The MSA:nss SO4= ratio, which is a measure of the
relative marine biogenic contribution to the total atmospheric sulphur
burden, has long been measured in various parts of the globe. Transect
studies and observations from a network of stations have provided some
idea of the spatial and temporal behavior of the ratio in various
regions, but gaps in knowledge still exist in other parts of the globe.
Here we present results of a global 3-D chemical transport modeling
study which complement these measurements and provide a globe-wide
picture of the spatial variation and distribution of this ratio.
Comparison of modeled versus measured data on the MSA:nss
SO4= ratio resulting from all sulphur sources
considered shows fair model performance (i.e., a general overestimation
of 23%; degrees of freedom = 90) in all areas of the globe where actual
measurements of the ratio have been made. On the other hand, the
model-observation comparisons for the MSA:nss SO4=
ratio derived solely from the oceanic DMS source are not as satisfactory
(an overall overestimation of a factor of 3; degrees of freedom = 50).
The MSA:nss SO4= ratio that is derived from the
oceanic DMS source alone provides information on the relative yields of
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