Hagen Telg — Cooperative Institute for Research in Environmental Sciences
Allison C. McComiskey — Brookhaven National Laboratory
Graham Feingold — NOAA- Earth System Research Laboratory
Evgueni Kassianov — Pacific Northwest National Laboratory
Connor J. Flynn — University of Oklahoma School of Meteorology
Jerome D Fast — Pacific Northwest National Laboratory
Category
Absorbing aerosol
Description
A framework for integrating aerosol properties from diverse data sources. All measurements are at the surface unless otherwise noted as satellite-based. Consistency among the modes and variances in aerosol optical properties that originate from measurements made of different portions of the atmospheric column are evaluated. Covariance with contributing properties – chemical and physical – are assessed. Closure is used with the different sources of optical properties and measured surface radiation to quantify error and to determine its source. [RS = Remote Sensing, scattering coefficient σs (m-1), absorption coefficient σa (m-1), hygroscopic factor fRH, single scattering albedo ω0, scattering Ångström exponent, ås, absorption Ångström exponent åa, type = aerosol type from optical models, aerosol size distribution dN/dD, radiative flux f (W m-2), aerosol direct radiative forcing F (W m-2), aerosol radiative forcing efficiency εa (W m-2 τa-1)]
Aerosol direct radiative forcing is determined from a set of optical properties -- aerosol optical depth, single scattering albedo, and asymmetry parameter -- which can be obtained from a range of different measurement techniques. Every technique has unique limitations, thus uncertainty and bias in radiative forcing estimates can vary depending on the measurement approach used. Given that a small fraction of these observations are most widely used for climate change studies, a comprehensive assessment of the interrelationship among all measurements would be of benefit. We present a synthesis of ARM aerosol products from ground-based in situ and remote sensing techniques together with AERONET and satellite observations with the goal of testing these products for consistency. Physical (size distribution) and chemical composition data are used to derive aerosol optical properties and the results are compared to observations from the nephelometer and PSAP instruments as well as derived products from the ground-based radiometers. Dependence on humidity related particle growth is included in the analysis. We furthermore present results from a closure study in which the above properties are used to derive surface broadband shortwave radiative fluxes from a model and compared to the analogous measurements. To obtain the latter we reconstruct vertical profiles of aerosol properties by combining ground-based in-situ aerosol measurements with remotely sensed vertical information of atmospheric properties. The primary objective of this work is to provide greater confidence in the characterization of aerosol optical properties in different regimes in order to better constrain observationally-based and modeled aerosol radiative forcing estimates. Understanding how aerosol optical properties and radiative forcing vary, and covary, in different regions of the globe can improve assumptions required for retrievals and products from satellite-based observations. Understanding how these radiative quantities covary with chemical composition can help to relate that information to processes parameterized in models that address the climate impact of aerosols.
