Data from Saharan Dust Storm Reveal Model Deficiencies

McFarlane, S. A., U.S. Department of Energy

Radiation Processes

Radiative Processes

Slingo, A., T.P. Ackerman, R.P. Allan, E.I. Kassianov, S.A. McFarlane, G.J. Robinson, J.C. Barnard, M.A. Miller, J.E. Harries, J.E. Russell , S. Dewitte, 2006: Observations of the impact of a major Saharan dust storm on the Earth's radiation budget. Geophys. Res. Lett., 33, L24817, doi:10.1029/2006GL027869.


In March 2006, the ARM Mobile Facility recorded the strongest Saharan dust storm to reach the Niamey area in two years. The storm lasted several days, and visibility was reduced to 15 percent of normal.


Observations (solid lines and star symbols) and results from two models (squares, triangles) showing the amount of solar energy absorbed in the atmosphere before, during, and after the March 7-9, 2006 dust storm. During the dust storm, observations show a significant increase in atmospheric absorption while the models underestimate the amount of energy absorbed. Before and after the dust storm, the model predictions are consistent with observations.


In March 2006, the ARM Mobile Facility recorded the strongest Saharan dust storm to reach the Niamey area in two years. The storm lasted several days, and visibility was reduced to 15 percent of normal.

Observations (solid lines and star symbols) and results from two models (squares, triangles) showing the amount of solar energy absorbed in the atmosphere before, during, and after the March 7-9, 2006 dust storm. During the dust storm, observations show a significant increase in atmospheric absorption while the models underestimate the amount of energy absorbed. Before and after the dust storm, the model predictions are consistent with observations.

Saharan dust efficiently absorbs solar energy and transfers this heat to the atmosphere, which potentially alters the thermal properties of the atmosphere and affects the Earth's radiant energy budget. Recent evidence indicates that the flow of dust-laden air from Africa across the Atlantic Ocean may influence global weather patterns. Though Saharan dust storms have been observed from space, their impact on the Earth's radiation balance is poorly understood because of limited surface observations in areas affected by such storms. The study, led by Professor Tony Slingo, combines simultaneous satellite and surface observations to assess the radiant energy budget of an entire atmospheric column in the midst of a dust storm. This information is a key component in computer models that simulate both regional and global weather and climate.

The ARM Mobile Facility (AMF) was deployed in Niamey, Niger, from January through December 2006. The combination of AMF measurements at the ground with observations in space from the Geostationary Earth Radiation Budget (GERB) and Spinning Enhanced Visible and Infrared Imager instruments flown onboard the Meteosat-8 geo-stationary satellite platform provide the first well-sampled direct estimates of the divergence of solar and thermal radiation across the atmosphere. In March 2006, the AMF and satellite instruments made the first simultaneous observations of a major dust storm from space and the ground, allowing researchers to test their understanding of how dust affects the radiant energy budget of the atmospheric column.

Researchers used measurements of atmospheric temperature and humidity profiles and ground-based retrievals of aerosol optical properties—such as aerosol optical thickness and reflectivity—as input to radiation models to assess their ability to simulate the impact of the dust on solar radiation balance. The results indicate major perturbations to the energy balance at both the surface and top of the atmosphere. When compared with the satellite and ground-based observations, the models did a good job of reproducing the radiative energy balance at the surface during the dust storm, but they underestimated the solar absorption within the atmosphere, indicating that scientists need to refine their understanding of the absorbing properties of dust.

Using the entire data set from the AMF deployment in Niamey, researchers will build on this study to improve the retrievals of dust properties from the observations, perform long-term calculations of warming and cooling effects of Saharan dust, and examine the warming and cooling effects of aerosols in climate models.