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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Feb 2019

Research article | 15 Feb 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Measurement Techniques (AMT).

Two decades observing smoke above clouds in the south-eastern Atlantic Ocean: Deep Blue algorithm updates and validation with ORACLES field campaign data

Andrew M. Sayer1,2, N. Christina Hsu2, Jaehwa Lee2,3, Woogyung V. Kim2,3, Sharon Burton4, Marta A. Fenn4,5, Richard A. Ferrare4, Meloë Kacenelenbogen6,7, Samuel LeBlanc6,7, Kristina Pistone6,7, Jens Redemann8, Michal Segal-Rozenhaimer6,7, Yohei Shinozuka6,9, and Si-Chee Tsay2 Andrew M. Sayer et al.
  • 1GESTAR, Universities Space Research Association, Columbia, MD, USA
  • 2NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 3University of Maryland, College Park, MD, USA
  • 4NASA Langley Research Center, Hampton, VA, USA
  • 5Science Systems and Applications, Inc, Hampton, VA, USA
  • 6Bay Area Environmental Research Institute, Moffett Field, CA, USA
  • 7NASA Ames Research Center, Moffett Field, CA, USA
  • 8University of Oklahoma, Norman, OK, USA
  • 9Universities Space Research Association, Mountain View, CA, USA

Abstract. This study presents and evaluates an updated algorithm for quantification of absorbing aerosols above clouds (AACs) from passive satellite measurements. The focus is biomass burning in the south-eastern Atlantic Ocean during the 2016 and 2017 ObserRvations of Aerosols above CLouds and their interactionS (ORACLES) field campaign deployments. The algorithm retrieves the above-cloud aerosol optical depth (AOD) and underlying liquid cloud optical depth, and is intended to be applied to measurements from sensors including the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Moderate Resolution Imaging Spectroradiometers (MODIS), and Visible Infrared Imaging Radiometer Suite (VIIRS). Together, these sensors provide around twenty years of observations to date. Airborne NASA Ames Spectrometers for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) and NASA Langley High Spectral Resolution Lidar 2 (HSRL2) data collected during ORACLES provide important validation for spectral AOD for MODIS and VIIRS; as the SeaWiFS mission ended in 2010, it cannot be evaluated directly. These 4STAR and HSRL2 comparisons are complimentary and reveal performance generally in line with theoretical expectations. At present the two MODIS-based data records seem the most reliable, although there are differences between the deployments. Data collected in the region from other sources are also used to evaluate some assumptions made in the AAC retrieval. Spatiotemporal patterns in the data sets are very similar, and the time series themselves are very strongly correlated with each other (correlation coefficients from 0.95–0.99). Offsets between the time series are thought to be linked to differences in absolute calibration between the sensors, which can also explain some of the differences in validation results. The time series are also strongly correlated (correlations 0.78-0.94) with quantities such as ultraviolet aerosol index, total column AOD from standard MODIS aerosol products, and active fire detections. This suggests that these quantities may also act as proxies for the above-cloud aerosol load in this region, when AAC retrievals are unavailable.

Andrew M. Sayer et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Andrew M. Sayer et al.
Andrew M. Sayer et al.
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Publications Copernicus
Short summary
Aerosols are small particles in the atmosphere such as dust or smoke. They are routinely monitored by satellites due to their importance for climate and air quality. However aerosols above clouds are more difficult to monitor. This study describes an improvement to a technique to monitor light-absorbing aerosols above clouds from four Earth-orbiting satellite instruments. The improved method is evaluated using data from the ORACLES field campaign, which measured these aerosols from aircraft.
Aerosols are small particles in the atmosphere such as dust or smoke. They are routinely...