CMAC

CMAC: Corrected Precipitation Radar Moments in Antenna Coordinates

CMAC (Corrected Moments in Antenna Coordinates) is a set of algorithms and code that does corrections to Radar data, but also adds fields to the original data. Using fuzzy logic CMAC also calculates gate IDs such as rain, snow and second-trip. Some other examples of the corrections done are velocity dealiasing and attenuation-corrected reflectivity. Example of fields added are rain_rate_A, velocity_texture and filtered_corrected_differential_phase.

More information can be found at https://arm.gov/data/science-data-products/vaps/cmac

The Atmospheric Community Toolkit is installed in this binder and can be used to download data for CMAC from ARM Data Discovery. For an example on how to download ARM datastreams from Data Discovery, click here.

All ARM files are in the format that is needed by CMAC for processing.

Background

In 2010 the Atmospheric Radiation Measurement (ARM) program procured a number of 3 and 5 cm wavelength scanning radars for documenting the macrophysical, microphysical and dynamical structure of precipitating systems. In order to maximize the scientific impact of these instruments, the program supported the development of an application chain to correct for various propagation and measurement issues so that "point" values of the moments of the radar spectrum and polarimetric measurements could be retrieved.

Because these radars operate at shorter wavelengths than the more common 10 cm (S-band) radars, they are more strongly affected by two-way attenuation as the beam propagates through precipitation, and their shorter maximum unambiguous range leads to more frequent Doppler velocity aliasing. CMAC was built to robustly correct for these effects. Rather than have each processing step make its own conditional decision about where to run based on ad-hoc quality measurements, CMAC first performs a gate-by-gate identification of the dominant scattering process at each radar gate (e.g. rain, snow, melting layer, second-trip echo, or no significant scatterer). This gate ID is performed before any corrections are applied, and is used to construct Py-ART gate filters that determine which corrections and retrievals should be applied at each gate — for example, dealiasing is run on every class except "no significant return", while attenuation correction is only applied to gates classified as rain.

The full application chain includes velocity dealiasing, extraction of propagation differential phase from the measured differential phase, calculation of specific differential phase, calculation and integration of specific attenuation to correct reflectivity, and calculation of rain rate. For the underlying science, motivation and implementation details, see the technical report in documents/technical_document/cmac2p0_technical_report.tex.

Install

CMAC and the required environment can be installed by using the instructions below:

git clone https://github.com/ARM-Development/cmac.git
cd cmac
conda env create -f environment.yml
conda activate cmac_env

If you wish to use the LP phase processing code instead of the CSU code, you will need to set an environment variable to point to the location of the COIN-OR libraries. This can be done by using the following command in the terminal:

export COIN_INSTALL_DIR=/Users/yourusername/youranacondadir/envs/cmac_env

If you are using the Bringi KDP retrieval, method then this is not needed. The Bringi method is the default method for KDP retrieval in CMAC. If you want to use the LP method, then you will need to set the environment variable as described above and then set the kdp_method argument in the config file to 'lp'.

You will need to install Anaconda Compilers for the installation of CyLP. These compilers can be found here and differ between OS: https://docs.conda.io/projects/conda-build/en/latest/resources/compiler-tools.html

After the compilers are installed, you should be able to install CyLP with:

pip install git+https://github.com/coin-or/CyLP.git

Scripts such as cmac_animation and cmac_dask require additional dependencies:

source activate cmac_env
conda install -c menpo ffmpeg=version
conda install dask ipyparallel

Note: For ffmpeg, depending on the user's operating system, the version will need to be replaced with corresponding version number found here:

https://anaconda.org/menpo/ffmpeg

Using CMAC

Once downloaded, CMAC can be used in the terminal. The required positional arguments are radar_file, sonde_file and radar_config (the name of a radar configuration, e.g. bnf_csapr2_ppi, that exists in cmac.default_config or in a YAML file passed via --config-file).

An example:

cmac /home/user/cmac2.0/data/radar_file.nc \
     /home/user/cmac2.0/data/sonde_file.cdf \
     bnf_csapr2_ppi

The script also accepts the following optional arguments:

-c, --config-file PATH

Optional YAML config file whose values override the built-in defaults for the given radar_config.

-cf, --clutter-file PATH

Clutter file to use for addition of the clutter gate id.

-o, --out-radar-directory PATH

Output directory for the CMAC radar file. Defaults to the user home directory.

-id, --image-directory PATH

Directory to save CMAC radar quicklook images. Defaults to the user home directory.

-ma, --meta-append SOURCE

Source of metadata for the output file. config (default) uses the per-radar metadata from cmac.default_config / the YAML override. Pass a path to a JSON file to use custom metadata, or default to use the generic global defaults.

--verbose / --no-verbose

Display debugging output. Defaults to off.

For backwards compatibility, the underscore forms of each long option (e.g. --config_file, --clutter_file, --out_radar_directory, --image_directory, --meta_append) are also accepted.

There is currently a default_config.py file with dictionaries for radars. Additional radars can be added there, or supplied through a YAML file passed via --config-file and selected with the radar_config positional argument. See documents/cmac_config_reference.md for a full description of every section and key in that YAML file.

Documentation

• notebooks/getting_started_with_cmac.ipynb — a walkthrough of downloading a radar file and sounding, running cmac(), and generating quicklooks from a Jupyter notebook.
• documents/cmac_config_reference.md — a reference for every section and key of the YAML config file accepted via config_file / --config-file.
• documents/technical_document/cmac2p0_technical_report.tex — a technical report on the motivation, science and implementation of CMAC2.0.

Lead Developers

• Scott Collis
• Robert Jackson
• Zach Sherman
• Max Grover

Credits

The Bringi KDP retrieval method is taken from CSU-RadarTools, which is a collection of radar processing tools developed by Colorado State University. The CSU-RadarTools can be found at https://github.com/CSU-Radarmet/CSU_RadarTools.