Scientific Colloquium
May 25, 2016, 3:30 p.m., Building 3 Auditorium

"Quantifying Aerosol Influences on the Cloud Radiative Effect"  

Although evidence of aerosol influences on the microphysical properties of shallow liquid cloud fields abounds, a rigorous assessment of aerosol effects on the radiative properties of these clouds has proved to be elusive because of adjustments in the evolving cloud system.  We will demonstrate through large numbers of idealized large eddy simulation and 14 years of surface-based remote sensing at a continental US site that the existence of a detectable cloud microphysical response to aerosol perturbations is neither a necessary, nor a sufficient condition for detectability of a radiative response.  We will use a new framework that focuses on the cloud field properties that most influence shortwave radiation, e.g., cloud fraction, albedo, and liquid water path.  In this framework, scene albedo is shown to be a robust function of cloud fraction for a variety of cloud systems, and appears to be insensitive to averaging scale.  The albedo-cloud fraction framework will be used to quantify the cloud radiative effect of shallow liquid clouds and to demonstrate (i) the primacy of cloud field properties such as cloud fraction and liquid water path for driving the cloud radiative effect; and (ii) that the co-variability between meteorological and aerosol drivers has a strong influence on the detectability of the cloud radiative effect, regardless of whether a microphysical response is detected.  A broad methodology for systematically quantifying the cloud radiative effect will be presented.
About the Speaker:

Graham Feingold is a research scientist at NOAA's Earth System Research Laboratory in Boulder, Colorado. His interests lie in aerosol-cloud-precipitation interactions and implications for climate change. His focus is on process level studies using high resolution models and observations (aircraft and surface remote sensing) at the cloud scale (10s of meters to 10s of kms). He received his PhD in Geophysics and Planetary Sciences (summa cum laude) from the Tel Aviv University in 1989. His research interests include lidar and radar remote sensing of clouds and aerosol, modeling and remote sensing of aerosol-cloud interactions ("indirect effects"), "cloud burning" or the "semi-direct effect," and cloud processing of aerosol through multiphase chemistry. He has authored or co-authored more than 150 peer-reviewed articles on these subjects. Feingold was a lead author on the IPCC AR5 Chapter 7 (Clouds and Aerosols), and is an associate editor of the online journal Atmospheric Chemistry and Physics (ACP), a contributor to the Climate Change Science Program, and a chapter author of the International Aerosol-Precipitation Scientific Assessment Project. He has served as a NOAA representative to EarthCare and IGAC and is currently on the Aerosol-Cloud-Precipitation-Climate (ACPC) steering committee.

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