Mineral dust is a major component of aerosols over large areas of the Earth. Dust from arid regions can be carried thousands of kilometers, even on intercontinental scales. For this reason there has been an exponential increase in scientific publications related to dust-modeling and its effects on atmospheric radiation, ozone photochemistry, human health, and ocean bio-geochemistry. Our paper presented a new concept for modeling dust sources on a global scale and it made detailed comparisons between model results and observations. The paper now serves as a standard for model comparison. Also, it provides useful information on dust characteristics important for understanding dust’s effects on the Earth's ecosystems and for anticipating the impacts of climate change on these various processes.

The paper provides a new picture of the global distribution of dust sources; these are shown to yield a more realistic dust distribution. The paper also presents a new methodology to analyze the characteristics of global dust distributions in detail by comparing model results with ground-based aerosol measurements and satellite aerosol products. Our model yields dust concentrations that compare favorably with the day-to-day variability measured at many locations on the globe.

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A major fraction of the mineral dust aerosol in the atmosphere is emitted from preferential sources located in topographic depressions in arid regions where alluvium has accumulated. When the soil is dry, winds can lift silt and clay particles forming the alluvium and transport the particles for thousands of kilometers, producing large dust-plumes readily seen in satellite images. By absorbing and scattering solar radiation, dust particles affect the atmospheric radiative budget as well as the photochemical production of tropospheric ozone. When the dust is finally removed from the atmosphere, over a period of days or a few weeks, it is deposited onto land or ocean surfaces where it can provide essential nutrients for a wide range of ecosystems. Today, for instance, a major research effort is focused on understanding the role of dust-borne iron on marine ecosystems in iron-depleted open oceans. It is believed that the global carbon cycle can be significantly modulated by the varying input of wind-borne dust to the global oceans. Our model will be useful in understanding how climate change will affect dust generation and the subsequent impact on the global carbon cycle. Changes in dust emissions with climate could also have a feedback on climate-forcing processes, further complicating the problem of anticipating the effects of climate change.

Paul Ginoux's involvement in dust-modeling started with post-doctoral research at NASA, working closely with scientists of the Total Ozone Mapping Spectrometer (TOMS) Science team. Although TOMS was designed to measure column ozone on a global scale, it was found to respond to the presence of aerosols as well. It is particularly sensitive to solar-radiation absorbing aerosols such as mineral dust. The ultimate objective of the TOMS aerosol program was to develop a global dust model in order to study the radiative impact of dust and to improve the quality of ozone retrievals from the TOMS satellite. Because of the success of the model and the TOMS aerosol product, they have become important tools in climate research in general.

Joseph Prospero's research with dust began almost 40 years ago as a result of his interest in the impact of continental aerosol sources on the composition and physical properties of particles in the marine atmosphere. He was also interested in the role of wind-transported dust in the formation of deep-sea sediments.

Ginoux and Prospero had a common interest in trying to understand the environmental factors that affected the generation and transport of dust. This knowledge is important not only to improve our understanding of the role of dust in present-day climate forcing but also in helping us to understand how dust generation might be affected by climate change. We noticed from the TOMS aerosol data that, contrary to the assumption of existing models, all desert areas do not emit dust in a uniformly consistent manner, that is, as a function of soil properties, soil moisture, wind speeds, etc. Instead, we found that most emissions originate from topographic depressions in arid regions. We also found that almost all the major dust sources are located in regions that were flooded in geologically-recent times, during the past 20,000 years or so. This aspect of our research is presented in a companion paper: Prospero, J.M., P. Ginoux, O. Torres, S. Nicholson, and T. Gill. Environmental characterization of global sources of atmospheric soil dust identified with the NIMBUS 7 Total Ozone Mapping Spectrometer (TOMS) absorbing aerosol product. Rev. Geophys. 10.1029/2000RG000095, 04 September 2002.

Using TOMS data and the model we developed a new source inventory which provided a more realistic dust distribution than before even on a day-to-day basis. Our new inventory was then used for scenarios in the recent report of the Intergovernmental Panel on Climate Change (IPCC)—IPCC, 2001: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, [Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson, Eds.] University Press, Cambridge, United Kingdom and New York, NY, USA, 881pp.

This gave our research international recognition. The general approach used in our model is now incorporated in many dust models around the world. Variations of our source model are used for making dust forecasts including those used during the recent Iraq invasion.