US EPA

5241407 

Technical Report 

Global atmospheric sulfur cycle: an evaluation of model predictions and observations 

Langner, J; Bates, TS; Charlson, RJ 

1993 

GRA and I 

e 2 

In June 1991 a workshop was held in Stockholm, Sweden, involving scientists in the IGAC (International Global Atmospheric Chemistry Project) activity MAC (Multiphase Atmospheric Chemistry) and scientists from the atmospheric chemistry group at Stockholm University. The principal goal of the workshop was to compare existing observations of DMS, SO(sub 2) and sulfate aerosol with the predictions of the global tropospheric sulfur model developed within the European research project GLOMAC (Global Modelling of Atmospheric Chemistry). The exercise has two primary aims: validating the model and evaluating the usefulness of experiments for refining this and other models. The comparisons indicate several areas where the model has to be improved. In particular, improvements in both emission estimated and description of chemical processes are necessary in order to improve the simulation of seasonal variability. Furthermore, the calculated nss sulfate concentrations in the upper troposphere are much higher than the very few available observations. If available concentrations are representative the treatment of volcanic emissions and vertical transport may have to be improved. On the measurement side the following points are made: The estimates of the emission of DMS from the oceans have to be improved. Further measurements are necessary in order to better characterize the concentration of nss sulfate in the free troposphere. The importance of sampling more than one sulfur species at the same location is stressed. 40 refs