Evaluating Model Predictions of New Particle Formation in East Asia
Aerosol particles play an important role in Earth’s climate through direct effects on Earth’s radiation budget by absorbing and scattering solar radiation and through indirect effects by affecting cloud formation and cloud properties. Atmospheric aerosol particles can be produced by two different methods. Primary particles (e.g., dust, pollen, sea salt, and soot) are emitted directly to the atmosphere, while secondary particles are formed through nucleation and new particle formation (NPF). To accurately predict aerosol concentrations and their effects on climate, numerical climate models need to accurately simulate nucleation and NPF processes in different regions. A team of scientists, including a Department of Energy researcher at Pacific Northwest National Laboratory, applied a method for predicting NPF treatment in the Weather Research Forecasting-Chem (WRF-Chem) model and evaluated the condensation nuclei (CN) concentrations and frequency of NPF events over East Asia predicted by the model simulations. They found the WRF-Chem model can calculate the growth and sink of nucleated clusters explicitly with 20 aerosol sizes from 1 nm to 10 μm. The model reproduced the observed spatial and temporal variations of CN and cloud condensation nuclei (CCN) number concentrations, the frequency of NPF events, and the contribution of primary and secondary particles within the boundary layer over East Asia and its outflow region. Secondary particles formed have a large impact on CN and CCN concentrations, suggesting that NPF events could influence cloud droplets and aerosol indirect effects. This study is the first to apply and evaluate a three-dimensional model that can explicitly calculate new particle formation in East Asia.
Matsui, H., M. Koike, N. Takegawa, Y. Kondo, A. Takami, T. Takamura, S. Yoon, S.-W. Kim, H.-C. Lim, and J. D. Fast. 2013. “Spatial and Temporal Variations of New Particle Formation in East Asia Using an NPF-Explicit WRF-Chem Model: North-South Contrast in New Particle Formation Frequency,” Journal of Geophysical Research Atmospheres 118,11,647-11,663. DOI: 10.1002/jgrd.50821.