Unveiling aerosol–cloud interactions – Part 1: Cloud contamination in satellite products enhances the aerosol indirect forcing estimate

Christensen, M; Neubauer, D; Poulsen, C; Thomas, G; McGarragh, G; Povey, A; Proud, S; Grainger, R

Journal article

Unveiling aerosol–cloud interactions – Part 1: Cloud contamination in satellite products enhances the aerosol indirect forcing estimate

Abstract:: Increased concentrations of aerosol can enhance the albedo of warm low-level cloud. Accurately quantifying this relationship from space is challenging due in part to contamination of aerosol statistics near clouds. Aerosol retrievals near clouds can be influenced by stray cloud particles in areas assumed to be cloud-free, particle swelling by humidification, shadows and enhanced scattering into the aerosol field from (3-D radiative transfer) clouds. To screen for this contamination we have developed a new cloud–aerosol pairing algorithm (CAPA) to link cloud observations to the nearest aerosol retrieval within the satellite image. The distance between each aerosol retrieval and nearest cloud is also computed in CAPA.
Results from two independent satellite imagers, the Advanced Along-Track Scanning Radiometer (AATSR) and Moderate Resolution Imaging Spectroradiometer (MODIS), show a marked reduction in the strength of the intrinsic aerosol indirect radiative forcing when selecting aerosol pairs that are located farther away from the clouds (−0.28±0.26 W m−2) compared to those including pairs that are within 15 km of the nearest cloud (−0.49±0.18 W m−2). The larger aerosol optical depths in closer proximity to cloud artificially enhance the relationship between aerosol-loading, cloud albedo, and cloud fraction. These results suggest that previous satellite-based radiative forcing estimates represented in key climate reports may be exaggerated due to the inclusion of retrieval artefacts in the aerosol located near clouds.

Publication status:: Published

Peer review status:: Peer reviewed

Actions

Email

Email this record

Send the bibliographic details of this record to your email address.

Your Email
Please enter the email address that the record information will be sent to.

-
Your message (optional)
Please add any additional information to be included within the email.
Cite

Cite this record

APA Style

Christensen, M., Neubauer, D., Poulsen, C., Thomas, G., McGarragh, G., Povey, A., Proud, S., & Grainger, R. (2017). Unveiling aerosol–cloud interactions – Part 1: Cloud contamination in satellite products enhances the aerosol indirect forcing estimate. Atmospheric Chemistry and Physics, 17(21), 13151–13164.

MLA Style

Christensen, M., et al. “Unveiling Aerosol–Cloud Interactions – Part 1: Cloud Contamination in Satellite Products Enhances the Aerosol Indirect Forcing Estimate.” Atmospheric Chemistry and Physics, vol. 17, no. 21, European Geosciences Union, 2017, pp. 13151–64.

Chicago Style

Christensen, M, D Neubauer, C Poulsen, G Thomas, G McGarragh, A Povey, S Proud, and R Grainger. 2017. “Unveiling Aerosol–Cloud Interactions – Part 1: Cloud Contamination in Satellite Products Enhances the Aerosol Indirect Forcing Estimate.” Atmospheric Chemistry and Physics 17 (21): 13151–64.
Share
Print