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https://github.com/space-physics/lowtran

LOWTRAN atmospheric absorption extinction, scatter and irradiance model--in Python and Matlab
https://github.com/space-physics/lowtran

atmosphere atmospheric-modelling f2py fortran geoscience lowtran matlab matlab-python-interface python

Last synced: 6 days ago
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LOWTRAN atmospheric absorption extinction, scatter and irradiance model--in Python and Matlab

Host: GitHub
URL: https://github.com/space-physics/lowtran
Owner: space-physics
License: mit
Created: 2015-03-31T19:19:59.000Z (almost 10 years ago)
Default Branch: main
Last Pushed: 2024-04-22T17:56:45.000Z (10 months ago)
Last Synced: 2024-10-29T22:29:36.217Z (4 months ago)
Topics: atmosphere, atmospheric-modelling, f2py, fortran, geoscience, lowtran, matlab, matlab-python-interface, python
Language: Python
Homepage:
Size: 3.16 MB
Stars: 101
Watchers: 9
Forks: 42
Open Issues: 6
Metadata Files:
- Readme: README.md
- License: LICENSE.txt

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README

# Lowtran in Python

[![Zenodo DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.213475.svg)](https://doi.org/10.5281/zenodo.213475)
![Actions Status](https://github.com/space-physics/lowtran/workflows/ci/badge.svg)
[![PyPi Download stats](http://pepy.tech/badge/lowtran)](http://pepy.tech/project/lowtran)

LOWTRAN7 atmospheric absorption extinction model.
Updated to be platform independent and easily accessible from Python and
[Matlab](#matlab).

The main LOWTRAN program is accessible from Python by using direct memory transfers instead of the cumbersome and error-prone process of writing/reading text files.
`xarray.Dataset` high-performance, simple N-D array data is passed out, with appropriate metadata.

## Gallery

See below for how to make these examples.

![Lowtran7 absorption](./gfx/lowtran.png)

## Install

Lowtran requires a Fortran compiler and CMake.
We use `f2py` (part of `numpy`) to seamlessly use Fortran libraries from Python by special compilation of the Fortran library with auto-generated shim code.
For Python 3.12, make sure to install setuptools using pip, i.e., `pip install setuptools` and make sure meson is available on the system.

If a Fortran compiler is not already installed, install Gfortran:

* Linux: `apt install gfortran`
* Mac: `brew install gcc`
* Windows: Windows Subsystem for Linux

Install Python Lowtran code

```sh
pip install -e .
```

## Examples

In these examples, optionally write to HDF5 with the `-o` option.

We present Python [examples](./example) of:

* ground-to-space transmittance: TransmittanceGround2Space.py

![Lowtran Transmission](./doc/txgnd2space.png)
* sun-to-observer scattered radiance (why the sky is blue): ScatterRadiance.py

![Lowtran Scatter Radiance](./gfx/whyskyisblue.png)
* sun-to-observer irradiance: SolarIrradiance.py

![Lowtran Solar Irradiance](./gfx/irradiance.png)
* observer-to-observer solar single-scattering solar radiance (up-going) with custom Pressure, Temperature and partial pressure for 12 species: UserDataHorizontalRadiance.py
![Lowtran Solar Irradiance](./gfx/thermalradiance.png)
* observer-to-observer transmittance with custom Pressure, Temperature and partial pressure for 12 species: UserDataHorizontalTransmittance.py
* observer-to-observer transmittance: HorizontalTransmittance.py

![Lowtran Horizontal Path transmittance](./gfx/horizcompare.png)

### Matlab

Matlab users can seamlessly access Python modules, as demonstrated in
[RunLowtran.m](./RunLowtran.m).

Here's what's you'll need:

1. [Setup Python ↔ Matlab interface](https://www.scivision.dev/matlab-python-user-module-import/).
2. Install Lowtran in Python as at the top of this Readme.
3. From Matlab, verify everything is working by:

```matlab
runtests('lowtran')
```

## Notes

LOWTRAN7
[User manual](http://www.dtic.mil/dtic/tr/fulltext/u2/a206773.pdf)
Refer to this to understand what parameters are set to default.
Currently I don't have any aerosols enabled for example, though it's possible to add them into the code.

Right now a lot of configuration features aren't implemented, please request those you want.

### Reference

* Original 1994 Lowtran7 [Code](http://www1.ncdc.noaa.gov/pub/data/software/lowtran/)
* `LOWFIL` program in reference/lowtran7.10.f was not connected as we had previously implemented a filter function directly in Python.
* `LOWSCAN` spectral sampling (scanning) program in `reference/lowtran7.13.f` was not connected as we had no need for coarser spectral resolution.