Vertical distribution of Saharan dust based on 2.5-year model predictions

Within the framework of the NASA-Israeli MEIDEX project, the averaged 3D-distribution of Saharan dust was estimated and analyzed. This averaged distribution was based on the 2.5-year database of 48-h dust forecasts produced by the dust prediction system, which had been developed earlier at the University of Athens and subsequently modified in Tel Aviv University. The performed climatological analysis is the first one based on a large archive of dust distribution over the whole Sahara and vicinity regions; the total amount of vertical profiles in this at-chive is approximately 10(7) per year. Vertical distributions of dust reflect differences between the Atlantic and the Mediterranean dust transport. As a whole, the Mediterranean dust is found to be within a wider range of altitudes, penetrating rattler higher into the troposphere. On average, dust over the Atlantic penetrates up to less than or equal to 5 km while over the Mediterranean up to less than or equal to 8 km. The characteristic feature of dust vertical profiles over the main Saharan dust source near Lake Chad is its maximal concentration near the surface. From April to June averaged profiles over the Chad basin in the Sahara are restricted below the level of similar to 4.5 km. In the winter months and in March, dust concentration over the Chad basin is closer to the surface, under 1.5 km. Dust also maximizes near the surface over another dust source, which is the major one in summer, located in West Africa. These results are consistent with dust-layer altitude ranges from present-day lidar soundings. Besides, the results are in accordance with general synoptic knowledge of the mechanism of dust transport to the Mediterranean. However, only quantitative comparisons of model vertical profiles against lidar measurements, which are under way now, call validate the forecast vertical distribution of Saharan dust. (C) 2004 Elsevier B.V. All rights reserved.