Atmospheric Chemistry and Physics Discussions

Abstract. We introduce the Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS). CATT-BRAMS is an on-line transport model fully consistent with the simulated atmospheric dynamics. Emission sources from biomass burning and urban-industrial-vehicular activities for trace gases and from biomass burning aerosol particles are obtained from several published datasets and remote sensing information. The tracer and aerosol mass concentration prognostics include the effects of sub-grid scale turbulence in the planetary boundary layer, convective transport by shallow and deep moist convection, wet and dry deposition, and plume rise associated with vegetation fires in addition to the grid scale transport. The radiation parameterization takes into account the interaction between the simulated biomass burning aerosol particles and short and long wave radiation. The atmospheric model BRAMS is based on the Regional Atmospheric Modeling System (RAMS), with several improvements associated with cumulus convection representation, soil moisture initialization and surface scheme tuned for the tropics, among others. In this paper the CATT-BRAMS model is used to simulate carbon monoxide and particulate material (PM 2.5 ) surface fluxes and atmospheric transport during the 2002 LBA field campaigns, conducted during the transition from the dry to wet season in the southwest Amazon Basin. Model evaluation is addressed with comparisons between model results and near surface, radiosondes and airborne measurements performed during the field campaign, as well as remote sensing derived products. We show the matching of emissions strengths to observed carbon monoxide in the LBA campaign. A relatively good comparison to the MOPITT data, in spite of the fact that MOPITT a priori assumptions imply several difficulties, is also obtained.


Submitted on 20 Jun 2007
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Introduction
Several atmospheric pollutant transport models on regional and global scales have been proposed in the literature. Chatfield et al. (1996) use the Global-Regional Atmospheric Chemistry Event Simulator (GRACES) to introduce a conceptual model of how fire emissions and chemistry produce the African/Oceanic plumes. Grell et al. (2000) 5 describe a multiscale complex chemistry model coupled to the Penn State/NCAR nonhydrostatic mesoscale model (MM5). The Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model is an example of a global transport model. Chin et al. (2000) employed GOCART to simulate the atmospheric global sulfur cycle. Chatfield et al. (2002) present a connection between tropical emissions and an observed subtropical plume of carbon monoxide at remote areas over the Pacific Ocean, using the GRACES and MM5 models. MOZART (Model of Ozone And Related Tracers) is an "off-line" global chemical transport model appropriate for simulating the three-dimensional distribution of chemical species in the atmosphere (Brasseur et al., 1998;Horowitz et al., 2003). More recently, regional and fully coupled 15 "on-line" transport models based on atmospheric models are becoming more common; such as the Regional Atmospheric Modeling System (Freitas et al., 2005a;Wang et al., 2006) and the Weather Research & Forecasting Model (Grell et al., 2005;Fast et al., 2006), to name a few.
In this paper we describe and evaluate the Coupled Aerosol and Tracer Transport Introduction EGU in the Amazon (RaCCI) during the dry-to-wet transition season took place. The paper is organized as follows. The general characteristics of the model are described in Sect. 2 of the paper. Model configuration and a general discussion about its performance for the 2002 dry season simulation are introduced in Sect. 3. Section 4 explores model results and validation of the results based on observed data from the meteorological 5 point of view. Model results for carbon monoxide and aerosol particulate material with size diameter less than 2.5 µm are evaluated using near surface direct measurements, airborne and remote sensing retrieved data in Sect. 5. The final discussion and conclusions are reported in Sect. 6.
2 Model description 10 The model described in this paper is the CATT-BRAMS. BRAMS is based on the Regional Atmospheric Modeling System -RAMS (Walko et al., 2000) version 6 with several new functionalities and parameterizations. Throughout this text, while describing CATT-BRAMS, the original term RAMS will be used when the discussed parameterization was originally from the RAMS model, and the BRAMS term only for the aggregated 15 Brazilian developments. RAMS is a numerical model designed to simulate atmospheric circulations at many scales. RAMS solves the fully compressible non-hydrostatic equations described by Tripoli and Cotton (1982), and is equipped with a multiple grid nesting scheme which allows the model equations to be solved simultaneously on any number of two-way in- 20 teracting computational meshes of increasing spatial resolution. It has a set of state-ofart physical parameterizations appropriate to simulate processes, such as surface-air exchanges, turbulence, convection, radiation and cloud microphysics. BRAMS features include, among others, an ensemble version of a deep and shallow cumulus scheme based on the mass flux approach (Grell and Devenyi, 2002, hereafter GD)

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Planetary Boundary Layer (PBL) parameterization to modulate the maximum distance that air parcels can go up from their source level and based on that, to determine if a grid column will be able or not to sustain convection. This approach improved the simulation of Amazon basin moist convection spatial distribution as well as its temporal occurrence. BRAMS has also updated land use, soil type and normalized dif-5 ference vegetative index (NDVI) data sets. The land use map for the Amazon basin was updated with data provided by the PROVEG project (Sestini et al., 2003) while the soil type in Brazil uses data from RADAMBRASIL project (Rossato et al., 2002 Sensing Lab (tbrs.arizona.edu), converted to BRAMS data format and structure. Several biophysical parameters associated with the vegetation and soil parameterizations of RAMS were adapted for tropical and sub-tropical biomes and soils, using observations or estimations obtained in recent field campaigns, mostly associated with the LBA program.

15
CATT is a numerical system designed to simulate and study the transport and processes associated with biomass burning emissions. It is an Eulerian transport model fully coupled to BRAMS. The tracer transport simulation is made simultaneously, or "online", with the atmospheric state evolution, using exactly the same time-step as well as dynamical and physical parameterizations. EGU term (VI) is a generic sink term and refers to the dry deposition applied to gases and aerosols particles as well as the chemical transformation of CO, and, finally, term (VII) is the source term that includes the plume rise mechanism associated with the vegetations fires (Freitas et al, 2006b). The advection at grid-scale uses a forward-upstream scheme of second order (Tremback et al., 1987), and the parameterized sub-grid transport diffusion in the PBL uses the formulation contained in the RAMS model. Sub-grid convective tracer transport by shallow and deep moist convection, which is fully consistent with the respective convective parameterizations, is also taken into account. Deep and shallow convective parameterization uses an ensemble of closures and hypotheses to determine the optimal updraft mass flux at cloud base to feedback the atmospheric model, and which also controls the overall vertical tracer transport. Subgrid scale transport by downdrafts at cloud scale is also taken into account in the deep convective parameterization. Wet removal of smoke aerosol particles is associated only with deep convection, coupled to the associated cumulus scheme; see Freitas et al. (2005a) for more details. Dry deposition processes are simulated using the re-15 sistance approach, fully coupled to the RAMS surface parameterization, including the patches approach. The loss of CO by chemical transformation is included through a linearized removal with a lifetime of 30 days (Seinfeld and Pandis, 1998). Since the lifetime of CO is long, from 50 to occasionally a minimum of 15 days (Mauzerall et al., 1998), CO acts essentially as a passive tracer in the simulation. The CO in the simula-20 tions tends to flow out of the model, especially above the boundary layer, and boundary conditions control the concentration more than the linearized chemical removal. CATT is also coupled to the Brazilian Biomass Burning Emission Model (3BEM, Longo et al., 2007a), which provides on a daily basis the total amount of trace gases and aerosol particles emitted by vegetation fires, as well as the quantities needed for estimation of 25 the effective injection layer of the fraction released during the flaming phase. The data provided by the 3BEM model is used by the CATT embedded plume rise model (Freitas et al., 2006a, b) in order to determine term VII of Eq. (1). Figure 1 illustrates the main sub-grid scale processes involved in the trace EGU gas/aerosol transport and simulated by the CATT-BRAMS system. Additionally, CATT-BRAMS includes a radiation scheme that takes into account the interaction between aerosol particles and short and long wave radiation. The consistent description of the smoke and its interaction with short-and long-wave radiation make the CATT-BRAMS model reliable for atmospheric feedback studies of the smoke aerosols (Longo et al., 5 2006). BRAMS started as a software research project sponsored by the Brazilian funding agency FINEP (http://www.finep.gov.br) during 2002 and 2003. Project goals included software enhancements to achieve production quality code, maintaining research flexibility and increasing the easy to modify code characteristic. Since then, successive 10 BRAMS versions are widely used in production mode at regional and statewide weather forecast centers and in research mode for the atmospheric and environmental sciences at universities all over Brazil. Follow-on projects such as GBRAMS (Souto et al., 2007) and SegHidro (Araujo et al., 2005) disseminated BRAMS as a platform for computer sciences research (e.g. Fazenda et al., 2006). Continuous collaboration and joint 15 projects with RAMS development team maintained RAMS and BRAMS versions synchronized and kept consensus on software structure decisions over the years. BRAMS is supported and maintained by a modest software team at CPTEC that continuously transform research contributions (e.g. Freitas, 1999, Freitas et al., 2000and 2005a, Souza, 1999, Freitas et al., 2005b generated at universities and research centers into 20 production quality code to be incorporated in future code versions. BRAMS is open source software freely available at http://www.cptec.inpe.br/brams.

Model configuration and results for 2002 dry season simulation
Model simulations for the 2002 dry season were performed, and model results were compared with in-situ observations and remote sensing retrieved data. The model con-Introduction EGU mittent smoke inflow from the African fires to South America and to coordinate with and compare to the long-range transport of smoke from fires in South America to the Atlantic Ocean; and the nested finer grid with a horizontal resolution of 35 km, covering only SA. The vertical resolution for both grids varies telescopically with higher resolution at the surface (150 m) with ratio of 1.07 up to a maximum vertical resolution of 5 850 m, with the top of the model at 23 km (a total of 42 vertical levels). The soil model is composed of 7 layers with variable resolution, distributed within the first 4 m of soil depth. The total length of the time integration was 135 days, starting at on 15 July 2002 at 00:00 UTC. For the atmospheric initial and boundary conditions, the 6 hourly CPTEC T126 analysis field was used for the model initialization and to provide the necessary 10 boundary condition using the traditional RAMS scheme, the 4DDA (four-dimensional data assimilation) technique. Initial soil moisture was taken from the Gevaerd and Freitas (2006) estimation technique, with data freely available at www.cptec.inpe.br/brams on a near real time basis. The soil temperature was initialized assuming a vertically homogenously field defined by the air temperature closest to the surface from the at-15 mospheric initial data. Figure 2a shows the dominant vegetation characteristics of the regional nested grid. Figure 2b introduces the initial water content (mm) in the first 4 m of soil depth used to initialize the model soil moisture field. The horizontal distribution of the soil moisture shows strong correlation with the typical rainfall pattern during the dry season in SA, as expected: wet soils are found in the northwestern part of SA 20 accompanying the migration pathways of the convective systems; wet soils are also in the southeastern part of SA associated with precipitation of mid-latitude transient systems and, between these two regions, very dry soils in the central and northeastern parts of SA. The introduction of PROVEG data improved the representation of actual land use in the Amazon basin, and, together with the appropriate biophysical 25 parameters (i.e., the estimated initial soil moisture and leaf area index derived from MODIS NDVI data) had a strong impact on the quality of surface fluxes and PBL characteristics simulation. The vertical PBL diffusion parameterization of RAMS used in this simulation was based on the Mellor and Yamada 2.5 closure (1982)  EGU which prognoses TKE. Two tracers emitted by biomass burning were included in this model simulation: carbon monoxide (CO) and aerosol particulate material with size diameter less than 2.5 µm (PM2.5). The biomass burning sources were distributed spatially and temporally and assimilated daily using the vegetation fire locations detected by remote sensing. In this study, three sources of information on fire locations 5 and properties were used: the Wildfire Automated Biomass Burning Algorithm product (Prins et al., 1998), the Brazilian National Institute for Space Research fire product (http://www.cptec.inpe.br/queimadas), and the MODIS fire product (Giglio et al., 2003); see Longo et al. (2007a) for more details.  EGU to-day basis, several transient systems may change this mean picture, thereby altering the typical pattern of the smoke transport. The position of the SASH determines the inflow of clean maritime air into the biomass burning area, playing an important role in defining the shape of the regional smoke plume as it is the primary mechanism responsible for the dilution of the polluted air. Approaching cold frontal systems from the 5 south are responsible for disturbances in atmospheric stability and in the wind field. These changes define the main corridors of smoke export to oceanic areas. Figure 4 introduces the fraction (or the percental persistence, PP) of the total simulation time (August, September and October 2002) when the simulated aerosol optical thickness (AOT) at 500 nm channel is above 0.5. The parameter percental persistence clearly depicts the main areas heavily dominated by smoke. The accumulated number of fires per grid box observed by remote sensing in this time period and the three-months-time average wind field at 1500 m a.g.l. are also shown. Not surprisingly, the main areas disturbed by fires at the western and central part of Brazil appear with PP around 90%, which implies long term presence of high levels of air pollution, which may cause health 15 problems in the local communities and impact on weather patterns. In the Northeast Region of Brazil, in spite of the huge number of fires, the PP is relatively low due the continuous venting of clean oceanic air carried by the trade winds, besides the low amount of the available fuel load in the vegetation. The trade winds carry out pollutantladen air to the West, invading pristine areas of the Amazon basin and changing the 20 chemical composition, the cloud microphysical properties, as well as the surface and atmosphere radiation budgets. The Andes Mountains on the East side of SA, together with the SASH, impose a long range transport of smoke from its source areas to the South and Southeast of SA, thus disturbing larger areas downwind in the subtropics. The PP also shows the two major areas of inflow and outflow: to the North of the The two major biomes disturbed by fires in SA, Amazon moist forest and wooded grassland (savanna, also named "cerrado"), present remarkable differences in the Bowen ratio (B) during the dry season. Because the root distribution of Amazon trees al-5 lows water removal from deep soil layers during the dry season, there is no restriction for keeping the evapotranspiration as high as the typical values observed during the wet season (Hodnet et al., 1996). As a consequence, during the daytime the latent heat flux ( EGU responsible for the low B, as expected. The impact of the described energy budget on the afternoon PBL depth is introduced in Fig. 7. The depth of mixed layer (Z i ) at 18:00 UTC is shown and corresponds to the same time average mentioned before. Z i is lower over the oceans and in the areas affected by persistent rainfall systems. Over the Amazon basin the Z i range is from 1000 to 1500 m. Z i increases in the transitional 5 areas from forest to deforestation and cerrado areas. On the central part of Brazil, Z i peaks at approximately 2500 meters. Model basic dynamic and thermodynamic quantities were evaluated using upper air observations through radiosondes launched during the SMOCC/RaCCI campaign. At two locations in Rondônia (Brazil), Ouro Preto do Oeste (62.37 • W, 10.75 • S) and 10 Reserva Biológica do Jaru (61.91 • W, 10.14 • S), six radiosondes were daily launched daily at approximately 00:00, 06:00, 12:00, 15:00, 18:00 and 21:00 UTC, with a total of over 200 radiosondes for each location. Model air temperature, relative humidity, water vapor mixing ratio and zonal and meridional winds were compared with the respective observation data through the mean and standard deviation (STD), as shown in Fig. 8, 15 Fig. 9 and Fig. 10. Only the Ouro Preto do Oeste results are shown, since those for Jaru are very similar. Figure 11 depicts a statistical evaluation of the meteorological data available from the vertical profiling at the Ouro Preto do Oeste site. The model is warmer at the surface and moister in the lower troposphere (below 600 hPa∼4 km). The removal of the bias 20 leaves the RMS of about 2 • C for the surface temperature and between 0.5 and 1 • C for the rest of the atmosphere and 1.5 g kg −1 for the water vapor mixing ratio at low levels. Given the model grid size of 35 km and the fact that Ouro Preto lies in a small valley with topography features not resolved by the model, such differences in temperature might be expected, especially near the surface level, even after removing the bias, which 25 would only account for the difference in altitude. The low level wind speed differences are relatively small but may also be explained by the effect of local circulations, at least in the first 2-3 km, approximately. At upper levels, the unbiased RMS is relatively small compared to the standard deviation, suggesting good agreement between model EGU and observations. The moister lower troposphere is associated with a lower STD for the model results, with an unbiased RMS larger than the model STD. The values are relatively low, less than 1.5 g kg −1 ; but two reasons could account for that: the model does not include the absorption of water vapor by hygroscopic aerosol (Roberts et al, 2002); and radiosonde observations are highly variable in the lower troposphere in 5 terms of moisture, due to possible upward paths in cloudy and non cloudy areas that are not reproduced by the model, which does not resolve individual clouds. The first argument would account for a moister model and the latter for the relatively high RMS.
The model evaluation concerning the simulated total rainfall, from convective and large-scale systems, is based on the estimates provided by the Global Precipitation 10 Climatology Project "One-Degree Daily Precipitation Data Set" product (GPCP, Huffman et al., 2001). Figure 12 shows the 3-months (August, September and October) mean rainfall rate (mm day −1 ) as estimated by the GPCP product and as simulated by the CATT-BRAMS model. The model was able to consistently simulate the main patterns of the rainfall, but with some disagreement in terms of the mean rate. The 15 ITCZ over the ocean appears with a lower rainfall rate, while over land it is higher compared to the GPCP retrieval. In the Southern region of Brazil and over the Atlantic Ocean, the model also simulates weaker rainfall rates. However, rainfall retrievals from satellite also present limitations. For example, underestimation of precipitation rates associated with clouds with low top height in the Amazon basin, and overestimation 20 associated with rain falling in dry environments with consequent re-evaporation, like in Southern Brazil and Northern Argentina.
Note also that if we have faith in the observations, the GD scheme may be statistically trained with observations to weight the ensembles that are used to determine the location and strength of the convection. This is especially the case if a systematic 25 behavior of any of the closures can be identified. However, for our runs, not statistical training methods were used yet. Introduction EGU 5 Model PM2.5 and CO results and comparison with observed data

Model evaluation with SMOCC/RaCCI 2002 surface and airborne measurements
In this section, we present model results for tracers on the regional grid with 35 km resolution, as stated above. CO and PM2.5 near-surface measurements were made at the Ouro Preto do Oeste pasture site, during the SMOCC/RaCCI field campaign from 10 EGU fires. In Rondônia state, fires were rare but there were a few hot spots still observed in the region. By the end of October, the onset of the wet season drastically reduced the number of fire counts everywhere in South America. This pattern is clearly reflected in the surface-level CO and PM2.5 measurements performed in Rondônia and also in the model results. For both periods, the model agreements are fairly good.

5
Comparison of simulated CO profiles in the PBL and lower troposphere with observed data were performed using SMOCC/RaCCI campaign airborne measurements (Andreae et al., 2004). The airborne component of SMOCC/RaCCI took place in the Amazon Basin during September and October of 2002. Carbon monoxide (CO) measurements during SMOCC/RaCCI were obtained onboard the INPE Bandeirante aircraft using an Aero-Laser (AL5002) instrument operating at 1 Hz. The typical maximum altitude reached by the SMOCC/RaCCI aircraft was 5 km. The measurement accuracy is better than ±5%; details can be found in Guyon et al. (2005). Figure 14 shows comparisons for sixteen flights. The mean and STD of the observed CO profiles are shown; note that STD represents the actual variability of the concentrations, not the 15 measurement error.
The flights considered in this study took place over the state of Rondônia and North of Mato Grosso, one of the areas with the highest occurrence of vegetation fires in the Amazon basin. With fire spots widespread in the experimental area, the smoke spatial and vertical distribution was strongly inhomogeneous, as shown by the STD 20 of the mean observations taken for the same model vertical layers. Very often the climbing and descending profiles show large differences, revealing the inhomogeneity of the aerosol concentration either due to the presence of isolated smoke plumes or very thin smoke layers detrained from convective systems and fire plume rise. As expected, the model resolution of 35 km did not allow the point-by-point reproduction of 25 the effect of sub-grid phenomena in the profiling. Nevertheless, it very well succeeded in representing the mean pattern of each airborne profile, with the model results almost always falling within the STD of the observations. The overall model performance can be evaluated in Fig. 15 EGU presented together with the mean CO model. The model result is very consistent with the observed mean, being always inside of the STD range. Figure 15 also indicates that the model is able to accurately capture the vertical distribution of the observed concentrations.
It is important to emphasize the difficulty for an "on-line" and coupled model to sim-5 ulate observed profiles such as those associated with biomass burning, in view of the non-linearities of the processes and the uncertainties in estimating the emission sources. Among the relevant uncertainties are: the realistic representation of the radiative transfer in the presence of aerosols, the adequate representation of water and heat surface fluxes that are strongly controlled by the soil moisture content and the PBL 10 evolution, as well as an appropriate spatial and temporal distribution of the emission source strength, including the plume rise mechanism. Also important is the appropriate definition of the regional boundary inflow and outflow through advective transport.

Model comparisons with MOPITT data
Model performance on larger scales and including upper tropospheric levels is evalu-15 ated in this section, using data retrieved by the "Measurements of Pollution in the Troposphere" (MOPITT) instrument, onboard the Earth Observing System Terra satellite. MOPITT retrievals of tropospheric CO mixing ratio (ppb) are reported for 7 pressure levels, from the surface to 150 hPa (Deeter et al., 2003). Because MOPITT data have large horizontal areas without valid data due to swath width and cloud cover, the model 20 results, after applying the averaging kernel and a priori profile, and using retrievals with < 50% a priori contribution, and MOPITT data were monthly averaged. Figure 16 shows the comparisons for the months August, September and October on five vertical levels (850, 700, 500, 350 and 250 hPa) at the large scale grid. The quantity depicted in the above-mentioned figure is the relative model error (ME) defined as

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where CO model is the monthly mean of model CO mixing ratio after applying the averaging kernel and a priori fraction <50%. According to the above definition, positive values mean that model results are underestimated in reference to the MOPITT retrieved data and vice-versa. August is one of the driest months with few cases of convective systems over SA. Therefore ME is small and within a range of 10% above 500 hPa 5 (Figs. 16a, b andc ). Below 500 hPa (Figs. 16d and e) and on the central and north part of SA, ME is within a range of less than 20%, with only few places with larger errors. Southward 30 • S, ME presents higher absolute values mainly in the lower levels. However, in this region it is very difficult to assess the model performance because, since it is not usually affected by the biomass burning emissions in SA, the concen-10 tration of tracers is mostly determined by the lateral boundary condition at the model eastern border. Additionally, MOPITT retrievals are less reliable in low levels due to the typically stronger influence of the assumed a priori for retrieved surface level CO concentration than for higher levels (Deeter et al., 2003). The very noticeable north-tosouth variations in ME, especially at 850 and 700 hPa are due to a well known aspect 15 of the MOPITT method. The MOPITT algorithm was designed to have very simple a-priori assumptions. Aircraft observations suggest that lower tropospheric CO is relatively high with respect to the tropospheric CO profile in the Northern Hemisphere, and relatively low in the Southern Hemisphere. MOPPITT has relatively more information and does not require a-priori assumptions over certain types of land areas. These ob-20 servations help explain the north-south trend in the ME and the fact that the trend is most evident over ocean regions (Deeter et al., 2007). Over Africa, the model has its worst performance, which is mainly due to the relatively poor emission estimates for this continent. For the African continent only the MODIS fire product was considered.
From September to October the number of convective systems increases over SA 25 and this fact is reflected in Figs. 16f, g, h, l, m and n. There is much more CO above 500 hPa over SA with a clear outflow to the Atlantic Ocean following the westerly jets.
The ME over SA is again within a range of less than 20%, with only few places with 30% or larger error. Over the Atlantic Ocean, ME is mostly less than 30%, which EGU demonstrates the validity of the numerical results of the model, mainly a result of the improved deep moist convective and plume rise parameterizations. Below 500 hPa (Figs. 16i,j,o and p) and over SA, the model performs satisfactorily as well, with the reasons for larger errors south of 30 • S and on low levels already discussed. In summary, where the MOPITT data is most reliable, ME is less than 30% in absolute 5 value.

Examples of the model performance from daily-scale cases studies
Model performance on larger scales and on a daily basis is evaluated in this section through two select cases. 10 We revisit the 7 to 9 September 2002 cold front convective case already discussed by Freitas et al. (2005a), where the model simulation of the effects of a mid-latitude cold front on smoke and CO transport and distribution is described. The role of this transient system on the horizontal and vertical re-distribution of aged smoke in the PBL is discussed as well as the associated wet removal of aerosol particles. Here 15 we evaluate the convective transport of CO, mostly associated with deep and moist convective systems, using the MOPITT data already introduced. Figure 17 presents the model CO mixing ratio (on the left) and the model error (ME) relative to the MOPITT CO retrievals (on the right), after applying the averaging kernel and a priori fraction <50%, at 500, 350 and 250 hPa. As before, because the valid MOPITT data are sparse, 20 model and MOPITT data were time averaged over the days 6, 7, 8 and 9 September, approximately the duration of the cold front system event. Figure 17a  EGU the ME at the same pressure level over both areas, continental and oceanic. The ME is less than 20%, denoting combined good skill of the model and satellite retrievals. The levels 350 (Fig. 17c) and 500 hPa (Fig. 17e) present stronger CO enhancement, with transport mostly to the East (by the westerly jest) and to the West (by the trade winds), respectively. The correspondent model performances are shown in Figs. 17d 5 and f. Again the ME is mostly in between ±20%. Longo et al. (2006) showed a continental river of smoke crossing the east side of the Andes Mountains on 27 August 2002. This smoke transport was detected by MODIS and was associated with an event of Andes low level jets (Vera et al., 2006). Fig-10 ure 18a shows the river of smoke in terms of the MODIS aerosol column (mg m −2 ) retrieval (Remer et al., 2006). In spite of the existence of extensive white areas without valid data, mainly due to cloud contamination, the continental-scale smoke plume traveling from the Amazon basin area to the southern part of SA and exiting towards the South Atlantic Ocean following the circulation ahead of an approaching cold front 15 (not shown) can be envisioned. Model results as a composite of the regional and large scale grids are show at Fig. 18b. The patterns of the continental-scale smoke plume are clear in this image and depict the smoke inflow areas from Africa, the outflow to the South Atlantic Ocean, as well as the emission sources from biomass burning regions. Also the modeled smoke pattern resembles very well the MODIS-retrieved pattern and 20 indicates that the model dynamics work properly. Also this comparison highlights the usefulness of a highly time-and space-resolved, fire-location based emission model (Longo et al., 2007a) because the modeled smoke is then spatially and temporally injected into the atmosphere only where and when fires actually took place. We do not show a statistical analysis between the MODIS aerosol product and model simulation 25 for this case; however, a quantitative visual comparison between the two results can be done from Fig. 18 and shows a high degree of model skill. A description and evaluation of the CATT-BRAMS model is provided in this paper. CATT-BRAMS was primarily designed to study the surface fluxes and atmospheric transport of biomass burning emissions in South America. This model system has proven to be very useful for the understanding and prediction of the typical controls of 5 synoptic systems on the transport and dispersion of pollutants from biomass burning. CATT-BRAMS shows a strong ability to reproduce realistically the horizontal distribution of passive tracers and aerosol particles on a regional scale. The fine skills for predicting the vertical tracer distribution also indicate the reliability of the CATT-BRAMS model's sub-grid transport processes parameterizations. Following the validation for the atmo-10 spheric transport of passive tracers, a chemical mechanism is being coupled to this system model, providing a more complete system that will be able to prognose also reactive chemical species, such as the tropospheric ozone produced from precursors emitted by the vegetation fires in SA.

ACPD
It is important to emphasize that the successful compromise between model detail 15 and computational cost achieved in CATT-BRAMS has made possible the operational application of this system for daily numerical air quality monitoring and forecasting over SA, associated with smoke emission from vegetation fires, since 2001. Operational products are available on a daily basis at http://www.cptec.inpe.br/meio ambiente, and have been widely used for several purposes that go from scientific to public health 20 applications (e.g., Andreae et al., 2004;Cordova et al., 2004;Marécal et al., 2006a, b;Fernandes et al., 2006;Gevaerd et al., 2006;Ramos et al., 2006;Brazil  Prins, E., Santos, J. C., Gielow R., and Carvalho Jr., J. A.: Including the sub-grid scale plume rise of vegetation fires in low resolution atmospheric transport models, Atmos. Chem.