Diurnal cycle the coupled Eta/SSiB Model for El Nino and La Nina conditions over South America

South America has a large diversity of vegetation cover which imposes substantial control on the hydrological and diurnal cycles of several meteorological quantities. This paper presents the integration and validation of the regional Eta Model coupled with the Simplified Simple Biosphere Model (SSiB). The regional atmospheric model was configured with 80-km resolution in the horizontal and 38 layers. One-month continuous integrations were performed for November 1997 (El Nino year) and November 1998 (La Nina year). NCEP analyses were used as initial and lateral boundary conditions, the latter updated every 6 hours. Observed sea surface temperature, climatological soil moisture and surface albedo were used as lower boundary conditions.

The present work focuses on the diurnal cycle of surface temperature, radiative fluxes, sensible and latent heat fluxes, and relative humidity. Four sites with different surface covers are chosen for the evaluation. The vegetation types are: (i) tropical forest; (ii) savannah; (iii) cultivation; and (iv) bare soil. A comparison of model simulated diurnal cycle amplitude with observations and NCEP analyses is shown.