Wind-driven latent heat flux and the intraseasonal oscillation

The importance of tropical west Pacific wind-driven latent heat flux anomalies for supporting boreal winter intraseasonal precipitation variability is analyzed during 1998 - 2005 using satellite and in-situ observations. Intraseasonal ( 30 - 100 day) wind speed anomalies from QuikSCAT are significantly correlated with TRMM precipitation anomalies, with instantaneous correlations peaking near 0.7 in the regions of strongest west Pacific intraseasonal precipitation variance. Positive intraseasonal wind speed anomalies occur within regions of enhanced precipitation during intraseasonal oscillation (ISO) events, suggesting an increase in the wind-driven component of latent heat flux then. Consistent with these results, west Pacific intraseasonal TAO buoy latent heat flux and TRMM precipitation anomalies are significantly correlated ( 0.5 - 0.6), and latent heat flux anomalies are primarily wind-driven. Collocated evaporation anomalies are approximately 20% of intraseasonal precipitation anomalies. Intraseasonal precipitation in the west Pacific may be supported by wind-driven surface fluxes, consistent with the modeling work of Maloney and Sobel.