Model Calculations of Sulfate Column Burden over the North Atlantic and Adjacent Continental Regions

Click on the following image icon to see a single frame of the animation, representing the sulfate column burden for the North Atlantic and surrounding continental regions for UT 00:00, April 5, 1987.

Click on the following animation icons to see the entire animation. The animations contain depicitions of the column burden from June 28, 1986 to July 31, 1986 (860628 to 860731), from October 13, 1986 to November 15, 1986 (861013 to 861115), from January 21 to February 28, 1987 (870121 to 870228), and from March 21 to April 30, 1987 (870321 to 870430). The files are in Quicktime (R) format and are between 6 and 9 MBytes. They can be viewed with your usual helper application for Quicktime documents. Playback speed is 4 frames a second. Note: 4 frames represent one day of model time. To be fully appreciated each movie should be played as a repeating loop.

Jun-Jul 86 Oct-Nov 86

Jan-Feb 87 Mar-Apr 87

A few words about the simulations: Sulfate concentrations are calculated with a chemical transport and transformation model that is driven by observation-derived meteorological data, specifically the 6-hour forecast fields calculated by the European Center for Medium Range Weather Forecasts (ECMWF). Emissions include anthropogenic and natural SO2, non-seasalt sulfate, and reduced sulfur gases (mainly dimethylsulfide, DMS). Chemical transformation includes clear-air and in-cloud oxidation of SO2 and clear-air oxidation of DMS. Material is removed by wet and dry deposition. The model domain extends from -140 to +62.5 Degrees longitude (west of North America, across North America, the North Atlantic, and Europe, to the Urals) and has 1.125 Degree resolution. There are 15 levels in the vertical extending from the surface to about 100 hPa (the model uses ECMWF "eta" coordinates to conserve mass). Column burdens depicted here are evaluated as the vertical integral of concentration.

The animation does an excellent job of capturing the richness of the model output. Attention is called first to the high spatial variability of the column burdens; note that to capture the large dynamic range of the column burdens a logarithmic scale is employed, covering three orders of magnitude. Next note the high temporal variability. It is possible to see material building up in emissions regions (North America, Europe) and transported by the wind fields. Numerous circulations can be observed over several day periods under the influence of high or low pressure systems.

A few words about the Jun-Jul 86 simulation. Note especially that values of the column burdens are the highest of all simulations, especially over high emissions areas, the transport from North America does not influence the subtropics, the influence from Central European emissions on Scandinavia coming directly from the south. On June 9 and following days the transport from North America bifurcated over the northeast Atlantic. Starting on July 28, a large North American plume reached Europe.

A few words about the Oct-Nov 86 simulation. Note especially the circulation patterns around Europe, the west circulation from Africa to the West Indies, the transport from North America in a large wave heading first southeast, then turning northeast at approximately 50W, 20N, and turning southeast again at approximately 30W, 50N to influence the Iberian peninsula. Also note that depending on the prevailing winds, the plume from Mexico City can directly influence either the western Pacific (around Oct 15) or the Gulf of Mexico (around Nov 11).

A few words about the Jan-Feb 87 simulation. Note especially the much lower column burdens over the whole domain, the transport from eastern North America southeast then northeast across the Atlantic starting on Feb 21, the transport from Europe north and circulation around Scandinavia on Feb 8, the transport from Europe southeast over the Mediterranean, the Middle East and North Africa (Feb 27-28), the circulation around low pressure systems in the North Atlantic starting Jan 31.

A few words about the Mar-Apr simulation. Note especially the transport of Northern European emissions out over the eastern Atlantic under influence of a low pressure system April 4-7. Note also the build up and circulation of sulfate over eastern North America under high pressure on April 10-14. Note also build up and trapping of material in a low pressure system centered on the Carolinas on April 16-18. Finally note an instance of rapid transport of North American sulfate across the North Atlantic and toward Spain on April 24-26. These calculations suggest that the North Atlantic column burden of sulfate is dominated by contributions from industrial regions in the neighboring continents.

The March-April simulation is analyzed in detail in an electronic publication (Benkovitz et al., 2001) that focuses on the role of particular meteorological situations, especially cut-off low pressure systems, in conjunction with the location of emissions, in generating episodes of high sulfate concentration.

The model is fully described in Benkovitz et al. (1994), which presents a few (static) results for a one-month simulation during fall 1986, comparisons with observations, and various statistics characterizing the model output. Benkovitz and Schwartz (1997) presents additional comparisons with observations and statistics on those comparisons.


Benkovitz C. M., Berkowitz C. M., Easter R. C., Nemesure S., Wagener R. and Schwartz S. E. (1994) Sulfate over the North Atlantic and adjacent continental regions: Evaluation for October and November 1986 using a three-dimensional model driven by observation-derived meteorology. J. Geophys. Res. 99, 20725-20756.

Benkovitz C. M. and Schwartz S. E. Evaluation of Modeled Sulfate and SO2 over North America and Europe for Four Seasonal Months in 1986-87. J. Geophys. Res. 102, 25305-25338, 1997. (Electronic version: 6 Mbyte PDF file)

Benkovitz C. M., Miller M. A., Schwartz S. E. and Kwon O-U. Dynamical influences on the distribution and loading of SO2 and sulfate over North America, the North Atlantic and Europe in April 1987. Geochem. Geophys. Geosyst. 2, Paper no. 2000GC000129 (2001).

For a reprint, send email to Carmen Benkovitz or Stephen Schwartz

This page was last updated 2002-12-17.


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