Atmospheric ice nucleating particle measurements and parameterization representative for Indian region.

Atmospheric ice nucleating particle (INP) concentration measurements over the Indian region are very sparse; hence more observations are required to represent heterogeneous ice nucleation processes in the regional cloud models for better accuracy. In this work, the INP ability and size of ambient aerosol particles at a tropical high altitude station were studied. Ice nucleation experiments were conducted at temperatures between −25 and −34 °C and water supersaturation conditions up to 102%. The mean INP concentrations varied from 1.1 to 9.5 L−1 and correlated well with coarse mode aerosol particle concentration (> 1 μm). Higher INP concentrations were observed when the aerosol loading was influenced by the regions such as Mumbai metro city, Gujarat, Thar desert region, and the Arabian sea region close to the Oman coast. An empirical equation was formulated to represent the INP concentrations using supercooled temperature and coarse mode aerosol particle concentration. The sensitivity of new heterogeneous ice nucleation parameterization was tested against literature INP parameterizations using Weather Research and Forecasting (WRF) model. The model results show that the new parameterization helped to simulate the rainfall amount better as compared to the old formulations. Better reproduction of convection and possible reduction of biases in the formation of cloud ice in the cloud-resolving model improved the model accuracy. These results show the importance of implementing new INP parameterization in a real-time forecast model to improve the regional climate model forecasting. • Measured INP concentration online using a Continuous Flow Diffusion Chamber. • Heterogeneous ice nucleation experiments were conducted at mixed-phase cloud conditions. • An empirical equation was formulated to represent INP using supercooled temperature and coarse mode aerosol concentration. • The model results using new parameterization helped to simulate the rainfall amount better as compared to old formulations. [ABSTRACT FROM AUTHOR]