Preliminary results of Coawst modeling system for Rio grande do sul state - Brazil and central region of south Atlantic ocean

Gabriel B. Münchow1,3, João Marcelo Absy2, Rita de Cássia M. Alves1, Luciano P. Pezzi2
1LMQA/CEPSRM/UFRGS - Porto Alegre - Rio Grande do Sul -
2GMO/CPTEC/INPE - São José dos Campos - São Paulo
3gabriel.munchow@ufrgs.br

Several ocean and atmospheric numerical models have been developed to improve forecasting accuracy and dynamical understanding. However, most of these models are not coupled. A two-way, coupled ocean-atmosphere-wave-sediment transport modeling system named COAWST is used and compared to an uncoupled atmospheric model. The COAWST system has ROMS as the ocean component, WRF as the atmosphere component, SWAN as the wave component, and the CSTMS as the sediment modeling component. This poster will show the preliminary results using COAWST with only WRF and ROMS. Theses models exchange Sea Surface Temperature (SST), 10m surface winds (U10m,V10m), surface atmospheric pressure (Patm), relative humidity (RH), surface air temperature (Tair), precipitation, cloud fraction, and shortwave (swrad) and longwave (lwrad) heat flux components. The experiment’s study area is from 24°S to 42°S and from 65°W to 20°W, covering the Brazilian state of Rio Grande do Sul, Uruguay, part of Argentina, and part of the south Atlantic Ocean. The ROMS grid resolution is 1/6° and WRF is 17 km. Two experiments were conducted, one with ROMS and WRF coupled (COAWST) and the other with only the atmospheric model. The simulation is from December 13th, 1979 to March 1st, 1980. The results of COAWST were compared with WRF for a frontal system that occurred on February 2nd, 1980. COAWST displayed a more intense frontal system with a more intense cyclone, higher temperature gradients, and higher fluxes of latent and sensible heat than the standalone WRF. Because of the higher resolution of the ROMS grid, more detailed patterns are captured and transmitted to the atmosphere through the sensible and latent fluxes. Thus, COAWST was able to simulate a frontal system more intense than standalone WRF. Observational data and further analysis are required to evaluate the effects of coupling against the standalone simulation. Also, it may be necessary to run simulations for longer periods.