Radial Radar/Lidar Data Formats at NCAR


Overview

At NCAR, the following formats in use specifically for radial radar and lidar data:

Software has been developed at NCAR to assist with manipulation of data in these formats:

In addition, FORTRAN and MatLab utilities for dealing with CfRadial format files are currently under development at NCAR.

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Example data sets

Example data sets are available as follows:

Images of selected contents of the data files are available as follows:


CFRADIAL FORMAT

CfRadial is the most recent format to be developed for handling radial data from modern radar and lidar platforms. CfRadial is a collaborative effort between EOL, RAL and UNIDATA.

CfRadial is a CF-compliant netCDF format. Because of its CF-compliance, CfRadial will allow researchers familiar with CF to read the data into a wide variety of analysis tools, models etc.

The CfRadial documentation is available in PDF

See the CfRadial web page for full details.

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DORADE FORMAT

DORADE was developed in the 1990's, to handle the more complex nature of Doppler radars, especially airborne platforms. DORADE is a binary format composed of distinct header and data blocks, making it extensible.

Many NCAR field projects from 1990 to 2010 stored the raw radial radar data, as well as derived products, in DORADE format.

The NCAR/EOL soloii display is a primary tool for displaying, editing and manipulating DORADE files.

From 2010, DORADE files will gradually be replaced with the new CfRadial format.

The DORADE documentation was updated in 2010.

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UNIVERSAL FORMAT

Commonly known as UF, the Universal Format is formally known as the Common Doppler Radar Exchange Format. UF was documented by S.L Barnes in 1980 in the Bulletin of the Americal Meterological Society (BAMS), Vol 61, 1401 - 1404.

UF was primarily designed for access via FORTRAN. A FORTRAN binary block holds the data for each ray (or beam). UF is composed exclusively from ASCII characters and 16-bit integer words. Floating point values are computed by applying scale factors and offsets to the integer values.

UF has some significant limitations. Field names are limited to 2 characters. For example, reflectivity is often referred to as ZH, or DZ, and radial velocity as VR, because the 2-character limitation prevents use of longer names such as DBZ or VEL. Also, the headers are limited in length, so that the metadata associated with more sophisticated radars cannot be accurately represented.

Neverthless, UF is still popular with many researchers, and much analysis code has been written for UF data.

The UF documentation is based on the 1980 BAMS article.

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FORAY netCDF FORMAT

The FORAY Project developed a radar data exchange format based on the Unidata netCDF scientific data format.

FORAY netCDF is based on NetCdf version 3, i.e. it does not support data compression.

The FORAY netCDF sweep file format was the primary format used for the TIMREX field experiment in Taiwan. TIMREX also stored the radial data in DORADE format.

An example ncdump from a FORAY netCDF file is the best way to understand the format.

The FORAY project has now ended. TIMREX will be the only NCAR field project which will use FORAY netCDF files. All subsequent projects will use CfRadial and DORADE.

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IWRF time series format

The IWRF time format was developed to provide a platform-independend data exchange format for time series data.

The IWRF documentation is available in PDF.

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Author: Mike Dixon
EOL, NCAR, P.O.Box 3000, Boulder, CO, 80307-3000
July 2010