Precipitation and sea-surface salinity in the tropical Pacific Ocean

Monthly sea-surface salinity (SSS) and precipitation (P) in the tropical Pacific region are examined for the 1974-1989 period. The SSS data are derived mainly from water sample measurements obtained from a ship-of-opportunity program, and the rainfall data are derived from satellite observations of outgoing longwave radiation. The mean and standard deviation patterns of SSS and P exhibit good correspondence in the heavy-rainfall regions characterising the Intertropical Convergence Zone-(ITCZ), the South Pacific Convergence Zone (SPCZ) and part of the western Pacific warm pool. An Empirical Orthogonal Function (EOF) analysis indicates two dominant modes of variation linking P and SSS changes, one mode at the seasonal timescale in both convergence zones, and the other at the ENSO timescale in the central-western equatorial Pacific (165 degrees E-160 degrees W) and in the SPCZ. The inferences derived from the EOF analysis are used in a simple linear regression model in order to try to specify P changes from known SSS changes. A comparison between hindcast and observed P changes suggests that, at seasonal and ENSO timescales, SSS changes could be used to infer the timing, but not the magnitude, of P in the central-western equatorial Pacific (165 degrees E-160 degrees W) and in the SPCZ mean area. The effects of evaporation, salt advection and mixed-layer depth on the results are discussed. Copyright (C) 1996 Elsevier Science Ltd.