Modeling aerosols and their interactions with shallow cumuli during the 2007 CHAPS field study
Article first published online: 7 FEB 2013
©2013. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Atmospheres
Volume 118, Issue 3, pages 1343–1360, 16 February 2013
How to Cite
2013), Modeling aerosols and their interactions with shallow cumuli during the 2007 CHAPS field study, J. Geophys. Res. Atmos., 118, 1343–1360, doi:10.1029/2012JD018218., , , , , , , , and (
- Issue published online: 1 APR 2013
- Article first published online: 7 FEB 2013
- Accepted manuscript online: 23 JAN 2013 07:00PM EST
- Manuscript Accepted: 26 NOV 2012
- Manuscript Revised: 16 NOV 2012
- Manuscript Received: 4 JUN 2012
- shallow cumuli;
 The Weather Research and Forecasting model coupled with chemistry, using 2 km horizontal grid spacing, is used to simulate two important relationships between aerosols and clouds in the vicinity of Oklahoma City during the June 2007 Cumulus Humilis Aerosol Processing Study (CHAPS). First, the model reproduces the trends of higher nitrate volume fractions in cloud droplet residuals compared to interstitial nonactivated aerosols, as measured using an aerosol mass spectrometer. Comparing simulations with cloud chemistry turned on and off, we show that nitric acid vapor uptake by cloud droplets explains the higher nitrate content of cloud droplet residuals. Second, the model reasonably represents the observations of the first aerosol indirect effect where pollutants in the vicinity of Oklahoma City increase cloud droplet number concentrations and decrease the droplet effective radius. In addition, as documented using an offline optical code, simulated aerosol optical properties depend on several compensating effects including aerosol water content, size-resolved chemical composition, and refractory index of various particle chemical species. All of our four sensitivity test cases clearly show an increase in simulated absorption and a decrease in single scattering albedo within the Oklahoma City plume relative to conditions outside the plume. While previous studies have often focused on cloud–aerosol interactions in stratiform and deep convective clouds, this study highlights the ability of regional-scale models to represent some of the important aspects of cloud–aerosol interactions associated with fields of short-lived shallow cumuli.