The impact of mineral dust on the day-to-day variability of stratiform cloud glaciation occurrence

Abstract. Two different A-Train satellite cloud phase products were analysed together with an aerosol model reanalysis to assess the global day-to-day variability of cloud thermodynamic phase. This variability was analysed for different mixing-ratios of fine and coarse mineral dust during the period 2007–2010 and within a temperature range from +3 °C to −42 °C. Night‑time stratiform clouds were analysed, including stratocumulus, altocumulus, altostratus and cirrus clouds. This analysis showed that the phase of stratiform clouds is highly dependent on temperature and latitude. However, at equal temperature the average occurrence of fully glaciated stratiform clouds was found to increase for higher dust mixing-ratios on a day-to-day basis at mid- and high latitudes. At −15 °C, the increment of ice cloud occurrence between the lowest and highest mixing-ratio was found to be higher for fine dust (+10 % to +18 % occurrence) than for coarse dust (+5 % to +10 %). Surprisingly, the increments were higher in remote regions (e.g. southern high latitudes) where the average dust-mixing ratios are low.