Difference between revisions of "RadxPid"
From Lrose Wiki
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RadxPid produces three-dimensional fields of the NCAR particle identification (PID). | RadxPid produces three-dimensional fields of the NCAR particle identification (PID). | ||
| − | = Prerequesites = | + | === Prerequesites === |
The following items are required: | The following items are required: | ||
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* Three parameter files to run RadxPid, calculate KDP, and PID. | * Three parameter files to run RadxPid, calculate KDP, and PID. | ||
| − | = Overview = | + | === Overview === |
RadxPid ingests polarimetric data to estimate the dominant hydrometeor type using NCAR’s Particle Identification algorithm. First, KDP is calculated from PHIDP using the same KDP-specific parameter file as RadxKdp. Next, the polarimetric radar data and calculated KDP are combined with sounding data to determine the most likely dominant hydrometeor. The user decides whether or not the algorithm will use the raw Zh and Zdr data from the radar or correct for attenuation. Finally, the resulting three-dimensional PID categories are sent to an output file. | RadxPid ingests polarimetric data to estimate the dominant hydrometeor type using NCAR’s Particle Identification algorithm. First, KDP is calculated from PHIDP using the same KDP-specific parameter file as RadxKdp. Next, the polarimetric radar data and calculated KDP are combined with sounding data to determine the most likely dominant hydrometeor. The user decides whether or not the algorithm will use the raw Zh and Zdr data from the radar or correct for attenuation. Finally, the resulting three-dimensional PID categories are sent to an output file. | ||
| − | = PID thresholds file = | + | === PID thresholds file === |
These thresholds describe the membership functions for each combination of the PID category and polarimetric field as well as the variable weights for each particle type. The file also contains a place to enter a sounding, if the radar files cover a narrow time period; otherwise, the sounding will be overwritten by data provided by the user, which is explained below. The particle types are most sensitive to temperature, Zh, Zdr, and the standard deviations of Zdr and PhiDP. | These thresholds describe the membership functions for each combination of the PID category and polarimetric field as well as the variable weights for each particle type. The file also contains a place to enter a sounding, if the radar files cover a narrow time period; otherwise, the sounding will be overwritten by data provided by the user, which is explained below. The particle types are most sensitive to temperature, Zh, Zdr, and the standard deviations of Zdr and PhiDP. | ||
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|} | |} | ||
| − | = Sounding data = | + | === Sounding data === |
If sounding data varies in time, sounding data in a non-gridded data format (SPDB) will need to be ingested. SPDB data can come from either observations or numerical simulations (e.g., RAP or HRRR). For additional information regarding this data format, please see the documentation here ('''insert link when written'''). | If sounding data varies in time, sounding data in a non-gridded data format (SPDB) will need to be ingested. SPDB data can come from either observations or numerical simulations (e.g., RAP or HRRR). For additional information regarding this data format, please see the documentation here ('''insert link when written'''). | ||
| − | = Parameter files = | + | === Parameter files === |
RadxPid uses three 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 applications. The second includes the parameters that set the filtering length, method, and relevant coefficients necessary to calculate KDP and estimate attenuation. The third specifies filter parameters and relevant information related to the soundings used by the PID. | RadxPid uses three 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 applications. The second includes the parameters that set the filtering length, method, and relevant coefficients necessary to calculate KDP and estimate attenuation. The third specifies filter parameters and relevant information related to the soundings used by the PID. | ||
| − | == 1) Main parameter file == | + | ==== 1) Main parameter file ==== |
| − | === Ensure file is up to date === | + | ===== Ensure file is up to date ===== |
To obtain the default parameter file, use the following command: | To obtain the default parameter file, use the following command: | ||
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<code lang="bash">/path/to/lrose/install/bin/RadxPid -params orig_param_file_name -print_params > new_param_file_name</code> | <code lang="bash">/path/to/lrose/install/bin/RadxPid -params orig_param_file_name -print_params > new_param_file_name</code> | ||
| − | === Important parameters === | + | ===== Important parameters ===== |
Input params | Input params | ||
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* output_format: select the preferred file type (usually CFRADIAL) | * output_format: select the preferred file type (usually CFRADIAL) | ||
| − | == 2) KDP-specific parameter file == | + | ==== 2) KDP-specific parameter file ==== |
| − | === Ensure file is up to date === | + | ===== Ensure file is up to date ===== |
To obtain the default parameter file, use the following command: | To obtain the default parameter file, use the following command: | ||
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<code lang="bash">/path/to/lrose/install/bin/RadxPid -params_kdp orig_param_file_name -print_params_kdp > new_param_file_name</code> | <code lang="bash">/path/to/lrose/install/bin/RadxPid -params_kdp orig_param_file_name -print_params_kdp > new_param_file_name</code> | ||
| − | === Important parameters === | + | ===== Important parameters ===== |
Unfolding and filtering | Unfolding and filtering | ||
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* KDP_psob_method: Method to handle PSOB | * KDP_psob_method: Method to handle PSOB | ||
| − | == 3) PID-specific parameter file == | + | ==== 3) PID-specific parameter file ==== |
| − | === Ensure file is up to date === | + | ===== Ensure file is up to date ===== |
To obtain the default parameter file, use the following command: | To obtain the default parameter file, use the following command: | ||
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<code lang="bash">/path/to/lrose/install/bin/RadxPid -params_pid orig_param_file_name -print_params_pid > new_param_file_name</code> | <code lang="bash">/path/to/lrose/install/bin/RadxPid -params_pid orig_param_file_name -print_params_pid > new_param_file_name</code> | ||
| − | === Important parameters === | + | ===== Important parameters ===== |
NCAR PID Method | NCAR PID Method | ||
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* PID_sounding_spdb_url: path to SPDB sounding data | * PID_sounding_spdb_url: path to SPDB sounding data | ||
| − | = Running RadxPid = | + | === Running RadxPid === |
To check all command line options for RadxPid, including debugging options and file paths, type the following command into a terminal. | To check all command line options for RadxPid, including debugging options and file paths, type the following command into a terminal. | ||
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<code lang="bash">/path/to/lrose/install/bin/RadxPid -f /path/to/cfradial/files/ -params param_file_name</code> | <code lang="bash">/path/to/lrose/install/bin/RadxPid -f /path/to/cfradial/files/ -params param_file_name</code> | ||
| − | = Other relevant items = | + | === Other relevant items === |
| − | == Additional parameters to edit == | + | ==== Additional parameters to edit ==== |
Caution: this is not an exhaustive list. We urge each user to read through the entire parameter file carefully. | Caution: this is not an exhaustive list. We urge each user to read through the entire parameter file carefully. | ||
| − | === Main parameter file === | + | ===== Main parameter file ===== |
Specifying copy-through fields | Specifying copy-through fields | ||
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* copy_selected_input_fields_to_output: determines whether original fields are copied to the output file | * copy_selected_input_fields_to_output: determines whether original fields are copied to the output file | ||
| − | === KDP-specific parameter file === | + | ===== KDP-specific parameter file ===== |
Precip-induced attenuation correction for DBZ and ZDR | Precip-induced attenuation correction for DBZ and ZDR | ||
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* KDP_specify_coefficients_for_attenuation_correction: the user can either set the coefficients themselves or use the default coefficients based on the radar wavelength | * KDP_specify_coefficients_for_attenuation_correction: the user can either set the coefficients themselves or use the default coefficients based on the radar wavelength | ||
| − | === PID-specific parameter file === | + | ===== PID-specific parameter file ===== |
Computing PID | Computing PID | ||
Revision as of 20:46, 11 January 2021
RadxPid produces three-dimensional fields of the NCAR particle identification (PID).
Contents
Prerequesites
The following items are required:
- Polarimetric radar data (any Radx supported format, e.g., cfradial)
- PID fuzzy logic thresholds file
- Sounding data (either from observations or a numerical model)
- Three parameter files to run RadxPid, calculate KDP, and PID.
Overview
RadxPid ingests polarimetric data to estimate the dominant hydrometeor type using NCAR’s Particle Identification algorithm. First, KDP is calculated from PHIDP using the same KDP-specific parameter file as RadxKdp. Next, the polarimetric radar data and calculated KDP are combined with sounding data to determine the most likely dominant hydrometeor. The user decides whether or not the algorithm will use the raw Zh and Zdr data from the radar or correct for attenuation. Finally, the resulting three-dimensional PID categories are sent to an output file.
PID thresholds file
These thresholds describe the membership functions for each combination of the PID category and polarimetric field as well as the variable weights for each particle type. The file also contains a place to enter a sounding, if the radar files cover a narrow time period; otherwise, the sounding will be overwritten by data provided by the user, which is explained below. The particle types are most sensitive to temperature, Zh, Zdr, and the standard deviations of Zdr and PhiDP.
Set this to a file suitable for the radar transmit mode and wavelength:
| Wavelength | Transmit mode | thresholds_file_example |
|---|---|---|
| S-band | Simultaneous | pid_thresholds.sband.shv |
| S-band | Alternating | pid_thresholds.sband.alt |
| C-band | Simultaneous | pid_thresholds.cband.shv |
| X-band | Simultaneous | pid_thresholds.xband.shv |
Sounding data
If sounding data varies in time, sounding data in a non-gridded data format (SPDB) will need to be ingested. SPDB data can come from either observations or numerical simulations (e.g., RAP or HRRR). For additional information regarding this data format, please see the documentation here (insert link when written).
Parameter files
RadxPid uses three 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 applications. The second includes the parameters that set the filtering length, method, and relevant coefficients necessary to calculate KDP and estimate attenuation. The third specifies filter parameters and relevant information related to the soundings used by the PID.
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/RadxPid -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/RadxPid -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 DBZ
- VARIABLE_field_name: tells RadxPid the polarimetric variable names in the ingested cfradial files
- LDR_available: determines if LDR data is in the file
Computing KDP
- KDP_params_file_path: path to the KDP-specific parameter file
Computing PID
- PID_params_file_path: file path for the PID-specific parameter file
- PID_use_attenuation_corrected_fields: determines whether PID uses Z and ZDR fields that are corrected for attenuation
Writing the output files
- output_dir: files will be written to this directory
- output_format: select the preferred file type (usually CFRADIAL)
2) KDP-specific parameter file
Ensure file is up to date
To obtain the default parameter file, use the following command:
/path/to/lrose/install/bin/RadxPid -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/RadxPid -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 PHIDP
Handling phase shift on backscatter (PSOB)
- KDP_psob_method: Method to handle PSOB
3) PID-specific parameter file
Ensure file is up to date
To obtain the default parameter file, use the following command:
/path/to/lrose/install/bin/RadxPid -print_params_pid > 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/RadxPid -params_pid orig_param_file_name -print_params_pid > new_param_file_name
Important parameters
NCAR PID Method
- pid_thresholds_file_path: file path for the PID thresholds file
Sounding input for PID temperatures
- use_soundings_from_spdb: tells RadxPid whether to override the sounding in the pid thresholds file with SPDB data
- PID_sounding_spdb_url: path to SPDB sounding data
Running RadxPid
To check all command line options for RadxPid, including debugging options and file paths, type the following command into a terminal.
/path/to/lrose/install/bin/RadxPid -h
Once your parameter file is complete, use a command similar to the following to run the application:
/path/to/lrose/install/bin/RadxPid -params param_file_name
The user can also specify the location of cfradial files in the following manner:
/path/to/lrose/install/bin/RadxPid -f /path/to/cfradial/files/ -params param_file_name
Other relevant items
Additional parameters to edit
Caution: this is not an exhaustive list. We urge each user to read through the entire parameter file carefully.
Main parameter file
Specifying copy-through fields
- copy_selected_input_fields_to_output: determines whether original fields are copied to the output file
KDP-specific parameter file
Precip-induced attenuation correction for DBZ and ZDR
- KDP_specify_coefficients_for_attenuation_correction: the user can either set the coefficients themselves or use the default coefficients based on the radar wavelength
PID-specific parameter file
Computing PID
- PID_snr_threshold: mininmum SNR required for the PID to be calculated
- PID_min_valid_interest: mininimum interest value required in order for a PID category to be accepted
- PID_apply_median_filter_to_VARIABLE: determines whether RadxPid applies a filter to specific polarimetric variables before running the PID
- PID_ngates_for_sdev: sets the number of gates used to calculate the standard deviations of ZDR and PHIDP
Sounding input for PID temperatures
- sounding_search_time_margin_secs: the maximum allowable time difference between the radar files and sounding data
- sounding_location_name: directs RadxPid to the appropriate sounding
- sounding_required_pressure_range_hpa: sets the minimum pressure range required for a valid sounding
- sounding_required_height_range_m: sets the minimum altitude range required for a valid sounding