11th Conference on Atmospheric Radiation and the 11th Conference on Cloud Physics

Monday, 3 June 2002
Aerosol and radiation studies with the UK Met Office C-130 aircraft during the SaHAran Dust Experiment (SHADE).
Jim M. Haywood, Met Office, Farnborough, Hants,, United Kingdom; and E. Highwood, M. Silverstone, S. Newman, D. Tanre, and J. Pelon
The Met Office C-130 and the French Mystere aircraft were based in Sal, Cape Verde Islands during the period September 19-28, 2000. During this period a large Saharan Dust storm was observed off the coast of W. Africa. The C-130 was equipped with standard meteorological equipment, aerosol probes, a nephelometer and Particle Soot Absorption Photometer (PSAP), aerosol filters and various radiation instruments. The Mystere was equipped with radiation equipment, a lidar and a POLDER simulator. The results that will be presented here show that the aerosol is not as strongly absorbing as assumed in all modelling estimates of the radiative impact of mineral dust. The visible optical depth of the dust storm exceeds 1.5, and the associated perturbation to the broadband solar upwelling irradiance is an increase of up to 130Wm-2. A clearly detected terrestrial signal is also measured in the 8-12micron atmospheric window with the ARIES interferometer. This atmospheric window is used in the remote sensing of sea surface temperatures (SSTs) by AVHRR and the prescence of the dust leads to errors in the derived AVHRR SSTs of up to approximately -3.5C. Additional results modelling both the solar and terrestrial radiative effects of the Saharan dust outbreak will be reported, and comparisons with the optical properties and optical depths derived from MODIS and the lidar will be presented.

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