Abstract
Abstract. In August 2018, the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) project released a new level 3 stratospheric aerosol profile data product derived from nearly 12 years of measurements acquired by the spaceborne Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP). This monthly averaged, gridded level 3 product is based on version 4 of the CALIOP level 1B and level 2 data products, which feature significantly improved calibration that now makes it possible to reliably retrieve profiles of stratospheric aerosol extinction and backscatter coefficients at 532 nm. This paper describes the science algorithm and data handling techniques that were developed to generate the CALIPSO version 1.00 level 3 stratospheric aerosol profile product. Further, we show that the extinction profiles (retrieved using a constant lidar ratio of 50 sr) capture the major stratospheric perturbations in both hemispheres over the last decade resulting from volcanic eruptions, extreme smoke events, and signatures of stratospheric dynamics. Initial assessment of the product by intercomparison with the stratospheric aerosol retrievals from the Stratospheric Aerosol and Gas Experiment III (SAGE III) on the International Space Station (ISS) indicates good agreement in the tropical stratospheric aerosol layer (30∘ N–30∘ S), where the average difference between zonal mean extinction profiles is typically less than 25 % between 20 and 30 km (CALIPSO biased high). However, differences can exceed 100 % in the very low aerosol loading regimes found above 25 km at higher latitudes. Similarly, there are large differences (≥100 %) within 2 to 3 km above the tropopause that might be due to cloud contamination issues.
Highlights
While the bulk of the global distribution of atmospheric aerosols is concentrated within the planetary boundary layer and free troposphere, the persistent aerosol burden in the stratosphere has long been known to have important implications for Earth’s climate (Turco et al, 1980)
The previous section demonstrated that the retrieved aerosol extinction coefficients reported by the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) level 3 stratospheric aerosol product agree well with those reported by Stratospheric Aerosol and Gas Experiment (SAGE) III between 20 and 30 km within tropical latitudes (30◦ S–30◦ N), though the disparities between the two sets of www.atmos-meas-tech.net/12/6173/2019/
In this paper we have provided a detailed account of the algorithm used to construct the recently released CALIPSO level 3 stratospheric aerosol profile product version 1.00
Summary
While the bulk of the global distribution of atmospheric aerosols is concentrated within the planetary boundary layer and free troposphere, the persistent aerosol burden in the stratosphere has long been known to have important implications for Earth’s climate (Turco et al, 1980). One of the issues impacting the retrieval of stratospheric aerosol extinction was the realization that the standard calibration altitude of CALIOP, which was originally fixed at 30–34 km (Powell et al, 2009), was not completely free of aerosols, and applying the molecular normalization technique at these altitudes would bias the aerosol extinction profiles (Vernier et al, 2009). This issue has since been addressed with the release of the version 4 (V4) family of CALIPSO data products in November 2016. A discussion and concluding remarks are given in Sects. 4 and 5, respectively
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