Evaluation of nucleation algorithms and their impacts on simulated aerosol number and size distributions and cloud properties

Atmospheric aerosols affect regional/global air quality and meteorology as well as long-term climate through climate-chemistry-aerosol-cloud-radiation interactions. The impacts of aerosol feedbacks, from direct effects on radiation to indirect effects by acting as cloud condensation nuclei and modifying cloud properties, strongly depend on the number and mass concentrations as well as size distribution of aerosols. The formation of new particles, widely observed at various locations and conditions, is one of the most important processes affecting aerosol number concentrations and size distributions. A number of theories and empirical methods have been proposed to simulate new particle formation, each with its own merits and limitations. Furthermore, large uncertainties exist in the simulated formation rates of new particles. In this study, one homogeneous nucleation parameterization (i.e., empirical power-law based on cluster activation theory) and one ion-mediated nucleation parameterization will be implemented into the Global-through-Urban Weather Research and Forecasting model with Chemistry (GU-WRF/Chem) to evaluate their performance on a global scale. The impacts of different nucleation algorithms on simulated aerosol number concentrations, aerosol size distribution, and cloud properties will be examined. The simulations for August 2002 will be evaluated against field measurement data from the 2002 Aerosol Nucleation and Real Time Characterization Experiment (ANARChE) in Atlanta, Georgia, as well as additional observations over rural/remote/coastal/marine areas from literatures.