A243-04
A Study of Spectral Absorption Aerosol Optical Depth from the 2016-2018 ORACLES Campaigns
Wednesday, 16 December 2020: 16:12
Virtual
Logan Mitchell1, Connor J. Flynn1, Jens Redemann1, Kristina Pistone2, Samuel E LeBlanc3, Meloe S Kacenelenbogen2 and Sebastian Schmidt4, (1)University of Oklahoma, School of Meteorology, Norman, OK, United States, (2)NASA Ames Research Center, Moffett Field, CA, United States, (3)NASA Ames Research Center, Bay Area Environmental Research Insitute, Moffett Field, CA, United States, (4)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States
Abstract:
Absorption aerosol optical depth (AAOD) relates to the light absorption of an aerosol column and is critical to understanding that column’s radiative effect and its associated atmospheric heating rate. An improved understanding of AAOD will greatly assist in decreasing the uncertainties associated with direct aerosol radiative forcing. However, this remains a challenging quantity to measure with sufficient accuracy for typical aerosol burdens at ambient atmospheric conditions. This project performs a closure study between
in situ measurements of aerosol absorption and ambient AAOD retrieved from passive photometry during the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) 2016-2018 suborbital campaigns. We first define our analytical framework to demonstrate how well the
in situ extinction observations can be reconciled with the airborne column aerosol optical depth (AOD) measurements, as these quantities are more robustly measured and are much better understood than absorption alone. This framework is then applied to focus on the aerosol absorption properties explicitly, including variations due to wavelength, especially within the understudied ultraviolet spectrum.
In addition to the two above comparisons of in situ vs. column properties, we examine the spectral dependence of these properties from the ORACLES campaigns. The in situ extinction and absorption measurements are reported at nominal red, green, and blue wavelengths, providing the coarse spectral dependence of these optical properties, but lack enough spectral information to carry out more specific applications, such as determining the apportionment of black carbon vs. brown carbon. AOD and AAOD are retrieved via hyperspectral sun/sky photometry measurements from NASA Ames’ Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) and the joint NASA Ames and LASP Solar Spectral Flux Radiometer (SSFR), with the potential to provide a more detailed spectral dependence, especially within the ultraviolet spectrum. Through concurrently exploring AAOD, wavelength dependence, and the ultraviolet spectrum, this project works to better constrain aerosol absorption, which will help to reduce uncertainties in aerosol typing and climate assessments.
