HETEAC – the Hybrid End-To-End Aerosol Classification model for EarthCARE

Abstract

Abstract. The Hybrid End-To-End Aerosol Classification (HETEAC) model for the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission is introduced. The model serves as the common baseline for the development, evaluation, and implementation of EarthCARE algorithms. It guarantees the consistency of different aerosol products from the multi-instrument platform and facilitates the conformity of broad-band optical properties needed for EarthCARE radiative-closure assessments. While the hybrid approach ensures that the theoretical description of aerosol microphysical properties is consistent with the optical properties of the measured aerosol types, the end-to-end model permits the uniform representation of aerosol types in terms of microphysical, optical, and radiative properties. Four basic aerosol components with prescribed microphysical properties are used to compose various natural and anthropogenic aerosols of the troposphere. The components contain weakly and strongly absorbing fine-mode and spherical and non-spherical coarse-mode particles and thus are representative for pollution, smoke, sea salt, and dust, respectively. Their microphysical properties are selected such that good coverage of the observational phase space of intensive, i.e., concentration-independent, optical aerosol properties derived from EarthCARE measurements is obtained. Mixing rules to calculate optical and radiative properties of any aerosol blend composed of the four basic components are provided. Applications of HETEAC in the generation of test scenes, the development of retrieval algorithms for stand-alone and synergistic aerosol products from EarthCARE's atmospheric lidar (ATLID) and multi-spectral imager (MSI), and for radiative-closure assessments are introduced. Finally, the implications of simplifying model assumptions and possible improvements are discussed, and conclusions for future validation and development work are drawn.

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

“…10d. This plot nicely demonstrates the ability of ATLID to provide layermean values of the particle extinction and backscatter coefficients, lidar ratio, and linear depolarization ratio, which are the input for aerosol typing based on L2 products (Wandinger et al, 2023). Figure 10e shows the columnar aerosol classification probabilities following from this typing approach (see Sect.…”

“…Height-resolved aerosol classification probabilities are calculated with the A-PRO processor and stored in the A-TC product for mixtures of seven aerosol types (dust, marine aerosol, continental pollution, smoke, dusty smoke, dusty aerosol mix, ice; Donovan et al, 2023a). The aerosol classification follows from the Hybrid End-to-End Aerosol Classification (HETEAC) model developed for EarthCARE (Wandinger et al, 2023). The ice is considered to indicate the presence of optically thin ice-containing layers (e.g., diamond dust, subvisible cirrus) that have not been identified as clouds and thus occur in the aerosol products.…”

“…EarthCARE mission requirements call for the quantification of absorbing or non-absorbing aerosols from natural and anthropogenic sources. Information on the spectral AOT is of interest in this context (see, e.g., Wandinger et al, 2023) and can be gained by combining ATLID measurements at 355 nm with MSI observations at 670 nm (over land and ocean) and 865 nm (over ocean) available from the MSI AOT product (M-AOT; Docter et al, 2023). Respective Ångström exponents, together with track-to-swath extrapolations, are provided in the AM-ACD product (Haarig et al, 2023).…”

Assessing Lidar Ratio Impact on CALIPSO Retrievals Utilized for the Estimation of Aerosol SW Radiative Effects across North Africa, the Middle East, and Europe

“…The advent of the EarthCARE satellite (expected launch on May 2024), a joint mission of the European Space Agency (ESA), and the Japan Aerospace Exploration Agency (JAXA) will substantially upgrade the monitoring capacity from space [177]. Moreover, synergies with CALIPSO will facilitate a more robust aerosol typing via the harmonization of aerosol optical properties at 355 nm (EarthCARE) and 532 nm (CALIPSO) [178]. The HETEAC (Hybrid End-To-End Aerosol Classification) retrieval algorithm (developed for the Earth-CARE (Cloud, Aerosol, and Radiation Explorer) satellite mission) classifies tropospheric aerosol species in two fine modes (weakly/strongly absorbing) and in two coarse modes (spherical, non-spherical), resembling typical conditions met in the real world [178].…”

“…Moreover, synergies with CALIPSO will facilitate a more robust aerosol typing via the harmonization of aerosol optical properties at 355 nm (EarthCARE) and 532 nm (CALIPSO) [178]. The HETEAC (Hybrid End-To-End Aerosol Classification) retrieval algorithm (developed for the Earth-CARE (Cloud, Aerosol, and Radiation Explorer) satellite mission) classifies tropospheric aerosol species in two fine modes (weakly/strongly absorbing) and in two coarse modes (spherical, non-spherical), resembling typical conditions met in the real world [178]. For the first time, joint aerosol, radiation, and cloud observations will be acquired by four instruments (ATLID (atmospheric LIDAR), MSI (Multispectral Instrument), CPR (Cloud Profiling Radar), BBR (Broadband Radiometer)) mounted on the EarthCARE platform [179].…”