MFRSR-retrieved Intensive Aerosol Properties Under Partly Cloudy Days: Uncertainties and Corrections

Evgueni Kassianov Pacific Northwest National Laboratory
Jaime Barnard University of Nevada Reno
Connor Flynn Pacific Northwest National Laboratory
Chuck Long NOAA Global Monitoring Division/CIRES
Larry Berg Pacific Northwest National Laboratory

Category: Aerosol Properties

Working Group: Aerosol Life Cycle

Image Thumbnail
Cloud-induced bias of DDR as function of cloud optical depth (COD) and fractional sky cover (FSC).

Several studies have demonstrated that the aerosol single-scattering albedo and asymmetry parameter carry the largest uncertainty of any parameters associated with direct aerosol forcing (e.g., McComiskey et al. 2008). Under clear-sky conditions, these intensive aerosol properties can be provided quite accurately by Multifilter Rotating Shadowband Radiometers (MFRSRs) (e.g., Kassianov et al. 2007). The MFRSR-based aerosol retrieval, which is applied to accomplish this task, relies on the ratio of the diffuse and direct surface irradiances, so-called the diffuse-to-direct ratio (DDR). Broken clouds are observed frequently over the ARM SGP site, and they can substantially modulate the diffuse irradiance, and consequently the DDR. Thus, the cloud-induced changes to the DDR may significantly contaminate the MFRSR-derived intensive aerosol properties. Here we apply model simulations (attached figure) to quantify the cloud contamination and suggest corrections for reducing the contamination impact on the retrievals. The model results are accompanied by analyses of cloudy-sky data collected during the CHAPS/CLASIC campaigns. McComiskey, A, SE Schwartz, B Schmid, H Guan, ER Lewis, P Ricchiazzi, and JA Ogren. 2008. “Direct aerosol forcing: Calculation from observables and sensitivities to inputs.” Journal of Geophysical Research 113, D09202, doi:10.1029/2007JD009170. Kassianov, EI, Flynn, CJ, Ackerman, TP, and Barnard, JC. 2007. “Aerosol single-scattering albedo and asymmetry parameter from MFRSR observations during the ARM Aerosol IOP 2003.” Atmospheric Chemistry and Physics 7: 3341–3351.

This poster will be displayed at ASR Science Team Meeting.