Impact of Precipitation Assimilation on Climate Simulations over Brazil
Ana
Nunes, ECPC/SIO/UCSD, anunes@ucsd.edu
(Presenting)
John
Roads, ECPC/SIO/UCSD, jroads@ucsd.edu
Masao
Kanamitsu, ECPC/SIO/UCSD, mkanamitsu@ucsd.edu
Although atmospheric analyses and reanalyses are now providing physical realistic fields for many variables, precipitation remains problematic. This study describes the implementation of an initialization procedure, which allows assimilation of precipitation by the Regional Spectral Model (RSM) and improves related hydroclimatological simulation skills as well. We currently nudge atmospheric moisture, since the atmospheric humidity adjustment leads to stable temperature and wind changes and the RSM precipitation then remains close to the observed precipitation. Experiments nudging the atmospheric heating are also being developed to determine if further improvements can be made. In particular, RSM simulations over Brazil, during the rainfall season of the Amazon region and increased activity of the South America Convergence Zone, forced only by the large-scale global analysis are being compared to simulations that also incorporate precipitation assimilation into Simplified and Relaxed Arakawa-Schubert convection schemes. Additional long-range forecast skill may result from coupled interactions of a more realistic precipitation with the RSM land surface, which may thus be better initialized by this procedure than it is currently initialized by the global analyses.