Implementing a Chemistry Package for Representing Aerosol Indirect Effects in a Global Weather Forecasting Model

Atmospheric aerosols play an important role in cloud formation by acting as cloud condensation nuclei (CCN), and in this presentation we describe their indirect effects on simulated precipitation in a numerical weather prediction testbed. To this end, a simplified chemistry package based on the Goddard Chemistry Aerosol Radiation and Transport scheme of Weather Research and Forecasting with Chemistry was implemented in the Global/Regional Integrated Model System (GRIMs) along with derived CCN effects in both cumulus parameterization and microphysics schemes. GRIMs at approximately 50 km grid spacing was integrated for 10 days in July 2016 with analyses generated from the Korea Meteorological Administration’s United Model forecast system, and the number of forecasts is 15. Overall, the amount of incoming shortwave radiation reaching the ground is reduced by the increase in warm clouds due to suppressed autoconversion, which leads to a reduction in precipitation. The amount of heavier precipitation increases over the Tropics due to the inclusion of enhanced riming effects in the case of deep precipitating convection. Seasonal simulations were also conducted to investigate the aerosol-thermodynamics-dynamics interactions.