Mineralogy sensitive ice nucleation parameterizations in Dust Regional Atmospheric Model (DREAM)

The Sahara Desert is the major source of mineral dust, which is a significant portion of atmospheric aerosol. Mineral dust particles play a role in radiative balance, with a direct effect and by influencing cloud formation and lifetime. They have been recognized as highly efficient ice nuclei, fostering the development of parameterizations for immersion and deposition freezing involving dust particles. Feldspar minerals have shown to be a significantly more efficient ice nucleating agents than other dust minerals which led to the development of a ‘mineralogy sensitive’ immersion freezing parameterization. The investigation of the relative efficiency of quartz compared to feldspars for the immersion ice nucleation, based upon literature data and new experiments, led to the development of a new parameterization to be applied to mineral dust concentrations. Within numerical models, explicit simulation of mineral dust fractions enables the use of ‘mineralogy sensitive’ immersion parameterizations.

The operational DREAM model calculates the number of ice nuclei,but does not take into consideration the mineral composition of dust. In this study, instead, we use DREAM model to simulate the atmospheric cycle of feldspar and quartz fractions of dust. Dust mineral composition is used to calculate ice nucleating particle concentrations based on mineral-specific immersion freezing parameterizations. A case study related to the observations of geometrical and microphysical characteristics of the clouds formed in the Mediterranean, in April 2016 is considered. We compare the model results with ice nucleating particle concentrations retrieved using lidar and radar ground-based remote sensing observations at Cyprus and Potenza. The analysis explores how the mineral composition of dust and the parameterization of its effects on ice initiation could further improve ice nucleation representation in numerical models.