The influence of dust optical properties on the colour of simulated MSG-SEVIRI Desert Dust imagery

Abstract

Abstract.Satellite imagery of atmospheric mineral dust is sensitive to the optical properties of the dust, governed by the mineral refractive indices, particle size, and particle shape. In infrared channels the imagery is also sensitive to the dust layer height and to the surface and atmospheric environment. Simulations of mineral dust in infrared 'Desert Dust' imagery from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) have been performed, using the COSMO-MUSCAT (COSMO: are calculated for a number of different dust refractive index databases, along with several values of the particle aspect ratio, denoting the particle shape. It is found that spherical particles do not appear to be sufficient to describe fully the resultant colour of the dust in the infrared imagery. Comparisons of SEVIRI and simulation colours indicate that of the dust types tested, the dust refractive index dataset produced by Volz (1973) shows the most similarity in the colour response to dust in the SEVIRI imagery, although the simulations have a smaller range of colour than do the observations. It is also found that the thermal 15 imagery is most sensitive to intermediately sized particles (radii between 0.9 and 2.6 µm): larger particles are present in too small a concentration in the simulations, as well as with insufficient contrast in extinction between wavelength channels, to have much ability to perturb the resultant colour in the SEVIRI dust imagery.

Transport of Mineral Dust and Its Impact on Climate

“…Satellite data sets are widely used for model validation, however, different measures provided by the satellite instrument and the model simulations can be challenging. To account for this, numerical tool boxes are developed in order to overcome these differences: Radiative transfer models such as RTTOV (Radiative Transfer for TOVs) are adapted to the needs of models simulating the atmospheric dust cycle allowing for an improved understanding of satellite-based dust products [40] and thus for a more accurate comparison against model simulations.…”