/ht-minimal

Primary LanguagePython

Quickstart

Prerequisites:

  • A compiled version of LibRadTran. Make sure to compile it in a separate conda environment (or in your native OS environment); it will not compile if python is pointing to python3 instead of python2, as is the case with this conda environment. Note that LibRadTran does not have to be installed on the PATH -- just compiled; e.g. I configured it with (from inside the LibRadtran directory) ./configure --prefix=$PWD and just make (not make install).
  • The latest version of Isofit, patched with @ashiklom's fixes for LibRadTran. The recommendation is to install this inside your hypertrace-specific conda environment.

Template files:

  • template.json -- The Isofit template configuration. Specific sections of this will be overwritten by the isofit-workflow.py script, but in general, this should be a complete Isofit JSON configuration file. See isofit/test/data/config_forward.json and isofit/test/data/config_inversion.json from the Isofit repository for some examples.
  • data/lrt_template.inp -- A complete LibRadTran template file. Similar to template.json, this will be only slightly modified by the Python script (only the string formatting templates {aerosol_visibility} and {h2o_mm}), so it should be otherwise self-sufficient. In particular, you may need to modify the source solar path -- the default is relative to the $LIBRADTRAN_DIR/test directory, but an absolute path may be safer.

Configuration file (config.json): A JSON file with the following fields:

  • atmospheres -- List of LibRadTran atmospheres over which to iterate
  • dates -- List of dates over which to iterate (e.g. ["2017-06-01", "2017-08-01"])
  • times -- List of times over which to iterate, as strings with format "HHMM" (e.g. ["0900", "1700"])
  • vzen -- List of view (instrument) zenith angles, in degrees, to iterate over (numeric) (e.g. [0, 30])
  • outdir -- The output directory, as a string
  • reflectance_file -- The true input reflectance file
  • env (optional) -- A named list of environment variables to pass to Isofit. The most important one is probably LIBRADTRAN_DIR, which points to the directory where your libradtran installation is located.

Executing a workflow involves two steps:

  • Run python isofit-workflow.py to generate the Isofit configuration files
  • Run bash <outdir>/run_all.sh script to actually execute the workflow. Note that this uses native bash background process syntax (&) to run workflows in parallel over as many cores as are available.

General uncertainty propagation workflow

Forward model

Go from surface reflectance to top-of-atmosphere radiance. A complete example is in forward.json. Needs the following components:

  • output
    • simulated_measurement_file -- Path to target output file. All parent directories must exist -- they will not be created automatically.
  • forward_model
    • instrument
      • integrations -- Number of integrations (default = 1) ???
      • wavelength_file -- Instrument wavelength file. Plain-text file with two columns, separated by spaces: wavelength (μm or nm) and FWHM
      • SNR, parametric_noise_file, pushbroom_noise_file, NEDT_noise_file -- Instrument noise characteristics. Either a single SNR value or a path to the file with corresponding coefficients.
    • surface
      • reflectance_file -- Path to a file containing measured surface reflectance, which will be converted to TOA radiance
    • radiative_transfer
      • libradtran_vswir (if using Libradtran)
        • wavelength_file -- Wavelengths to simulate (??)
        • libradtran_directory -- Path to libradtran source code
        • libradtran_template_file -- Path to libradtran template file
        • lut_path -- Target directory for RTM look-up tables (LUTs) (dir must already exist)
        • lut_names -- Character array of names of variables in look-up tables. Typically ["H2OSTR", "AOT550"]
        • statevector_names -- The corresponding names of variables in the statevector. For LibRadtran, should be the same as lut_names
  • inversion:
    • simulation_mode: Whether or not to do forward simulation. Here, this should be true
    • windows: Inversion wavelength windows. List of length-2 lists. Usually [[400, 1300], [1450, 1780], [1950, 2450]].