Day 4

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Paper title An enhanced aerosol typing scheme applicable to ground- and space-borne lidars based on - the EarthCARE classification scheme HETEAC
  1. Athina Avgousta Floutsi Leibniz Institute for Tropospheric Research (TROPOS) Speaker
  2. Holger Baars Leibniz Institute for Tropospheric Research (TROPOS)
  3. Moritz Haarig Leibniz Institute for Tropospheric Research (TROPOS)
  4. Ulla Wandinger TROPOS
Form of presentation Poster
  • A1. Atmosphere
    • A1.09 EarthCARE: Preparing for the Scientific Mission Exploitation to Quantify the Impact of Clouds and Aerosols on Radiation
Abstract text The Hybrid End-To-End Aerosol Classification model (HETEAC) [1] has been developed for the upcoming EarthCARE mission [2]. This aerosol classification model is based on a combined experimental and theoretical (hybrid) approach and allows the simulation of aerosol properties, from microphysical to optical and radiative parameters of predefined aerosol types (end-to-end). In order to validate HETEAC, an aerosol typing scheme applicable to both ground-based and spaceborne lidar systems has been developed.
This novel aerosol typing scheme, based on HETEAC, applies the optimal estimation method (OEM) to a combination of lidar-derived intensive aerosol properties (i.e., concentration-independent), to determine the statistically most-likely contribution of aerosol component to the observed aerosol mixture, weighted against a priori knowledge of the system. The aerosol components considered to contribute to an aerosol mixture are four, namely fine, spherical, absorbing (FSA); fine, spherical, non-absorbing (FSNA); coarse, spherical (CS); and coarse, non-spherical (CNS). These four components have been selected from lidar-based experimental data set at 355, 532 and 1064 nm. Their optical and microphysical properties serve as a priori for the retrieval scheme and are in accordance with the ones used in the original HETEAC model, in order to ensure meaningful comparisons. In contrast to HETEAC, which is limited to observations at 355 nm only, the novel typing scheme is flexible in terms of input parameters and can be extended to other wavelengths to exploit the full potential of ground-based multiwavelength-Raman-polarization lidars and thus reduce the ambiguity in aerosol typing. It is thus an algorithm, able to be applied to EarthCARE but also to other lidar systems providing other or more optical products.
The initial guess of the aerosol components contribution that is needed to kick-of the retrieval scheme is the outcome of a decision tree. Using this initial guess, the lidar ratio (355 and 532 nm), particle linear depolarization ratio (355 and 532 nm), extinction-related Ångström exponent and backscatter-related color ratio (at the 532/1064 nm wavelength pair) are calculated (forward model). The final product is the contribution of the four aforementioned aerosol components to an aerosol mixture in terms of relative volume. Once this product meets certain quality assurance flags, it can be used to provide additional products: (a) aerosol component separated backscatter and extinction profiles, (b) aerosol optical depth per aerosol component, (c) volume concentration per component, (d) number concentration per component, (e) effective radius of the observed mixture and (f) refractive index of the mixture.
In this presentation, the aerosol typing scheme will be discussed in detail and it will be applied to several case studies. The application of the algorithm to different atmospheric load scenarios will demonstrate the algorithm’s strengths and limitations. In addition, first results between the HETEAC and OEM comparison will be presented.

[1] Wandinger, Ulla, et al., 2016: "HETEAC: The Aerosol Classification Model for EarthCARE." EPJ Web of Conferences. Vol. 119. EDP Sciences.
[2] llingworth, A., et al., 2014: THE EARTHCARE SATELLITE: The next step forward in global measurements of clouds, aerosols, precipitation and radiation. Bull. Am. Met. Soc., doi:10.1175/BAMS-D-12-00227.1.