On the composition of non-volatile material in upper tropospheric aerosols and cirrus crystals

As part of an airborne cirrus experiment over the Alps, samples of non-volatile material in upper tropospheric aerosols and cirrus crystals were taken at 9.4 km altitude in January 1992. At that time high backscattering coefficients were measured by Lidars over Europe in this altitude region. Aircraft samples showed that minerals were dominant in micrometer sized interstitial and out-of-cloud particles and in cirrus crystal residues. The results were compared to similar chemical signatures from source samples prepared from Pinatubo ash and Saharan dust. The chemical signatures of interstitial and out-of-cloud particles were similar to those of the source samples, with a depletion of heavier elements. The crystal residues were depleted in lighter elements (Na-S) and enriched in the heavier elements Ti-Cd.