Air Traffic Management Concept Baseline Definition - The Boeing ...

network does not provide adequate spatial or temporal resolution to monitor the
atmospheric environment on this scale, and the accuracy of weather forecasts suffers as a
result. The absence of upper-air data in the oceanic domain also seriously degrades the
performance of NWP models, especially of forecasts issued for coastal areas and of aloft
conditions expected during intercontinental flight operations.
To compensate for the lack of data coverage in inland areas, networks of Doppler radars
are being used to provide supplementary upper-air observations. Three categories of
radars are currently providing upper-air information. These include the WSR-88D
(NEXRAD) Doppler weather radar, the Terminal Doppler Weather Radar (TDWR), and
Doppler radar wind profilers (RWP), which can be equipped with radio acoustic sounding
systems (RASS) for temperature profiling. When fully deployed, the NWS and DOD will
operate a nationwide network of 138 NEXRAD radars, and the FAA will operate TDWRs
in 34 terminal areas. Both of these radar systems measure near-surface winds in storm
environments, and provide vertical profiles of winds in the clear air during periods when
hazardous weather conditions are not occurring.
The only operational RWP network providing upper-air data for aviation analysis and
forecasting applications is the Wind Profiler Demonstration Network (WPDN) operated
by NOAA’s Forecast Systems Laboratory (FSL). This network of 404-MHz radars
provides continuous measurements of upper-air winds through much of the troposphere.
There are 32 profilers in the WPDN, most located in the midwest. The WPDN has been
operational for almost a decade, but has been threatened with elimination because the
radar frequency interferes with search and rescue satellite operations. Plans are being
considered to convert the WPDN to 449 MHz and to expand the network into the
Caribbean and Alaska. In the near term, maintaining and expanding the WPDN would
likely benefit aviation weather information by providing enhanced spatial and temporal
resolution of aloft winds. For example, RWP data in the TRACON area could improve
the quality of aircraft trajectories calculated by the CTAS system. In addition, there are
now some semi-permanent networks of so-called ‘boundary layer’ RWP and RASS that
operate near 1 GHz and provide continuous observations of winds and temperatures in the
first 1-3 km of the atmosphere. The usefulness of data from these instruments in aviation
weather applications has not yet been explored to any degree. In the near term, the impact
of RWP data from boundary layer profilers on CNS/ATM technologies like CTAS should
be investigated.
The quality of Doppler radar wind data has been the subject of several studies in recent
years. There is no way to determine the absolute accuracy of these instruments, since the
data can not be compared to absolutely known values or reference standards in the same
way that surface sensors can be checked. Based on recent intercomparison studies, the
accuracy of Doppler radar wind data is on the order of ±1.0 m/s on a vector component
basis, with rms errors of about 2.0-2.5 m/s. The completeness of Doppler radar wind data
depends on atmospheric conditions. Higher temperatures and humidities generally
produce good data recovery, while cold, dry conditions limit data availability. All three
Doppler radar system also suffer from contamination from biological targets, especially
migrating birds (Wilzak et al., 1994). Migrating birds often appear in Doppler radar data
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