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Atmospheric LUT Generator

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Atmospheric Radiative Transfer models (RTMs) have become important tools for the analysis and processing of optical Earth observation data, providing meaningful links between radiometry and atmospheric composition for applications, such as aerosol radiative forcing, air quality, and atmospheric correction. However, the complexity of these RTMs limit their use and applicability for the broader scientific community.

The Atmospheric Look-up table Generator (ALG) toolbox is a standalone software package that can be used independently of ARTMO. ALG allows generating and analyzing look-up tables based on a suite of atmospheric RTMs, facilitating consistent and intuitive user interaction, thereby streamlining model setup, running and storing RTM data for any spectral configuration in the optical domain.
 

ALG's modular architecture.

 

Principally, ALG allows users to:
  • Configure and run atmospheric RTMs in an intuitive way through a single graphical user interface with input options to insert single values or value ranges. This includes the definition of multiple combinations of key input atmospheric (e.g., aerosol-related, gas concentration profiles, clouds) and geometric (e.g., sensor height, surface height, illumination/viewing angles) variables.
  • Couple atmospheric RTMs with several atmospheric databases (Aeronet, OPAC, CAMS, HITRAN, NCEP, Wyoming Radiosondes)
  • Set the spectral range and resolution of the output RTM data at non-contiguous spectral intervals.
  • Run efficiently parallel executions of multiple instances of an atmospheric RTM as a third-party software. Note: ALG toolbox does not provide the compiled nor the source-code of the atmospheric RTM third-party software.
  • Process and store a massive quantity of spectral output data based on a look-up table (LUT) approach in a relational database.

ALG's v3.2 graphical user interface.

The broader scientific community can subsequently use ALG for a wide variety of applications such as: atmospheric correction, cross-comparison of atmospheric RTMs, forward simulation, and sensitivity analysis.

 

Novelties:

This table provides an overivew of ALG's novelties starting from 23 June 2017.

Date

Version

Novelties
23/06/2017 1.0 (beta)
  • ALG v.1.0 (beta) released, supporting the use of MODTRAN v. 5.2 and OPAC v. 3.1.
  • ALG allows users to generate LUTs for gridded data and scattered data based on Latin Hypercube Sampling distribution.
07/07/2017 1.1
  • ALG now supports the use of 6SV v. 2.1 scalar output data (i.e., no polarization).
  • The user can define and store spectral configurations of optical instruments. A set of pre-defined spectral configurations are available: FLORIS (FLEX), MSI (Sentinel-2), OLCI and SLSTR (Sentinel-3) and SeoSAT.
  • ALG now allows users to generate LUTs for scattered data based on Sobol and Halton distributions.
26/12/2019 1.2
  • ALG now allows users to automatically generate LUTs with an optimum distribution of LUT nodes based on the gradient evaluation of the unleryling RTM function.
  • ALG provides a function for the multi-dimensional interpolation of gridded and scattered LUT data. The interpolation methods are: nearest neightbor, linear, piece-wise splines (only for gridded data) and (modified) Shepard's method (Lukaszyk et al., 2004).
  • A bug was identified and resolved regarding the use of MODTRAN at a spectral sampling of 0.1 cm-1.
08/08/2019 2.0
  • New models are now compatible with ALG: MODTRAN6 and libRadtran (in mode Disort)
  • An Aerosol Toolkit (v 1.0.0) has been included to store user-defined aerosol properties. It currently works with 6SV, MODTRAN5 and MODTRAN6.
  • ALG now allows to insert user-defined atmospheric profiles in LUTs for the models MODTRAN5 and MODTRAN6.
  • Users can re-use the distribution of LUT nodes from a previously generated LUT.
  • A new MODTRAN interrogation technique was included in ALG based on the work of Verhoef and Bach 2003.
  • MODTRAN transmission mode has been included in ALG. Users can now make LUTs of gaseous transmittance.
06/01/2020 2.1
  • Users can now run libRadtran in the “gas transmission” mode, based on the direct transmission output of libRadtran with the two-stream solver.
  • An Atmosphere Generator Toolkit (v 1.0.0) has been included to store user-defined atmospheric profiles. It currently works with 6SV, MODTRAN5, MODTRAN6 and libRadtran.
  • A Plotting tool (v 1.0.0) has been included in ALG v2.1 to visualize various input and output files related with ALG (e.g. LUT, OPAC files, 6SV Mie files, user-defined aerosol database).
  • Some minor bugs were corrected.
  • Help system is updated to reflect the changes in ALG v2.1.
30/12/2020 3.0

Changes with respect previous version:

  • ALG’s graphical user interface has been renewed and adapted to the latest Matlab R2020b App Designer tool.
  • Users can now read the LUT node distribution from an external .txt file.
  • A user-defined random distribution option has been added into ALG v3.0. Users can now distribute the values of the input variables following a given probability distribution (Gaussian or Log-Normal).
  • A TOA radiance mode (only for Lambertian surface) is now available with MODTRAN, 6SV and libRadtran.
  • The Verhoef and Bach 2012 MODTRAN interrogation technique has been added.
  • ALG is now compatible with the polradtran solver in libRadtran.
  • For Windows users, the compatibility of libRadtran with ALG is now possible with Ubuntu for Windows instead of the previous Cygwin.
  • The Atmosphere Generator Toolkit (v 1.0.1) has been updated to be compatible with NWP SAF atmospheric profiles database.
  • A Plotting tool (v 1.0.1) has been updated to visualize ­atmospheric profiles data.
  • Some minor bugs were corrected.
  • Help system is updated to reflect the changes in ALG v3.0.
31/08/2021 3.1
  • ALG is now compatible with two new open-source models: ARTDECO and SBDART. Windows users can run these models using Ubuntu for Windows (see ALG Help/user guide).
  • ALG allows you now to run your radiative transfer models on an external Linux server. Note: this functionality is not documented. Please contact us if you want to use it.
  • Minor bugs have been corrected, particularly occurring when porting ALG’s GUI to the newest Matlab R2020b app designer tool.
 22/08/2023  3.2
  • RAMI4ATM tool automates the generation and processing of atmospheric RTM data ready for the RAMI4ATM activity.
  • A Surface spectral library tool is implemented to allow users to include their own Lambertian and BRDF models for the TOA radiance execution mode.
  • The updated TOA radiance mode allows users to use built-in BRDF models within each atmospheric RTM.
  • Distribution of LUT points can now be done based on natural distributions, including correlations from existing atmospheric/climatological datasets.
  • LUTs can now be generated at a sensor spectral configuration.
  • The Atmosphere Generator tool now interfaces with the HITRAN database using HAPI (this is still ongoing so be aware of potential errors).
  • Some minor bugs have been fixed.