for the period 1957–76. Special emphasis is given to understanding the relationship between variations in these quantities and the El Niño/Southern Oscillation phenomenon. The analyses include eigenvectors, composites and time series. The results indicate spatially coherent temporally persistent variations, some of which are clearly linked to El Nino. The composite and time series analyses both suggest that during El Niño in the eastern Pacific moisture convergence changes precede those of sea surface temperature by one or more months, which in turn precede those of surface latent heat flux by a further one or more months. A hypothesis is suggested to relate these changes to variations of the South Pacific high.