Scatterometer estimates of the tropical sea-breeze circulation near Darwin, with comparison to regional models.

In tropical coastal environments, simulating the diurnal cycle of wind and precipitation in numerical weather and climate models presents unique challenges due to the interaction of intraseasonal and mesoscale dynamics. This can lead not only to incorrect short-term weather forecasts but also to unphysical energy and momentum transport by convective processes. In particular, the sea/land-breeze circulation and its role in initiating convection has been identified as a possible source of errors in the timing and offshore extent of coastal precipitation in the Tropics. In this study, the offshore land/sea breeze around Darwin, Australia, is examined using scatterometer wind observations and two regional atmospheric models. Although the comparison is limited by satellite swath times which cluster around two times of day, useful results are obtained by sub-sampling the simulated data to match the coverage of the scatterometer data. We find that offshore surface sea-breeze characteristics (intensity and horizontal spatial extent) from the models and satellite estimates are generally in good agreement, with intensity differences less than 2 m s−1, and offshore extents not varying by more than approximately 150 km. The variation in offshore extent and amplitude of the land/sea-breeze wind perturbations with monsoon regime is well simulated. Furthermore, despite the simplifying assumptions of linear sea-breeze theory, the model and scatterometer results are in broad agreement with theoretical values, particularly in the presence of the weak background winds during the monsoon break period. [ABSTRACT FROM AUTHOR]