Search

In April 1990, forty-two scientists from eight countries attended a workshop at the Bermuda Biological Station for Research to compare field measurements with model estimates of the distribution and cycling of sulfur and nitrogen species in the North Atlantic Ocean's atmosphere. Data sets on horizontal and vertical distributions of sulfur and nitrogen species and their rates of deposition were available from ships' tracks and island stations. These data were compared with estimates produced by several climatological and event models for two case studies: (1) sulfate surface distributions and deposition and (2) nitrate surface distributions and deposition. Highlights of the conclusions of the case studies were that the measured concentrations and model results of nitrate and non-sea-salt sulfate depositions appeared to be in good agreement at some locations but in poor agreement for some months at other locations. The case studies illustrated the need for the measurement and modeling communities to interact not only to compare results but also to cooperate in improving the designs of the models and the field experiments.

Intercontinental exchange of sulphur in major parts of the northern hemisphere has been studied with a 3-dimensional Eulerian transport model that resolves regional scale variability. Model results for 1988 have been evaluated against daily observations of sulphur dioxide and particulate sulphate in Europe and North America and show that the model reproduces the episodic character of oxidised sulphur in air. Yearly averages agree with the observations within a factor of 2, at over 75% of the sites. Monthly budgets for intercontinental exchange of sulphur are presented and related to large scale atmospheric flow patterns. Intercontinental transport of sulphur is related to mid-latitude cyclone tracks, and few events determine a considerable part of the yearly intercontinental exchange. European anthropogenic sulphur dominates the averaged air concentrations and depositions over the simulation area. The contribution of European sulphur over the Sea of Japan is calculated to be 50–75 mg(S) m −2 yr −1 or 5–10% of the total deposition calculated for that area. Over the West Siberian Planes, the European contribution is estimated to be 150–200 mg(S) m −2 yr −1 that is, 40–50% of the yearly calculated deposition. The relative contributions of intercontinental transport from anthropogenic sources in Asia and North America and biogenic sources in the North Atlantic Ocean to the European deposition levels are similar and range from 2 to 4%. In certain areas and seasons, however, these relative contributions can be much larger. DOI: 10.1034/j.1600-0889.1998.t01-3-00002.x

A 3-dimensional Eulerian model is used to evaluate the influence of North American anthropogenic sulphur emissions over the western coast of Europe. Transport of sulphur across the North Atlantic ocean is simulated on the basis of the actual meteorology for 4 different months during 1982 and 1983. Results show large regional variations and indicate that the relative importance of North American emissions is largest over north western Europe. The North American contribution to pollution levels over western Europe is shown to occur mainly as wet deposition. Maximum wet deposition of North American origin over north western Europe is predicted for January 1983. On average over the four simulated months, the wet deposition of North American origin is estimated to be 2 mg S m -2 month -1 which represents 10% of the calculated total deposition over western Europe. The influence of North American sulphur on the air concentrations over the west coast of Europe is relatively larger at higher levels in the atmosphere. At ground level, the North American contribution to sulphate in air represents only 2.5% of the averaged total calculated, but it ascends to 50% at 5000 m. Maximum contributions to the sulphate concentrations in air over western Europe are estimated to occur during July 1983. DOI: 10.1034/j.1600-0889.1992.t01-1-00004.x