The purpose of the present paper is to show the impact of implementing a convecitve trigger function in the Grell and Devenyi cumulusparameterization on the BRAMS (Brazilian developments on Regional Atmospheric Model) simulations. A dataset colected during the 1999 rainy season in the Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) project was used to evaluate the diurnal cycle of observed precipitation. The new convective trigger function is coupled to the surface sensible and latent heat fluxes. In addition, the method has the advantage of considering the average of the first 60 hPa lowest tropospheric levels to characterize the ascending pseudo adiabatically parcel. Thus, the Convective Available Potential Energy (CAPE) values are reduced delaying the maximum rainfall (although it is region dependent). A negative aspect is that precipitation is overestimation over the Andes relativelly to the original version model. It is concluded that the methodology presents advantages and disadvantages, thus evaluating other parameterizations is required, specially the soil-vegetation-atmosphere mass and energy exchabges in order to obtain more realistic simulated precipitation values over the Amazon Basin.
parameterization; diurnal cycle; CAPE
