Global distribution of sulfur compounds in the troposphere estimated in a height/latitude transport model

Abstract

A global two‐dimensional time‐dependent model has been used to estimate the tropospheric distributions of sulfur compounds resulting from natural emissions of H2S or DMS and from man‐made emissions of SO2. Comparisons of observations of H2S, DMS, SO2, and SO4− in remote areas with the model estimates indicate that the global flux of H2S and DMS, taken together, amounts to at most a few tens of Tg S yr−1. The present man‐made emissions Of SO2 (about 80 Tg S yr−1) can account for a dominant part of the SO2 and SO4− observed in the lower troposphere of the northern hemisphere. On the other hand, neither natural emissions of H2S and DMS at the surface nor man‐made emissions of SO2 seem to be able to explain the relatively high values of SO2 observed in the middle and upper troposphere in both hemispheres. Our calculations indicate that a relatively long‐lived precursor must be involved as a source for this SO2. The amount of SO2 produced by the oxidation of CS2 and OCS does not seem sufficiently high. Average residence times in the atmosphere for H2S, SO2, and SO4− have been estimated to about 1, 1.5, and 5 days, respectively. If only higher portions of the troposphere are considered, the residence times increase considerably.