24 Nov 2022
 | 24 Nov 2022
Status: a revised version of this preprint is currently under review for the journal AMT.

Broadband Radiative Quantities for the EarthCARE Mission: The ACM-COM and ACM-RT Products

Jason Neil Steven Cole, Howard W. Barker, Zhipeng Qu, Najda Villefranque, and Mark W. Shephard

Abstract. The EarthCARE satellite mission’s objective is to retrieve profiles of aerosol and water cloud physical properties from measurements made by its cloud-profiling radar, backscattering lidar, and passive multi-spectral spectral imager (MSI). These retrievals, together with other geophysical properties, are input into broadband (BB) radiative transfer (RT) models that predict radiances, and fluxes, commensurate with measurements made, and inferred from, EarthCARE’s BB radiometer (BBR). The scientific goal is that modelled and “observed” BB fluxes differ, on average, by less than ±10 W m-2. When sound synergistic retrievals from the ACM-CAP process are available, they are acted on by the RT models. When they are not available, the RT models act on “composite” atmospheric profiles of retrievals from individual sensors. “Compositing” is performed in the ACM-COM process as described in this report.

The majority of this report describes the RT models, and their products, that make-up Earth-CARE’s ACM-RT process. Shortwave (SW) and longwave (LW) flux and heating rate (HR) profiles are computed by 1D RT models for each ~1 km nadir column of inferred properties. 3D RT models compute radiances for the BBR’s three viewing directions, with the SW model also computing flux and HR profiles; the 3D LW model produces upwelling flux at just one level. All 3D RT products are averages over 5 x 21 km “assessment domains” that are constructed using MSI data. A subset of ACM-RT’s products is passed forward to the “radiative closure assess-ment” process that quantifies, for each assessment domain, the likelihood that EarthCARE’s goal has been achieved. As EarthCARE represents the first mission to make “operational” use of 3D RT models, emphasis in this report is placed on differences between 1D and 3D RT results. For upwelling SW flux at 20 km altitude, 1D and 3D values can be expected to differ by more than EarthCARE’s scientific goal of ±10 W m-2 at least 50 % of the time.

Jason Neil Steven Cole et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'A unique approach to testing quality of cloud retrievals', Anonymous Referee #1, 14 Dec 2022
  • RC2: 'Comment on amt-2022-304', Anonymous Referee #2, 14 Jan 2023

Jason Neil Steven Cole et al.

Data sets

Enhanced 3D radiative transfer ACM-RT calculations and output for Cole et al., 2022 Cole, Jason N. S., Barker, Howard W., Qu, Zhipeng, Villefranque, Najda, & Shephard, Mark W.

Jason Neil Steven Cole et al.


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Short summary
Measurements from the EarthCARE satellite mission will be used to retrieve profiles of cloud and aerosol properties. These retrievals are combined with auxiliary information about surface properties and atmospheric state, e.g., temperature and water vapor. This information allows computation of solar and thermal radiative fluxes and radiances for small domains. These computations can then be compared with co-incident radiometer observations to continually assess EarthCARE retrievals.