Efeito da vegetação em simulações numéricas com o modelo RAMS.

Abstract

The atmospheric model Regional Atmospheric Modeling System (RAMS) is used in order to analyze the influence of the vegetation coverage on the configuration of surface parameters. The leaf area index (LAI) and the vegetation fraction (Vfrac) were estimated from bi-weekly data of normalized difference vegetation index (NDVI) obtained from images of the satellite AVHRR/NOAA reduced to a grid of 5.5 by 5.5 km2. The region studied was Northeast Brazil, for April of 1983 and 1986. The estimated parameters were introduced into RAMS and five-day simulations were performed to evaluate their impact. Since the estimated values of LAI and Vfrac were smaller than those tabulated in RAMS, an increase in sensible heat flux and a decrease in latent heat flux were observed. The atmosphere became warmer and dryer in the turbulent boundary layer. The amount of solar radiation reaching the ground was not affected. On the other hand, the long wave radiation emitted increased in view of the surface temperature increase. Although evapotranspiration decreased, convcctivc precipitation was enhanced along the simulation. Analysis for each homogeneous region showed that the greatest impact occurs in Caatinga.