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 the OPAC aerosol database.
  • 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 at input variable window.

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.
On-going 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.