PrecipAccum

PrecipAccum calculates accumulated precipitation from radar files.

Overview

PrecipAccum calculates accumulated precipitation from radar files in MDV format. Precipitation is obtained either from previously-estimated rain rates or estimated from the reflectivity field. Note: we recommend the use of RateAccum over PrecipAccum as RateAccum has a better parameter structure.

Prerequesites

The following items are required:

• Radar data (MDV format)

Parameter file

PrecipAccum uses one parameter file that includes the basic parameters related to data location and field names, which is similar to the parameter files for the other Radx applications.

Ensure file is up to date

To obtain the default parameter file, use the following command:

/path/to/lrose/install/bin/PrecipAccum -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/PrecipAccum -params orig_param_file_name -print_params > new_param_file_name

Important parameters

Program modes of operation

• 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 data

• input_rdata_dir: directory containing radar data in MDV format (if not specified on the command line and if mode = REALTIME)
• dbz_field_name: name of dBZ field in input MDV fields (if empty, dbz_field parameter used instead)
• dbz_field: dBZ field position in input MDV files (integer)
• input_is_rate: tells application whether input data is precipitation rate (mm/hr) instead of dBZ
• input_is_precip: tells application whether input data is precipitation depth (mm) instead of dBZ
• precip_field_name: name of precipitation field in input files (used if input_is_precip is TRUE)

Accumulation method

• accum_method: select the desired type of accumulation method (e.g., running, from time of day, total period)

Precip estimation

• vert_method: method for computing the dBZ value from the vertical column data
• composite_min_altitude: minimum height over which to compute the dBZ value (to use reflectivity at a single height, set equal to composite_max_altitude)
• composite_max_altitude: maximum height over which to compute the dBZ value (to use reflectivity at a single height, set equal to composite_min_altitude)
• low_dbz_threshold: reflectivity below this threshold will be ignored to prevent clear air returns from creating areas of precipitation
• hail_dbz_threshold: reflectivity above this threshold will be assumed to be hail and will be truncated prior to computing the precipitation rate

Output data

• output_precip_dir: files will be written to this directory in MDV format

Running PrecipAccum

To check all command line options for PrecipAccum, including debugging options and file paths, type the following command into a terminal.

/path/to/lrose/install/bin/PrecipAccum -h

Once your parameter file is complete, use a command similar to the following to run the application:

/path/to/lrose/install/bin/PrecipAccum -params param_file_name