Parameterization of the cloud-mediated radiative forcing of climate due to aerosols in the two-way coupled WRF-CMAQ over the continental United States
Abstract
Atmospheric emissions resulting from consumption of fossil fuels by human activities contribute to global warming and degrade air quality. The IPCC (2007) concludes that the total direct aerosol radiative forcing is estimated to be -0.5 [±0.4] W m-2, with a medium-low level of scientific understanding, while the radiative forcing due to the cloud albedo effect (also referred to as first indirect), is estimated to be -0.7 [-1.1, +0.4] W m-2, with a low level of scientific understanding. For a given cloud liquid water content, an increase in the cloud droplet number concentration implies a decrease in the effective radius, thus increasing the cloud reflectivity; this is know as the first indirect aerosol effect. The second indirect aerosol effect is based on the idea that decreasing the mean droplet size in the presence of enhanced aerosols decreases the cloud precipitation efficiency, producing clouds with a larger liquid water content and longer lifetime. In this study, the indirect aerosol effect is estimated with the newly developed two-way coupled WRF-CMAQ over the continental United States. The cloud droplet number concentrations are diagnosed from the activation of CMAQ-predicted aerosol. The resulting cloud droplet number is used to calculate variations in droplet effective radius, which in turn allows us to estimate aerosol effects on cloud optical depth and microphysical processes using a two-moment treatment of cloud water (cloud water mass and cloud droplet number) to model effects on precipitation. With the satellite observation data such as CERES, MODIS and CALIPSO, we will evaluate the cloud properties such as cloud optical depth, cloud droplet effective radius, and liquid water content and indirect aerosol forcing in the newly-developed coupled WRF-CMAQ.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A23A0205Y
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles;
- 0319 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud optics;
- 0321 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud/radiation interaction;
- 0320 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud physics and chemistry