Investigating the role of dust in ice nucleation within clouds and further effects on the regional weather system over East Asia - Part 1: Model development and validation

Abstract

The GOCART-Thompson microphysics scheme coupling the GOCART aerosol model and the aerosol-aware Thompson-Eidhammer microphysics scheme has been implemented in the WRF-Chem to quantify and evaluate the effect of dust on the ice nucleation process in the atmosphere by serving as ice nuclei (IN). The performance of the GOCART-Thompson microphysics scheme in simulating the effect of dust in atmospheric ice nucleation is then evaluated over East Asia during spring, a typical dust-intensive season, in 2012. Based upon the dust emission reasonably reproduced by WRF-Chem, the effect of dust on atmospheric cloud ice water content is well reproduced. With abundant dust particles serving as IN, the simulated ice water mixing ratio and ice crystal number concentration increases by 15 and 7% on average over the dust source region and downwind areas during the investigated period. The comparison with the ice water path from satellite observations demonstrated that the simulation of the cloud ice profile is substantially improved by considering the indirect effect of dust particles in the simulations. Additional sensitivity experiments are carried out to optimize the parameters in the ice nucleation parameterization in the GOCART-Thompson microphysics scheme. Results suggest that lowering the threshold relative humidity with respect to ice to 100% for the ice nucleation parameterization leads to further improvement in cloud ice simulation.