Simulations of the Amazon Basin circulation with a regional model

Abstract

The impacts on the simulated circulation of major changes to the standard MM4 are assessed. When an improved treatment of radiative processes is included, excessive rainfall develops over the Andes Mountains and over the Amazon Basin. The excessive rainfall is concentrated in "gridpoint' storms that are not eliminated when the surface physical parameterizations are improved. Modifications to the treatment of the vertical transport of moisture are required to diminish the excessive rainfall. Even with these and other changes included in the model, the simulated basin-averaged rainfall continues to exhibit unrealistic features. The improved, though still imperfect, model simulations are used to diagnose the temporal and spatial evolution of the circulation with an emphasis on equatorial-subtropical interactions. -from Authors