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NEXt Generation Weather RADar

Project Description
The NEXRAD system (also known as Weather Surveillance Radar -
1988 Doppler) is oneof NOAA's prime observation systems for
acquiring information about meteorologicalconditions, and is
also one of the key systems in NOAA's modernization and
restructuring. Byusing Doppler radar technology, forecasters
can observe the presence of precursor conditions ofsevere
weather such as tornadoes, large hail and damaging thunderstorm
winds. NEXRADallows for the detection of wind circulation
patterns (e.g., mesocyclones) as precursors totornadic activity
and provides data on the direction and speed of tornado cells
once they form. NEXRAD also provides quantitative estimates of
precipitation, which are important inforecasting flash floods,
main stream river flooding and in water resource
management. Thesevere weather and storm wind field detection
capabilities offered by NEXRAD have contributedto a significant
increase in the accuracy and timeliness of NWS warnings. The
advantages ofNEXRAD ov! er conventional radars can be broken
down into five basic areas: improvedsensitivity, improved
resolutions, wind velocity estimation, automated data
collection in threedimensions, and capability for scientific
processing of data. The benefits of this system will continue
to be improved through scientific advances inthe use of weather
radar data, and through improved processing and data
disseminationcapabilities. A NEXRAD Product Improvement (NPI)
Program has been established to plan andimplement these
continued improvements. The primary goal of the NPI Program is
to modify,augment and improve upon the existing capabilities of
the NEXRAD system so it can support, ina cost-effective and
timely manner, known operational requirements, as well as
thoserequirements that can reasonably be anticipated.The NWS is
currently implementing two major upgrades to the NEXRAD system:
theOpen Systems Radar Product Generator (ORPG) and the Open
Systems Radar Data Acquisition(ORDA). ORPG will ! be deployed
in the calendar year 2000-2002 time frame. ORDA isschedule d
for deployment in the 2002-2004 time frame. The deployment of
ORPG will enablethe NWS to implement many additional scientific
products and to support better communicationscapabilities,
including dissemination of base data as required. ORDA
deployment will enableimprovements in data quality, including
mitigation of range folding, also known as 'purple haze.' Work
is also underway to develop and test a dual polarization
capability for NEXRAD. Dual polarization is a radar signal
transmission, reception and processing scheme that
providesinformation on the relative height and width of
precipitation targets. Significant improvementsare anticipated
in estimating the amount of rainfall and identifying
precipitation types such asrain, snow and hail. If the
development and testing validate the promise.

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