Assessment of Nexrad Coverage and Associated Weather Services (1995) / Chapter Skim
Currently Skimming:
A Criteria for Evaluation of a Weather Radar System
A Criteria for Evaluation of a Weather Radar System
Pages 65-86
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From page 65... ...
RADAR TECHNICAL ASPECTS This section provides a system description and radar performance specifications and discusses the key radar technical aspects that were considered in developing criteria for addressing the quality of radar coverage. Key radar technical aspects include coverage at specific altitudes, spatial and temporal resolution, sensitivity, Doppler coverage, and radar availability.
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From page 66... ...
Radar coverage with limited Doppler capability was available in the preNEXRAD NWS network only at Montgomery, Alabama; Marseilles, Illinois; and Huntsville, Alabama. Therefore, for weather phenomena that can only be detected using Doppler features (e.g., mesocyclones or microbursts)
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From page 67... ...
o ~ 'e ti; - o o co o Q o L o, CD C' a, ~ 0 'G)
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From page 68... ...
the interfering effects of ground clutter are at a maximum." The NEXRAD clutter suppression feature mitigates this limitation to a considerable extent. At long ranges both the Earth's curvature and the increasing resolution cell size reduce the radar's ability to detect weather phenomena.
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From page 69... ...
on NEXRAD cross-beam resolution and coverage of low-level weather phenomena. Courtesy of SRI International.
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From page 70... ...
At close ranges the resolution is governed by the pulse length, and at long ranges it is governed by the antenna beam width. The narrower beam of the NEXRAD antenna gives it an advantage over earlier National Weather Service (NWS)
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From page 73... ...
from NEXRAD operators experienced win the old radars, He pane! concludes that the type and amount of information from NEXRAD's set scan strategy, especially use of the four-panel storm and velocity structure display, is as effective as a vertical scan and has contributed to the improved probability of detection for severe storms.
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From page 74... ...
The pre-NEXRAD network has this capability over only 30 percent of the area. For most purposes radar sensitivity does not limit the operational performance of the NEXRAD, but its greater sensitivity allows detection of a greater percentage of weak weather phenomena than the pre-NEXRAD radars could observe.
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From page 75... ...
Courtesy of SRI International. ~ I Figure A-Sb Areas of the contiguous United States and border regions having better resolution coverage at 10,000 ft above site level with NEXRAD (red)
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From page 77... ...
Figure A-7 Radar sensitivity curves showing reflectivity factor (dBZ) versus range for the single-pulse radar return power that yields equal signal and noise power, SNR = 1.
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From page 78... ...
The possible impact of limited DoD NEXRAD availability has been addressed in this study by considering both the full NEXRAD network and a degraded network that includes only NWS NEXRADs when assessing the ability to detect certain weather phenomena.
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From page 79... ...
~J 0 dB i crelnents' an e in I acentric he colors cb g nnerrnost co -, e at lO,OOO it ab°Ve slitiVitY hick is silo n as red ( t'~ ooo ft above site levetbat the c R D VersUs ~3xicates equal se~siti~tyi ~n
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From page 82... ...
The NEXRAD Doppler signal processor uses modern digital signal processing to compute accurate estimates of radar reflectivity and velocity while simultaneously suppressing interference and artifacts in He data, such as ground clutter. The WSR-57s and WSR-74s had no clutter-cancellation capability.
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From page 83... ...
They include the following: signal processing that provides digital or analog radar data from which weather products can be displayed or derived; algorithms that translate radar data into weather information- for example, radar reflectivity translated into rainfall rate and cumulative rainfall over some period of time, or reflectivity and velocity data combined in a hail detection and had! severity product; products that present this information in graphical image or alphanumeric format (Klazura and Imy, 1993~; displays, which provide presentations of radar data and derived products; and · data archiving (recording)
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From page 84... ...
Furthermore, the four private NEXRAD information dissemination service data providers create national mosaics of NEXRAD products (Beer, 1991~. These mosaics, because of their increased quantitative products, are superior to those provided through the pre-NEXRAD network.
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From page 85... ...
The technical features of the NEXRAD allow the development and provision of new products and services that were, heretofore, unavailable. Many of the new NEXRAD products are available to users from the NEXRAD information dissemination service providers.
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