Difference between revisions of "RadxKdp"
From Lrose Wiki
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| − | RadxKdp ingests polarimetric radar data and calculates <math>K_{DP}</math> from | + | RadxKdp ingests polarimetric radar data and calculates <math>K_{DP}</math> from <math>\phi_{DP}</math>. |
=== '''Prerequesites''' === | === '''Prerequesites''' === | ||
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* Polarimetric radar data (any Radx supported format, e.g., cfradial) | * Polarimetric radar data (any Radx supported format, e.g., cfradial) | ||
| − | * Two parameter files to run RadxKdp and to calculate | + | * Two parameter files to run RadxKdp and to calculate <math>K_{DP}</math>. |
=== '''Overview''' === | === '''Overview''' === | ||
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| − | ''A more detailed explanation of the procedure used to estimate | + | ''A more detailed explanation of the procedure used to estimate <math>K_{DP}</math> can be found [http://wiki.lrose.net/index.php/KDP_estimation here].'' |
''Information about how attenuation is estimated from <math>K_{DP}</math> can be found [http://wiki.lrose.net/index.php/Estimated_Attenuation here].'' | ''Information about how attenuation is estimated from <math>K_{DP}</math> can be found [http://wiki.lrose.net/index.php/Estimated_Attenuation here].'' | ||
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Input field information | Input field information | ||
| − | * SNR_available: determines if SNR data is in the file or needs to be calculated from | + | * SNR_available: determines if SNR data is in the file or needs to be calculated from <math>Z_H</math> |
* VARIABLE_field_name: tells RadxKdp the polarimetric variable names in the ingested cfradial files | * VARIABLE_field_name: tells RadxKdp the polarimetric variable names in the ingested cfradial files | ||
Computing KDP | Computing KDP | ||
| − | * KDP_params_file_path: path to the | + | * KDP_params_file_path: path to the <math>K_{DP}</math>-specific parameter file |
Output format | Output format | ||
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* output_dir: files will be written to this directory | * output_dir: files will be written to this directory | ||
| − | ==== '''2) | + | ==== '''2) <math>K_{DP}</math>-specific parameter file''' ==== |
===== '''Ensure file is up to date''' ===== | ===== '''Ensure file is up to date''' ===== | ||
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Unfolding and filtering | Unfolding and filtering | ||
| − | * KDP_fir_filter_len: Filter length applied to | + | * KDP_fir_filter_len: Filter length applied to <math>\phi_{DP}</math> |
Handling phase shift on backscatter (PSOB) | Handling phase shift on backscatter (PSOB) | ||
Revision as of 21:06, 23 February 2021
RadxKdp ingests polarimetric radar data and calculates [math]\displaystyle{ K_{DP} }[/math] from [math]\displaystyle{ \phi_{DP} }[/math].
Contents
Prerequesites
The following items are required:
- Polarimetric radar data (any Radx supported format, e.g., cfradial)
- Two parameter files to run RadxKdp and to calculate [math]\displaystyle{ K_{DP} }[/math].
Overview
RadxKdp uses a couple different methods to calculate [math]\displaystyle{ K_{DP} }[/math] from PHIDP. In general, [math]\displaystyle{ K_{DP} }[/math] is calculated from the PHIDP slope between range gates (after smoothing and unfolding the PHIDP data). Filtering smears out [math]\displaystyle{ K_{DP} }[/math] in range, so an additional field (KDP_SC) is constrained by [math]\displaystyle{ K_{DP} }[/math] estimated theoretically from Z and ZDR.
A more detailed explanation of the procedure used to estimate [math]\displaystyle{ K_{DP} }[/math] can be found here.
Information about how attenuation is estimated from [math]\displaystyle{ K_{DP} }[/math] can be found here.
Parameter files
RadxKdp uses two separate parameter files. The first includes the basic parameters related to data location and field names, which is similar to the parameter files for the other Radx applications. The second includes the parameters that set the filtering length, method, and relevant coefficients necessary to calculate [math]\displaystyle{ K_{DP} }[/math] and estimate attenuation.
1) Main parameter file
Ensure file is up to date
To obtain the default parameter file, use the following command:
/path/to/lrose/install/bin/RadxKdp -print_params > param_file_name
If you already have a parameter file and simply want to check for (and add) updated parameters while retaining current parameters, use the following command:
/path/to/lrose/install/bin/RadxKdp -params orig_param_file_name -print_params > new_param_file_name
Important parameters
Input params
- input_dir: directory containing radar data (if not specified on the command line and if mode = REALTIME)
- mode: determines if the program waits for new files (REALTIME), moves through start and end times specified on the command line (ARCHIVE), or moves through list of files specified on the command line (FILELIST)
Input field information
- SNR_available: determines if SNR data is in the file or needs to be calculated from [math]\displaystyle{ Z_H }[/math]
- VARIABLE_field_name: tells RadxKdp the polarimetric variable names in the ingested cfradial files
Computing KDP
- KDP_params_file_path: path to the [math]\displaystyle{ K_{DP} }[/math]-specific parameter file
Output format
- output_format: select the preferred file type (usually CFRADIAL)
Output directory
- output_dir: files will be written to this directory
2) [math]\displaystyle{ K_{DP} }[/math]-specific parameter file
Ensure file is up to date
To obtain the default parameter file, use the following command:
/path/to/lrose/install/bin/RadxKdp -print_params_kdp > param_file_name
If you already have a parameter file and simply want to check for (and add) updated parameters while retaining current parameters, use the following command:
/path/to/lrose/install/bin/RadxKdp -params_kdp orig_param_file_name -print_params_kdp > new_param_file_name
Important parameters
Unfolding and filtering
- KDP_fir_filter_len: Filter length applied to [math]\displaystyle{ \phi_{DP} }[/math]
Handling phase shift on backscatter (PSOB)
- KDP_psob_method: Method to handle PSOB
Running RadxKdp
To check all command line options for RadxKdp, including debugging options and file paths, type the following command into a terminal.
/path/to/lrose/install/bin/RadxKdp -h
Once your parameter file is complete, use a command similar to the following to run the application:
/path/to/lrose/install/bin/RadxKdp -params param_file_name
The user can also specify the location of cfradial files in the following manner:
/path/to/lrose/install/bin/RadxKdp -f /path/to/cfradial/files/ -params param_file_name