Preprints
https://doi.org/10.5194/amt-2021-169
https://doi.org/10.5194/amt-2021-169

  22 Jun 2021

22 Jun 2021

Review status: this preprint is currently under review for the journal AMT.

Biomass Burning Aerosol Heating Rates from the ORACLES 2016 and 2017 Experiments

Sabrina P. Cochrane1,2, K. Sebastian Schmidt1,2, Hong Chen1,2, Peter Pilewskie1,2, Scott Kittleman1, Jens Redemann3, Samuel LeBlanc4,5, Kristina Pistone4,5, Michal Segal Rozenhaimer4,5,6, Meloë Kacenelenbogen5, Yohei Shinozuka5,7, Connor Flynn3, Rich Ferrare8, Sharon Burton8, Chris Hostetler8, Marc Mallet9, and Paquita Zuidema10 Sabrina P. Cochrane et al.
  • 1Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, 80303, USA
  • 2University of Colorado, Laboratory for Atmospheric and Space Physics, Boulder, 80303, USA
  • 3School of Meteorology, University of Oklahoma, Norman, Oklahoma, 73019, USA
  • 4Bay Area Environmental Research Institute, Mountain View, 94035, USA
  • 5NASA Ames Research Center, Mountain View, 94035, USA
  • 6Department of Geophysics and Planetary Sciences, Porter School of the Environment and Earth Sciences, Tel-Aviv University, Tel-Aviv, Israel
  • 7Universities Space Research Association/NASA Ames Research Center, Mountain View, 94035, USA
  • 8NASA Langley Research Center, Hampton, VA, 23666, USA
  • 9Centre National de Recherches Météorologiques, UMR3589, Météo-France-CNRS, Toulouse, France
  • 10Department of Atmospheric Sciences, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, 33149, USA

Abstract. Aerosol heating due to shortwave absorption has implications for local atmospheric stability and regional dynamics. The derivation of heating rate profiles from space-based observations is challenging because it requires the vertical profile of relevant properties such as the aerosol extinction coefficient and single scattering albedo (SSA). In the southeast Atlantic, this challenge is amplified by the presence of stratocumulus clouds below the biomass burning plume advected from Africa, since the cloud properties affect the magnitude of the aerosol heating aloft, which may in turn lead to changes in the cloud properties and life cycle. The combination of spaceborne lidar data with passive imagers shows promise for future derivations of heating rate profiles and curtains, but new algorithms require careful testing with data from aircraft experiments where measurements of radiation, aerosol and cloud parameters are better collocated and readily available.

In this study, we derive heating rate profiles and curtains from aircraft measurements during the NASA ObseRvations of CLouds above Aerosols and their intEractionS (ORACLES) project in the southeastern Atlantic. Spectrally resolved irradiance measurements and the derived column absorption allow for the separation of total heating rates into aerosol and gas (primarily water vapor) absorption. The nine cases we analyzed capture some of the co-variability of heating rate profiles and their primary drivers, leading to the development of a new concept: The Heating Rate Efficiency (HRE; the heating rate per unit aerosol extinction). The HRE, which accounts for the overall aerosol loading as well as vertical distribution of the aerosol layer, varies little with altitude as opposed to the standard heating rate. The large case-to-case variability for ORACLES is significantly reduced after converting from heating rate to HRE, allowing us to quantify its dependence on SSA, cloud albedo, and solar zenith angle.

Sabrina P. Cochrane et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-169', Anonymous Referee #1, 21 Jul 2021
  • RC2: 'Comment on amt-2021-169', Anonymous Referee #2, 30 Jul 2021
  • RC3: 'Review of Cochrane et al.', Anonymous Referee #3, 09 Aug 2021

Sabrina P. Cochrane et al.

Sabrina P. Cochrane et al.

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Short summary
This work presents heating rates derived from aircraft observations from the 2016 and 2017 field campaigns of ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS). We separate the total heating rates into aerosol and gas (primarily water vapor) absorption, and explore some of the co-variability of heating rate profiles and their primary drivers, leading to the development of a new concept: The Heating Rate Efficiency (HRE; the heating rate per unit aerosol extinction).