Simulations with the coupled Eta/SSiB Model over South America

An 80-km version of the Eta Model coupled with the Simplified Simple Biosphere Model (SSiB) was used over South America to perform one-month simulations. The initial and lateral boundary conditions were taken from NCEP analyses at T62L28, for dry and wet months in South America during the 97/98 El Nino. Observed sea surface temperature, climatological soil moisture and surface albedo were used as lower boundary conditions.

Regional model simulations are compared with observations. Precipitation distribution and amplitude were well represented during both simulated months, and were consistent with observed and model OLR fields. Model precipitation was objectively evaluated in different continental regions using surface observations, and showed reasonable scores. In comparison with NCEP analyses, the simulated surface temperature patterns exhibited details associated with the increased resolution, and showed better agreement with observations. Stationary and transient water vapor flux components are estimated and compared with analyses for the dry and the wet months. A simple hydrological budget indicated that the precipitation in subtropical South America has two major contributions of water vapor: an oceanic from the Atlantic and a continental from the Amazon Basin.