Atmospheric humidity variations associated with westerly wind bursts during Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean Atmosphere Response Experiment (COARE)

Abstract

Precipitable water determined from special sensor microwave/imager brightness temperatures is used to examine westerly wind bursts (WWBs) in the equatorial western Pacific. Six microwave satellite water vapor retrieval algorithms are tested for their performance in the tropics. The study of two major WWB events and several localized and short‐lived wind perturbations in the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE) domain unveils the relationship between precipitable water field and anomalous wind regimes. WWBs are found to be accompanied by a drastic drop in the precipitable water amount. The decrease is partly explained by the transition between easterly and westerly wind regimes. A few days before the westerly wind is established, the transitional equatorward wind introduces the dry air from the subtropics. When the westerly wind eventually weakens, a transitional equatorward wind regime once again occurs and lasts for several days before the easterlies take over. The strongest WWB event during TOGA COARE is found to be consistent with midlatitude cold surge. This provides evidence for the midlatitude forcing of WWBs. While the interaction with higher latitudes explains the reduction in precipitable water in WWB events, it is not clear what region is responsible for feeding extra moisture to the western Pacific.