Diurnal cycle of precipitation in the Tropics

The diurnal cycle is one of the most prominent periodic phenomena in our climate system. During the warm season in monsoon regions, diurnal characteristics have significant impacts on the local climate, since the total precipitation amounts depend on the intensity of the diurnal cycle.

Diagnosis of the simulation based on a global atmospheric GCM with a spatial resolution of about 50 km indicates that the model is capable of replicating many details of the diurnal cycle of precipitation over the principal monsoon regions, such as the Indian Subcontinent, Indo-China Peninsula, Indonesian Archipelago, Central America, and equatorial Africa. The regional details bear intimate relationships with the geometry of the local coastline and orographic terrain.

This study also reveals strong propagating diurnal signals over the Bay of Bengal and South China Sea, which are situated downwind of land masses with strong daytime convective activities.

The model results have been compared in detail with satellite data with comparable spatial resolution. Such analyses are helpful for identifying strengths and weaknesses of the GCM in mimicking various physical processes contributing to the diurnal cycle of precipitation.