Abstract ID: 510

The Chemistry-CATT-BRAMS modeling system: numerical tools, data description and preliminary evaluation.

The CATT-BRAMS model system capability has been extended to simulate reactive gases through kinetical and photochemical reactions. The transport-chemistry model (CCATT) is an on-line system coupled to the Brazilian developments on the Regional Atmospheric model (BRAMS). The sub-grid transport parameterizations include diffusion in PBL, shallow and deep convection and plume rise for biomass burning emissions. The atmospheric model has a complex and state-of-art set of parameterizations to simulate surface-atmosphere exchanges, boundary layer development, cloud microphysics and cumulus convection. Photolysis rates are calculated on-line using FAST-JX and FAST-TUV codes and are fully coupled with the aerosol and microphysics modules. The chemistry equation system is solved using Rosenbrock methods of 2nd and 3rd orders with dynamic time-step control to keep numerical efficiency, stability and accuracy. Sequential and symmetric splitting operator has been used also to gain performance allowing the chemistry integration to use large time steps. Dry deposition is based on the resistance formulation and is coupled to the surface parameterization of the atmospheric model. Wet deposition is coupled to the cumulus precipitating parameterization. We will briefly describe the improvements that we are currently working on and that are planned in the future. We introduce preliminary results of the CCATT-BRAMS chemistry model simulations applied to the 2002 dry season in South America (SA). The model was configured with 50 km horizontal resolution covering SA. The vertical resolution starts with 150 m decreasing to 900 meters from surface to the top of the model at 20 km. Atmospheric initial and boundary conditions used the CPTEC global analysis through the 4DDA technique. The chemistry state was initialized using horizontally homogeneous data representing typical background conditions. Boundary conditions used constant inflow and variable outflow methodology. Source emissions associated with urban-industrial-transportation processes were based on RETRO/EDGAR data. Biomass burning emissions were generated with the Brazilian Biomass Burning Emission Model (3BEM) based on fire counts and instantaneous fire size obtained by remote sensing. 3BEM provided the emission intensity of several tracers, as well as information on fire size and flaming fraction required by the on-line plume rise model. Biogenic emissions are based on the GEIA inventory with an additional modulation by the solar cycle. We describe the main characteristics of simulated tropospheric ozone, NOx and carbon monoxide. We also provide a comparison of the simulated fields with data produced by the GEOS-CHEM Harvard model.

Session:  Biogeochemistry - Sources, sinks, and atmospheric chemistry of trace gases.

Presentation Type:  Poster