WMOD00526

• Title: Quality Control and Archiving of Digital Data Gathered by the Bureau of Reclaimation's Weather Radar
• Date: 12/12/1989
• Weather Modification - Doc Type: Report

1336

JOURNAL OF APPLIED METEOROLOGY

VOLUME 28

Quality Control and Archiving of Digital Data Gathered by the Bureau
of Reclamation's Weather Radar

GERARD E. KLAZURA t AND RA AMAN* *
Bureau of Reclamation, Denver, Colorado
5 December 1988, and 13 July 1989

ABSTRACT

This paper describes the logic and procedures used to process high volumes of digital radar data recorded on
magnetic tape to a compressed, qua1ity-checked archival format. The basic philosophy in the processing is to
retain all echo data that exceed the background noise threshold, and to convert fixed-length raw data records
to a space-saving variable-length format, having about 70 data quality conditions checked and flagged in binary
masks. Edit flags provide information to analysts regarding errors or potential errors within the header fields
(e.g. azimuth, elevation, date, time, range delay, range interval, and samples per averaged return) and data
fields (e.g. suspicious reflectivity gradients, anomalously high reflectivities, and reflectivities significantly below
the noise threshold).

1. Introduction

This paper describes the logic and procedures used
to process high volumes of digital radar data recorded
on magnetic tape to a compressed, quality-checked ar-
chival format. Computer programs to perform these
functions have been developed and tested. The basic
philosophy in the processing is to retain all echo data
that exceed the background noise threshold, and to
convert fixed-length raw data records to a space-saving
variable-length format, having about 70 data quality
conditions checked and flagged in binary masks. Edit
flags provide information to analysts regarding errors
or potential errors within the header fields (e.g., azi-
muth, elevation, date, time, range delay, range interval,
and samples per averaged return) and data fields (e.g.,
suspicious reflectivity gradients, anomalously high re-
flectivities, and reflectivities significantly below the
noise threshold).
The radar is an incoherent, reflectivity-only system
with a 5-cm wavelength and a 10 beamwidth. The radar
characteristics and earlier processing procedures are
described in Schroeder and Klazura ( 1978). This paper
updates the changes in processing that have occurred
since then.

t Present Affiliation: NEXRAD Operational Support Facility
* * Contractor computer programmer.

Corresponding author address: Gerard Klazura, NEXRAD Op-
erational Support Facility, W jJSxl, 1200 Westheimer Drive, Nor-
man, OK 73069.

2. Data acquisition and flow

a. Data acquisition

Data are generally recorded in a volume scan mode.
A typical volume scan is a sequence of 3600 azimuthal
sweeps starting at lOin elevation and ending at 120 to
200 in elevation, with elevation steps of 10. The time
interval for a complete volume scan is about 2.5 to 5
minutes depending on the total number of 3600 azi-
muthal sweeps and the rotational speed of the antenna.
The antenna azimuthal sweep rate is controlled by the
pulse repetition frequency (PRF) setting, the number
of pulse samples per averaged return (SA), and the
azimuth increment (AI). The PRF is typically 414 s -[;
AI is 1.00; and the SA is 16 or 8, which translates to a
sweep duration (one antenna rotation) of 19 sand 9.5
s, respectively. Echo power returned from targets is
digitized and averaged with other returned signals at
the same space interval in a digital video integrator
and processor (DVIP). A DVIP number (0 to 255),
which is the returned power in counts, is assigned to
each of 250 range-bins, with the largest numbers rep-
resenting the strongest returned signals. Actually, the
lowest DVIP values assigned, which represent returned
signals not detectable in the receiver (i.e., below
threshold), are not equal to zero, but rather are usually
set in the range of 20 to 45.
A "blue sky" elimination feature is included in the
radar's microprocessor /hardware system so that only
records containing at least one radial with at least one
of the 250 range bin DVIP values above a preset
threshold level are recorded. The first and last records
of a constant elevation sweep are always recorded to
maintain an accurate antenna sweep history.