Diurnal Cycle of Surface Winds in the Maritime Continent Observed through Satellite Scatterometry

Abstract

AbstractThe diurnal cycle of surface winds throughout the Maritime Continent plays a significant role in the formation of precipitation over the islands of the region and over the surrounding seas. This study investigates the connection between the diurnal cycles of surface wind and offshore precipitation using data from four satellite scatterometer instruments and two satellite precipitation radar instruments. For the first time, data from three scatterometer instruments are combined to yield a more temporally complete picture of the surface wind diurnal cycles over the Maritime Continent?s surrounding seas. The results indicate that land?sea breezes typically propagate over 400 km offshore, produce mean wind perturbations of between 1 and 5 m s?1, and propagate as gravity waves at 25?30 m s?1. Diurnal precipitation cycles are affected through gravity wave propagation processes associated with the land?sea breezes, and through the convergence of land breezes from nearby islands. These observational results are then compared with previous mesoscale modeling results. It is shown that land?sea breezes occur too early, and are too intense in these modeling results, and this may partly explain why these modeling results also exhibit an early, overly intense diurnal precipitation cycle. This study also investigates variations in the diurnal cycle of surface winds at seasonal and intraseasonal time scales. Previous work has suggested that seasonal and intraseasonal variations in surface heating affect the land?sea breeze circulation and diurnal precipitation cycles; we argue that variations in background winds also play a defining role in modulating coastally influenced local winds.