Regime-Dependent Differences in Surface Freshwater Exchange Estimates Over the Ocean

Differences in gridded precipitation (P), surface evaporation (E), and the resultant surface freshwater exchange (P − E) among different products over the ocean are diagnosed as functions of moisture advection (Q_advt) and moisture tendency by dynamical convergence (Q_cnvg). Compared to the GPCP product, the TRMM3B42 product captures higher frequency of precipitation with larger extreme precipitation rates in regimes of deep convection and more light rain detections in regimes of frequent occurrence of boundary layer clouds. Discrepancies in E depend on moisture flux divergence, with the OAFlux product having the largest E in regimes of divergence. Discrepancies in mean P − E in deep convective regimes are highly influenced by differences in precipitation, with the TRMM3B42 product yielding P − E histograms closer to those inferred from the reanalysis moisture flux convergence. In nonconvergent regimes, observation-based P − E histograms skew toward positive values while the inferred reanalysis histograms are symmetric about the means.