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Doppler Meteorological Radar
WSR-88D, hereafter referred to as the WSR-88D, is a standalone system which
detects, processes, distributes, and displays radar weather data. The WSR-88D
uses Doppler radar technology to acquire particle velocity data in addition
to range, direction, and reflectivity data. The WSR-88D is a software-driven
system. Software processing is used to control the radar operating characteristics
to produce the optimum radar volume coverage patterns and to optimize the
radar returns. The resulting base weather data is then processed through
the application of meteorological algorithms to generate base and derived
weather products. These products are further processed using graphics algorithms
to produce readily interpretable weather data displays on color monitors.
The WSR-88D supports the needs of user agencies within the Departments
of Commerce (DOC), Transportation (DOT), and Defense (DOD) for information
on the location, intensity, and movement of both routine and hazardous
weather phenomena. The WSR-88D supplies information on the location, intensity
and movement of both routine and hazardous weather phenomena.
Configuration. Since the WSR-88D supports the needs
of many users, the equipment group locations, equipment complement, equipment
arrangement, and computer programs vary from site to site. As a result,
each WSR-88D installation may be unique. However, in its basic form, the
WSR-88D is functionally subdivided into five equipment groups described
in the following paragraphs.
Radar Data Acquisition (RDA) Group The RDA comprises
the Doppler radar and provides base weather data. The RDA equipment is
always contained in a Radar Equipment Shelter, which is collocated with
a Generator Shelter near the Radar Tower. The Radar Tower supports the
RDA Antenna/Pedestal. The Radar Equipment Shelter may also contain a single
Radar Product Generation (RPG) or two RDA channels and two RPG channels
(redundant configuration).
Wide band Communications (WBC) Group The WBC links
the RDA with the RPG. It uses hardwire, fiber optic, T1 Telephone Connection,
or microwave line of sight (MLOS) communication depending upon whether
the RDA and RPG are physically collocated or in separate locations. If
the RPG is located within 400 feet of the RDA, the WBC is usually a hardwire
connection. If the RPG is located farther away from the RDA, the WBC may
be fiber optic or MLOS. When a MLOS WBC is used, there may be a guyed or
self-supporting MLOS antenna tower and a MLOS Shelter located approximately
400 feet from the Radar Tower. A guyed or self-supporting MLOS antenna
tower may be located at the user's facility. When a MLOS repeater is needed,
an antenna tower is located between the radar site and the user's facility.
Radar Product Generation (RPG) Group The RPG uses
weather algorithms to process the RDA base weather data to produce a variety
of weather data products. System mode control is exercised from the RPG's
Unit Control Position (UCP). The RPG can be collocated with the RDA or
located at the controlling user's PUP site.
Principal User Processing
(PUP) Group The PUP uses display algorithms to format the RPG's weather
products for display as graphics weather maps. The PUP workstation is the
users operating position for the WSR-88D. The PUP is always located at
a user's facility. Usually, there is more than one PUP associated with
an RPG. The PUPs may be located at different user facilities. The RPG may
be collocated with its UCP at the controlling user's PUP , more detailed
description of the collocated RPG, UCP operation). The PUP and RPG equipment
layout at a user's facility is variable. PUPs and RPGs communicate via
narrowband communication links (leased and dial telephone lines). Connection
to the telephone dial system network allows other users and PUPs not associated
with the WSR-88D system site to access weather products from the system.
Real Property Installed Equipment (RPIE) Group.
The RPIE comprises equipment shelters, towers, radome, backup power generation,
and auxiliary functions.
Meteorological Products. To provide users with
real-time weather radar data, the WSR-88D generates weather products which
are presented to operational personnel. Products which depict specific
weather phenomena are available to users in a readily interpretable, graphical
format on color monitors or via a color printer available at the PUP. Base
and derived products depict precipitation, wind and wind shear, tornadoes,
mesocyclones, thunderstorms, turbulence, hail and clear-air phenomena.
Many of the weather products, including hydrological products, are generated
automatically and distributed to users on a routine basis.
Base Products. Base products are generated by the
RPG from reflectivity, mean radial velocity, and spectrum width base data
generated by the RDA and transmitted to the RPG. The RDA resolves range
ambiguities, marks data overlaid by range ambiguities, removes biases caused
by receiver noise, and thresholds the data. The RPG resolves velocity ambiguities
in the mean radial velocity base data prior to generating the base products.
These base products consist of, reflectivity,
mean
radial velocity and
radial
velocity spectrum width. They are generated in several different resolutions
as specified in the product generation list. The base products are Plan
Position Indicator ((PPI-type) constant evaluation "cut" displays when
presented on a color graphics monitor at the PUP.
Derived Products. Derived products are obtained
by processing base data using meteorological, hydrological, and display
processing algorithms resident in the RPG Processor. The derived products,
when displayed on color graphic monitors, depict the data in a form requiring
minimum interpretive effort by the operator. Derived products include both
direct area field and contour presentations of reflectivity, echo tops,
wind shear, and may include annotations of storm cell tracks, mesocyclones,
tornado vortex signatures (TVS), and identified or probable hail locations.
Displays of derived products may collect data from multiple elevation angle
cuts and, in addition to the above symbolic annotations, may include a
variety of annotations generated by the algorithms and indicative of severe
weather. The derived product processing techniques permit the establishment
of detection and alert thresholds for phenomena such as hail, tornados
vortex signatures, and mesocyclones. Such weather alerts are presented
to the operator symbolically on the graphics display monitors and also
by means of an audible alarm located at the PUP operator workstation.
Alphanumeric Products. Alphanumeric products provide
processed radar data for users. They consist of text messages and summary
formats of coded radar observations. The alphanumeric products also provide
the operator with quantitative hard data which may be displayed on a Cathode
Ray Tube (CRT) monitor for immediate evaluation, or generated as hardcopy
by a printer.
Data Array Products. The derived data array products
are used to provide data in a compressed, non displayable format for transmission
to systems external to the WSR-88D for further processing. These products,
which consist of digital data fields and streams, may also be archived
for later processing and analysis.
Users. The users of WSR-88D weather products fall
into two categories: principal users, and other users. The principal users
are agencies within the DOC, DOT and DOD which own, maintain, and operate
the WSR-88D system. They use the processing and display capabilities provided
by the PUP and its associated workstation to support the routine display
of selected current or archival products, the annotation of products, and
the further distribution of products. Products are also distributed through
the Principal Users External System (PUES). Other users are other government
and civilian activities that require weather products. These other users
have access to a limited set of products either directly from the RPG,
or via a PUP. Each RPG has the capability of interfacing with principal
users' data communications networks for transmission of weather radar data
to national, regional, and local forecast offices which are remote from
the RPG. Each RPG also provides the capability for principal and other
users with remote display subsystems to establish a dial-up communication
connection to obtain weather radar data. The equipment provisions required
to establish these connections are, however, the responsibility of the
appropriate user agency. A procedural access method using password protection
and time-out limits is used to allow different groups of users to share
common dial-up interface ports. Users assigned to the same dial-up port
have equal priorities; however, different ports may have different priorities.
Each RPG or PUP has interfaces to local users' data dissemination systems.
Additionally, all WSR-88D sites also provide interfaces for rain gauge
data collection.
The basic WSR-88D system consists of five equipment groups,
which are interconnected to provide the WSR-88D operational requirements.
The five equipment groups are:
RDA Group. The RDA is the Doppler radar subsystem
which generates and radiates RF pulses, then acquires and processes reflected
RF signals to obtain weather radar base data. The base data consists of
measurements of reflectivity,
mean
radial velocity, and
velocity
spectrum width. Base data is available in digital format for archiving
and for transmission to the RPG Group. The RDA is a self-contained unit
designed for continuous, unattended operation. The RDA includes the Radar
Transmitter, Antenna/Pedestal,
Radar
Receiver, and Data Processor Cabinet. The Data Processor Cabinet contains
the associated hardware, firmware, and software required to perform the
signal processing, ground clutter suppression, data extraction, pedestal
control, status monitoring and fault detection, local control and display
of performance data, auto-calibration, and archiving functions related
to the radar operation. The Antenna/Pedestal is housed in a radome on top
of a radar tower, other RDA equipment are housed in the Radar Equipment
Shelter.
WBC Group. The WBC provides high-speed intercomputer
transfer of base data, radar status, and control data between an RDA and
its associated RPG. Depending on the separation distance and local requirements,
the wideband links at a particular site may be a direct wire link for distances
up to 400 ft, a T1 telephone connection for a hardware connection over
400 feet, a fiber optics link (used from 400 ft through 18 km), or a MLOS
link (for distances from 1 km through 40 km for a single-hop link, or beyond
40 km for a multiple-hop link). Both ends of the link (MLOS or fiber optic)
will be mounted in its own cabinet. At the RDA, the MLOS antenna will be
mounted on the Radar Tower or MLOS tower.
At the RPG, the MLOS antenna will be mounted on the facility
roof, existing tower, or on a separate self-supporting tower. Both the
RDA and RPG data processors contain a second (expansion) wideband port.
This optional second wideband link can be used to connect either equipment
group to other external systems.
RPG Group. The RPG receives the base data from
the RDA and processes it to produce base products (reflectivity, mean radial
velocity, and velocity spectrum width). The RPG further processes these
base data using stored algorithms to develop a set of derived meteorological
products. The resulting product set, including the base products, is then
made available for distribution over narrowband communications links to
PUP Groups associated with the RPG, PUES, and to other user systems. The
RPG consists of a Data Processing Cabinet, Communications Cabinet, and
a UCP.
RPG Data Processing RPGDP Cabinet. The RPGDP Cabinet
contains all the hardware and software required for real-time generation
and storage of products for operational use. It also includes the hardware
and software required for system remote control, status monitoring and
error detection, product archiving, and hydro meteorological data processing.
RPG Communications Cabinet. The RPG Communications
Cabinet contains the narrowband links used between the RPG and its associated
PUPs for internal product requests and distribution, for inter-site product
requests and distribution, and for distribution of products to other users.
The narrowband communication links are modem-based serial data links which
are directly interconnected for internal communications, or utilize transmission
over leased or dial-up commercial telephone lines for external data distribution.
UCP.
The UCP consists of a terminal and a line printer. The UCP is used by operators
and maintenance technicians for data entry, program control, and an online
display and data interface for radar mode control. The UCP terminal is
also used for system test and troubleshooting, and local product selection,
generation, and distribution control.
PUP Group. The PUP receives base and derived weather
products from the RPG and provides for the request, display, storage, annotation,
and distribution of products by operational personnel. The PUP consists
of a PUP Data Processor Cabinet,
a PUP Workstation, and a
System Console.
PUP Data
Processor Cabinet. The PUP Data Processor Cabinet contains the
dedicated hardware and software required for
graphics processing, local control, status monitoring, local annotation,
and product archiving. The cabinet also contains the narrowband links used
between the PUP and its associated RPG for internal product requests and
distribution, and for external product requests and distribution from non-associated
RPG's. The narrowband communication
links are modem-based serial data links which are directly interconnected
for internal communications, or utilize transmission over leased or dial-up
commercial telephone lines for external data distribution.
PUP Workstation. The PUP workstation is the primary
operator work area. It includes two high-resolution color-graphics monitors,
a puck-operated product selection tablet, a dedicated
color-graphics printer, and an applications
terminal for keyboard entry and CRT display of status data and alphanumeric
product data.
System Console.
The System Console is an alphanumeric display terminal which is used for
local control and testing of the PUP display processor.
RPIE Group. The RPIE comprises the equipment shelters
(Radar, Generator, and MLOS), towers (radar, guyed MLOS, and self-supporting
MLOS), Radome, and auxiliary equipment. The auxiliary equipment includes
power distribution (including backup power generation) and lighting; heating,
ventilating, and air conditioning; fire detection and suppression, and
security and status monitoring.
Leading Particulars
This section provides an overview of the various site,
equipment group, and equipment cabinet configurations; site layout and
equipment locations; and the physical characteristics of the equipment
supplied.
To support the needs of a variety of users with differing
requirements, the number of equipment groups comprising a WSR-88D system,
the siting of equipment groups, the physical arrangement of equipment,
and the functional configuration of individual equipment are variable.
The individual equipment groups (RDA, RPG, and PUPs) of an WSR-88D system
may be collocated at a single facility; however, these elements are usually
separated. The RDA's location is optimized for radar coverage requirements.
The RPG is either collocated with an RDA (radar antenna) site or located
at a principal user site. The associated PUPs (there are usually more than
one PUP associated with an RPG) are located at the various user's operational
facilities, and are usually connected to their associated RPG by dedicated
line. (There are also standalone PUPs which are not associated with any
RPG. These PUPs communicate with RPGs via dial lines.)
WSR-88D System
Familiarization
The WSR-88D is a software-driven stand alone system which
detects, processes, displays, and distributes radar weather information.
The system is primarily comprised of five (5) major groups of equipment.
These groups are:
RDA Group (Radar Data Acquisition Group)
WBC Group (Wide-Band Communications Group)
RPG Group (Radar Products Generation Group)
PUP Group (Principal User Processor Group)
RPIE Group (Real Property Installed
Equipment)
The purpose of the WSR-88D is to (through improved technology) reduce the losses associated with severe and other storms. Unlike older model weather radar systems, the WSR-88D incorporates fully automatic operation of all system data collection functions. Operator inputs at several of the WSR-88D's user terminals and/or workstations control the system data acquisition, processing, and display configurations.
The WSR-88D system is designed to support the needs of
many users. As a result, the physical configuration of each WSR-88D
might vary somewhat from that of other systems- Equipment complement, arrangement,
and software set-up may be unique to an individual site. The
discussion will generally describe any WSR-88D system. However,
it should be noted that variations will exist in nearly every system installation.
RDA Group.
The RDA is a Doppler radar subsystem which acts as the data "sensor" for the WSR-88D system. The RDA generates and radiates pulses of RF energy, then detects and processes reflected energy from radar targets. The received energy is converted from analog to digital form, then processed by the RDA into base data. Base data consists of measurements of reflectivity, mean radial velocity, and velocity spectrum width. The base data is made available for digital "archiving" and for transmission from the RDA to the RPG Equipment GROUP-
The RDA is a self-contained system within the WSR-88D configuration. As such, it is designed to operate continuously in an automatic and unattended manner.
Equipment in the RDA configuration include:
Radar
Tower Assembly
Radar Antenna/Pedestal
Radar Transmitter
Radar
Receiver
Radar
Data Processing Cabinet
The WBC communications system links the RDA group with the RPG group. In NWS installations, the WBC equipment will either consist of a hard-wired communications path or a Telco "tl" link. Some selected configurations will utilize a microwave link (MLOS) or a fiber-optic (FO) communications path. The choice of the WBC configuration will depend on several factors, including equipment complement, distances to/from RDA and RPG, local obstructions to communications, etc.
A hard-wired communications path is used when the physical distance between RDA and RPG is 400 feet or less. Fiber Optics equipment may be utilized for inter-unit distances up to 1 8 Kilometers, and microwave systems are employed when the RDA and RPG are more distant. Only a few NWS sites will employ microwave transceivers.
Generally, the WBC equipment provides high-speed intercomputer
data communications between the RDA and RPG. Base data and radar
status are sent from the RDA to the RPG, and control data is transferred
from the RPG to the RDA. The data transmission rate of the WBC equipment
is 1.544 million bits per second.
RPG Group.
The RPG equipment receives base data and status information from the RDA, and performs the appropriate processing on each. After processing, the resulting data is stored, and made available for distribution over narrowband (NB) communicates circuits to the radar systems users. Narrowband communications circuits employ either direct-connected or telephone circuits. Users may include PUPS, PUES, and other selected entities. One PUP will be designated as the primary (RPGOP) data user, but several PUP systems may be permanently connected to an RPG group. Telephone lines which are connected to the RPG may be either dial-up or dedicated circuit configurations, and may operate at more than one data transfer (bps) rate. The usual RPG telephone circuit will operate at 9600 bits per second. Data transfer is synchronous.
Base data from the RDA is processed by the RPG into base products. These products, representing REFLECTIVITY, RADIAL VELOCITY, and SPECTRUM WIDTH, are made available to users over the NB circuits. In addition, the RPG further process the base data to develop a set of derived meteorological products. These products are also sent to the appropriate user function over the narrowband communication lines.
The RPG group consists of the following equipment:
RPG Data Processing Cabinet
RPG Communications Cabinet
Unit Control Position (UCP)
The RPG Data Processing Cabinet contains the computer hardware and software required to perform real-time generation and storage of weather products. In addition the equipment hardware (and software) provides system remote control, status monitoring, error detection, product archiving, and processing for remote rain gage (hydro meteorological) data collection.
The RPG communications cabinet contains the equipment necessary to provide the narrowband communications links between the RPG and its connected PUPs and other users.
The Unit Control Position (UCP) consists of a multi-port
alphanumeric terminal and a line printer. The UCP is used by operators
and maintenance technicians for on-line data display, data entry, RPG control,
remote RDA control, system tests, and troubleshooting. Much of the
day-today activity at the UCP will involve local product selection, generation,
and distribution control. The UCP is a primary interface between
the operator and the WSR-88D operational function. Many site parameters
may be controlled at the UCP, and as a result, multiple-level password
protection is built into the interfacing RPG system software.
PUP Group.
The PUP equipment receives base and derived products from the RPG. The products are stored in the PUP database, and are made available for display. Operations personnel at the PUP may request, display, archive, and annotate weather products. In addition, the products can be made available to other users which may be directly connected (via NB circuits) to the PUP equipment. The PUP group equipment consists of a PUP Data Processor Cabinet, a PUP workstation, and a System console.
The PUP Data Processor Cabinet houses the data processing computer hardware and software necessary for graphics processing and display, local control, status monitoring, local archiving, and annotation of display products. The cabinet houses two computers. One functions as a primary processor, and the second is a graphics processor. In addition, the cabinet contains the required narrowband communications hardware for both internal and external data transfer. Just as in the RPG communications equipment, the PUP NB circuits can be comprised of dial-up and/or dedicated telephone circuits. Again, these modem-based links operate synchronously at 9600 bps- One of the PUP narrowband circuits operates without the use of telephone circuits. This line is connected directly to the RPG, and operates at 56Kbps. Instead of modems, the circuit utilizes RS232-RS422 converters.
The PUP Workstation is the primary OPERATOR work- area for the WSR-88D system. The equipment configuration includes two (2) high resolution color-graphics monitors, a "puck" operated product selection device (graphics tablet), a dedicated color graphics printer, and an applications" terminal. This terminal is used to interface with the Display Processor USER program(s).
The System Console
is an alphanumeric display device used to interface with the Display processor
SYSTEM program (operating system) and with the diagnostic software.
The System Console hardware is identical to the "applications" terminal
described in the previous paragraph. In most PUP configurations,
the two terminals will probably be located adjacent to one another (such
as they are at NWSTC). The Applications Terminal and System Terminal
are both dual-port applications-ia-numeric devices. The second port
of the Application Console is connected to the Graphics processor.
The second port of the System Console may be connected to the RPG, if the
RPG is located at the same facility as the PUP.
RIPE Group.
The RIPE (Real Property Installed Equipment) includes
the equipment shelters (RDA equipment and Generating equipment), MLOS shelter(s),
towers (Radar and MLOS), Radome, and other auxiliary equipment. RIPE
includes power distribution equipment (including standby power generation),
lighting, heating, ventilation, air conditioning, fire detection and suppression,
security, and status monitoring equipment.
