27 Apr 2023
 | 27 Apr 2023

Cloud top heights and aerosol layer properties from EarthCARE lidar observations: the A-CTH and A-ALD products

Ulla Wandinger, Moritz Haarig, Holger Baars, David Donovan, and Gerd-Jan van Zadelhoff

Abstract. The Atmospheric Lidar (ATLID) on the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) provides vertically resolved information on aerosols and clouds at the global scale. This paper describes the algorithms for the determination of cloud-top-height and aerosol-layer information from ATLID Level 1b (L1b) and Level 2a (L2a) input data. The ATLID L2a Cloud Top Height (A-CTH) and ATLID Aerosol Layer Descriptor (A-ALD) products are developed to ensure the provision of atmospheric layer products in continuation of the heritage from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Moreover, the products serve as input for synergistic algorithms that make use of data from ATLID and EarthCARE’s Multi Spectral Imager (MSI). Therefore, the products are provided on the EarthCARE Joint Standard Grid (JSG). A wavelet covariance transform (WCT) method with flexible thresholds is applied to determine layer boundaries from the ATLID Mie co-polar signal. Strong features detected with a horizontal resolution of one JSG pixel (approximately 1 km) or 11 JSG pixels are classified as thick or thin clouds, respectively. The top height of the uppermost cloud layer together with information on cloud layering is stored in the A-CTH product for further use in the generation of the ATLID-MSI Cloud Top Height (AM-CTH) synergy product. Aerosol layers are detected as weaker features at a resolution of 11 JSG pixels. Layer-mean optical properties are calculated from the ATLID L2a Extinction, Backscatter and Depolarization (A-EBD) product and stored in the A-ALD product, which also contains the aerosol optical thickness (AOT) of each layer, the stratospheric AOT, and the AOT of the entire atmospheric column. The latter parameter is used to produce the synergistic ATLID-MSI Aerosol Column Descriptor (AM-ACD) later in the processing chain. Several quality criteria are applied in the generation of A-CTH and A-ALD, and respective information is stored in the products. The functionality and performance of the algorithm are demonstrated by applying it to common EarthCARE test scenes. Conclusions are drawn for the application to real-world data and the validation of the products after the launch of EarthCARE.

Ulla Wandinger 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 egusphere-2023-748', Anonymous Referee #1, 17 May 2023
  • RC2: 'Comment on egusphere-2023-748', Anonymous Referee #2, 19 May 2023
  • RC3: 'Comment on egusphere-2023-748', Anonymous Referee #3, 22 May 2023

Ulla Wandinger et al.

Data sets

EarthCARE level-2 demonstration products from simulated scenes Gerd-Jan van Zadelhoff, Howard W. Barker, Edward Baudrez, Sebastian Bley, Nicolas Clerbaux, Jason N. S. Cole, Jos de Kloe, Nicole Docter, Carlos Domenech, David P. Donovan, Jean-Louis Dufresne, Michael Eisinger, Juergen Fischer, Raquel García-Marañón, Moritz Haarig, Robin J. Hogan, Anja Hünerbein, Pavlos Kollias, Rob Koopman, Nils Madenach, Shannon L. Mason, Rene Preusker, Bernat Puigdomènech Treserras, Zhipeng Qu, Manuel Ruiz-Saldaña, Mark Shephard, Almudena Velázquez-Blazquez, Nadja Villefranque, Ulla Wandinger, Ping Wang, and Tobias Wehr

Ulla Wandinger et al.


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Short summary
We introduce the algorithms that have been developed to derive cloud-top-height and aerosol-layer products from observations with the Atmospheric Lidar (ATLID) onboard the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE). The products provide information on the uppermost cloud and geometrical and optical properties of aerosol layers in an atmospheric column. They can be used individually, but also serve as input for algorithms that combine observations with EarthCARE’s lidar and imager.