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Preprints
https://doi.org/10.5194/essd-2020-56
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/essd-2020-56
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  25 May 2020

25 May 2020

Review status
A revised version of this preprint was accepted for the journal ESSD and is expected to appear here in due course.

A Global Space-based Stratospheric Aerosol Climatology (Version 2.0): 1979–2018

Mahesh Kovilakam1,2, Larry Thomason2, Nicholas Ernest1, Landon Rieger3, Adam Bourassa3, and Luis Millán4 Mahesh Kovilakam et al.
  • 1SSAI, Hampton, Virginia, USA
  • 2NASA Langley Research Center, Hampton, Virginia, USA
  • 3University of Saskatchewan, Saskatoon, Saskatchewan, Canada
  • 4NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA

Abstract. A robust stratospheric aerosol climate data record enables the depiction of the radiative forcing of this highly variable component of climate. Since stratospheric aerosol also plays a key role in the chemical processes leading to ozone depletion, stratosphere is one of the crucial parameters in understanding climate change in the past and potential changes in the future. As a part of Stratospheric-tropospheric Processes and their Role in Climate (SPARC) Stratospheric Sulfur and its Role in Climate (SSiRC) activity, the Global Space-based Stratospheric Aerosol Climatology (GloSSAC) was created (Thomason et al., 2018) to support the World Climate Research Programme (WCRP)’s Coupled Model Intercomparison Project Phase 6 (CMIP6) (Zanchettin et al., 2016). This data set is a follow-on to one created as a part of Stratosphere-Troposphere Process and their Role in Climate Project (SPARC)’s Assessment of Stratospheric Aerosol Properties (ASAP) activity(SPARC, 2006) and a data created for Chemistry-Climate Model Initiative (CCMI) in 2012 (Eyring and Lamarque, 2012). Herein, we discuss changes to the original release version including those as a part of v1.1 that was released in September 2018 that primarily corrects an error in the conversion of Cryogenic Limb Array Etalon Spectrometer (CLAES) data to Stratospheric Aerosol and Gas Experiment (SAGE) II wavelengths, and the new release, v2.0. Version 2.0 is focused on improving the post-SAGE II era (after 2005) with the goal to mitigate elevated aerosol extinction in the lower stratosphere at mid and high latitudes noted in v1.0 as noted in Thomason et al. (2018). Changes include the use of version 7.0 of Optical Spectrograph and InfraRed Imaging System(OSIRIS), the recently released Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Lidar Level 3 Stratospheric Aerosol profile monthly product, and the new addition of SAGE III/ISS. Although, the version 7.0 OSIRIS data is substantially improved at its native wavelength of 750 nm, conversion to 525 nm using a constant Angstrom exponent often results in disagreements with SAGEII/ SAGE III/ISS overlap measurements. We, therefore use an observed relationship between OSIRIS extinction at 750 nm and SAGEII/SAGE III/ISS extinction at 525 nm to derive Altitude-Latitude based monthly climatology of Angstrom exponent to compute extinction at 525 nm, resulting in a better agreement between OSIRIS and SAGE measurements. We employ a similar approach to convert OSIRIS 750 nm extinction to 1020 nm extinction for the post-SAGEII period. Additionally, we incorporate the recently released standard CALIPSO stratospheric aerosol profile monthly product into GloSSAC with an improved conversion technique of 532 nm backscatter coefficient to extinction using an observed relationship between OSIRIS 525 nm extinction and CALIPSO 532 nm backscatter. We also investigate for any cloud contamination in OSIRIS/standard CALIPSO stratospheric aerosol product, which may have caused apparent enhancement in the aerosol extinction particularly in the lower stratosphere. SAGE III/ISS data is also incorporated in GloSSAC to extend the climatology to the present and to test the approach used to correct OSIRIS/CALIPSO data. The GloSSAC v2.0 netcdf file is accessible at https://doi.org/10.5067/glossac-l3-v2.0 (Thomason, 2020).

Mahesh Kovilakam et al.

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Mahesh Kovilakam et al.

Data sets

Global Space-based Stratospheric Aerosol Climatology Version 2.0 L. W. Thomason https://doi.org/10.5067/glossac-l3-v2.0

Mahesh Kovilakam et al.

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Short summary
A robust stratospheric aerosol climatology is important as many global climate models (GCMs) make use of observed aerosol properties to prescribe aerosols in the stratosphere. Here, we present version 2.0 of the GloSSAC data set in which a new methodology is used for the post-2005 data that improves the quality of data in the lower stratosphere which includes an improved 1020 nm extinction. Additionally, size information from multi-wavelength measurements of SAGEIII/ISS is provided.
A robust stratospheric aerosol climatology is important as many global climate models (GCMs)...
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