Dust altitude and infrared optical depth from AIRS C. Pierangelo, A. Chédin, S. Heilliette, N. Jacquinet-Husson, and R. Armante Laboratoire de Météorologie Dynamique/Institut Pierre Simon Laplace, Ecole Polytechnique, Palaiseau, France
Abstract. We show that mineral dust optical depth and altitude can be retrieved from the Aqua -
Advanced Infrared Radiation Sounder (AIRS) measurements. Sensitivity studies
performed with a high spectral resolution radiative transfer code show that dust
effect on brightness temperatures may reach about 10 Kelvins for some channels.
Using a Look-Up-Table approach, we retrieve not only the 10 µm optical depth but also the altitude
of Saharan dust layer, above the Atlantic Ocean, from April to September 2003.
A key point of
our method is its ability to retrieve dust altitude from satellite observations.
The time and space distribution of the optical depth is in good agreement with
the Moderate resolution Imaging Spectroradiometer (MODIS) products. Comparing
MODIS and AIRS aerosol optical depths, we find that the ratio between infrared
and visible optical depths decreases during transport from 0.35 to 0.22,
revealing a loss in coarse particles caused by gravitational settling. The evolution of
dust altitude from spring to summer is in agreement with current knowledge on transport seasonality.
Citation: Pierangelo, C., Chédin, A., Heilliette, S., Jacquinet-Husson, N., and Armante, R.: Dust altitude and infrared optical depth from AIRS, Atmos. Chem. Phys., 4, 1813-1822, doi:10.5194/acp-4-1813-2004, 2004.