Research article
14 Oct 2016
Research article | 14 Oct 2016
Validating MODIS above-cloud aerosol optical depth retrieved from “color ratio” algorithm using direct
measurements made by NASA's airborne AATS and 4STAR sensors
Hiren Jethva1,2, Omar Torres2, Lorraine Remer3, Jens Redemann4, John Livingston5, Stephen Dunagan4, Yohei Shinozuka6, Meloe Kacenelenbogen6, Michal Segal Rosenheimer6, and Rob Spurr7
Hiren Jethva et al.
Hiren Jethva1,2, Omar Torres2, Lorraine Remer3, Jens Redemann4, John Livingston5, Stephen Dunagan4, Yohei Shinozuka6, Meloe Kacenelenbogen6, Michal Segal Rosenheimer6, and Rob Spurr7
- 1Universities Space Research Association, Goddard Earth Sciences Technology and Research (GESTAR), Columbia, MD 21044, USA
- 2Earth Science Division, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center,
Greenbelt, MD 20771, USA
- 3Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
- 4Earth Science Division, NASA Ames Research Center, Moffett Field, CA 94035, USA
- 5SRI International, Menlo Park, CA 94025, USA
- 6Bay Area Environmental Research Institute, NASA Ames Research Center, Moffett Field, CA 94035, USA
- 7RT Solutions, Cambridge, MA 02138, USA
- 1Universities Space Research Association, Goddard Earth Sciences Technology and Research (GESTAR), Columbia, MD 21044, USA
- 2Earth Science Division, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center,
Greenbelt, MD 20771, USA
- 3Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
- 4Earth Science Division, NASA Ames Research Center, Moffett Field, CA 94035, USA
- 5SRI International, Menlo Park, CA 94025, USA
- 6Bay Area Environmental Research Institute, NASA Ames Research Center, Moffett Field, CA 94035, USA
- 7RT Solutions, Cambridge, MA 02138, USA
Correspondence: Hiren Jethva (hiren.t.jethva@nasa.gov)
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Received: 23 May 2016 – Discussion started: 22 Jun 2016 – Revised: 19 Sep 2016 – Accepted: 21 Sep 2016 – Published: 14 Oct 2016
Abstract. We present the validation analysis of above-cloud aerosol optical depth (ACAOD) retrieved from the “color ratio” method applied to MODIS cloudy-sky reflectance measurements using the limited direct measurements made by NASA's airborne Ames Airborne Tracking Sunphotometer (AATS) and Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) sensors. A thorough search of the airborne database collection revealed a total of five significant events in which an airborne sun photometer, coincident with the MODIS overpass, observed partially absorbing aerosols emitted from agricultural biomass burning, dust, and wildfires over a low-level cloud deck during SAFARI-2000, ACE-ASIA 2001, and SEAC4RS 2013 campaigns, respectively. The co-located satellite-airborne matchups revealed a good agreement (root-mean-square difference < 0.1), with most matchups falling within the estimated uncertainties associated the MODIS retrievals (about −10 to +50 %). The co-retrieved cloud optical depth was comparable to that of the MODIS operational cloud product for ACE-ASIA and SEAC4RS, however, higher by 30–50 % for the SAFARI-2000 case study. The reason for this discrepancy could be attributed to the distinct aerosol optical properties encountered during respective campaigns. A brief discussion on the sources of uncertainty in the satellite-based ACAOD retrieval and co-location procedure is presented. Field experiments dedicated to making direct measurements of aerosols above cloud are needed for the extensive validation of satellite-based retrievals.
