A satellite simulator and retrieval sandbox tool for cloud studies.

S3COM is a tool at the interface of high-resolution modeling and satellite observations. It aims to make cloud studies a little easier by

Simulating realistic satellite observations and cloud products from model outputs
Quantifying the sensitivity of radiative quantities to cloud parameters (in progress)
Assisting the development of retrieval algorithms using output fields from high-resolution models (in progress)

Install

S3COM can be installed via its makefile:

git clone https://github.com/odrans/S3COM.git
cd S3COM
make

More details on this page

Click here for more details on S3COM dependencies and environment.

Dependencies

The following dependencies are needed and require path adjustments in the Makefile:

NetCDF4 (C and Fortran)
- Makefile path: PATH_NETCDF_C, PATH_NETCDF_F
HDF5
- Makefile path: PATH_HDF5
RTTOV
- RTTOV v13 is the main radiative transfer code in S3COM.
- Makefile path: PATH_RTTOV
- Notes:
  - RTTOV can be installed following these instructions. Note that it requires NetCDF4 and HDF5 to be explicitely linked in its build/Makefile.local file before running rttov_compile.sh.
  - Depending on the spectrum of simulated instruments, adequate coefficient files and BRDF / emissivity atlases should be downloaded and included in the RTTOV repository.
  - Following RTTOV recommendations, it is advised to raise the system stack size: ulimit -s unlimited.

All Makefile paths refer to base repositories giving access to libraries, objects and binaries.

Environment

PATH_S3COM should be set in Makefile to indicate where S3COM is installed.

The environment section provides advised settings on specific supercomputers.

Note: Run make clean to remove all built binaries, libraries and objects.

Usage

S3COM requires the path to a namelist file as main argument:

./s3com config_default.nml

The namelist contains information on input and output files as well as important options to run S3COM. Refer to namelist section for a detailed description.

S3COM outputs are 3 files containing satellite simulations, retrievals and atmospheric data. See the output section.

Documentation

A structured documentation is generated by Doxygen. Refer to this technical page for more information. The documentation includes descriptions of all subroutines and modules, with specific examples for usage.

Current limitations

The current version is only configured to handle simulations from the ICON model. Some adjustments will be necessary to use outputs from another model.
S3COM only simulates measurements from passive remote-sensing sensors.
Polarization and 3D effects are not included.

R package

The Rs3com package was developed to conveniently create namelist files, run the algorithm, read its input and output and create basic figures.

Caution

S3COM does not account for sub-grid variability of cloud properties. It should be used on atmospheric model simulations with a spatial resolutions similar or higher than that of the selected satellite instruments, ideally from CRMs or LES models. It is advised against using S3COM on GCM outputs; for such use we advise more dedicated satellite simulators, such as COSPv2.

License

S3COM is available under a BSD 3-clause license. See LICENSE for details.