María I. Gassmann

A case study of biomass burning and its smoke dispersion to Buenos Aires City, Argentina

In February and March 2000, several uncontrolled forest and grassland fires occurred in the municipalities of Campana and Zarate (100 km north of Buenos Aires, Argentina). The biomass burning emitted a large amount of smoke particulates, which caused dense fog and visibility impairment in the nearby area. From 18 to 19 March, the smoke was transported towards the Buenos Aires Metropolitan Area (BAMA), resulting in a prolonged reduction of visibility. This feature was supported by a build-up of the Aerosol Optical Thickness (AOT) and deposited particulate matter mass observed in BAMA. This paper examines the prevailing meteorological situation that produced the smoke transport towards BAMA. An anticyclone, displaced easterly over the interest area by a frontal low-pressure system, produced low-level ventilation conditions that favoured the transport and the smoke persistence in BAMA. The transport of particles and the behaviour of their normalised concentrations were simulated adequately by a regional dispersion model.

BALANCE DE ENERGÍA SOBRE UN CULTIVO DE SOJA

A partir de observaciones micrometeorologicas se estudiaron los terminos de la particion energetica sobre un cultivo de soja. El desbalance observado, despreciando el calor acumulado por la cobertura vegetal, fue de 22% de la radiacion neta. Durante el periodo completo de observaciones el 60% de la energia del sistema fue utilizada para evapotranspiracion.

Photolysis rate coefficient in Buenos Aires city

The main purpose of this study was to estimate hourly meansurface photolysis rate coefficients of nitrogen dioxide for the atmospherein Buenos Aires city during cloud free conditions. A nine years periodof Aerosol Optical Depth (AOD) was used as input data to run theTUV (Tropospheric Ultraviolet Visible) model. Results showed thatmonthly maxima of surface photolysis rate doubles from winter tosummer. The study of a three month biomass burning period occurredat 70 km north from Buenos Aires City also showed an impact in thevariable studied.

A Dispersion Model Evaluation for Buoyant Releases

The application of a dispersion model of pollutants released in the atmospheric boundary is presented. Based on the bidimensional semiempirical equation, the model incorporates the current understanding of the atmospheric boundary layer dynamics to estimate and parameterize the atmospheric stability, advection, turbulent diffusion and plume rise. The model performance has previously been analyzed against experimental data obtained in non-buoyant releases with a data base covering wide parameters ranges, and showed a correct behavior1. The present evaluation involves comparisons of model estimates with measurements from studies with buoyant releases from elevated sources in flat terrain in urban areas (Indianapolis, USA) in different stability conditions2. The comparison with tracer data is done for the predicted concentrations with the proposed model (mm) and with an updated Gaussian plume model (gm). All concentrations were normalized by source strength. Only quality 3 data (Q3) have been used. The results here include urban effects on the specification of stability. Predicted normalized crosswind-integrated, maximum arcwise and centerline concentrations were compared with observations. Current quantitative measurements and techniques of model evaluation were obtained and applied3,4. The comparison was done with the full dataset and for the data stratified by stability conditions. Confidence intervals on these performance measures were determined by the bootstrap resampling procedure. The obtained statistics for the maximum arcwise concentrations are shown in Table 1.