2 (14) Universal Upper Air Sounding System
World Meteorological Organization WMO Technical Conference on Meteorological and Evironmental Instruments and Methods of Observation – TECO 2005
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What is a Universal Upper Air System?
1. Flies sondes from any qualified manufacturer
2. Operates in multiple modes (RDF/GPS)
3. Complies with WMO and national reporting requirements
Photo courtesy of NOAA Archive
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Universal System
1930s
Photo courtesy of NOAA Archive
Optical Theodolite
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Universal System1940s
Photo courtesy of NOAA Archive
SCR-658 Manual Radiotheodolite
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ART-1 and ART-2 Automatic RadiotheodolitesPhotos courtesy of NOAA Archive
Universal System: 1950s
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1990: GPS Revolution• Rapidly dominates
synoptic market by offering high accuracy and ease of use
• High cost of disposables becomes unsustainable for many operators - leading to darkened sites
Image courtesy of USAF Research Lab
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• In 2000 the Radiotheodolite returns as part of the NWS Radiosonde Replacement System
Photo: InterMet Systems
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TRS: Telemetry Receiving System
• Multi-Sonde Compatible • Dual-Mode (GPS / RDF)• Digital Architecture• All Environment• High Gain / Long Range• Easy to Operate
Photo: InterMet Systems
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2002: iMet-1500
• TRS technology in a flexible format
• Digital receiver with tunable bandwidth
• Multi-sonde compatible
• Multi-mode GPS/RDF• Military or Synoptic
Photo: InterMet Systems
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2004: iMet-1700 • TRS technology at a
lower cost• Fixed site installations • Fewer moving parts,
reduced maintenance • Multi-sonde
compatible• Multi-mode GPS/RDF
Photo: InterMet Systems
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Operational factors favor 403 MHz GPS: GPS
• Maintenance free• Accurate winds in all
conditions• Release and forget
operations
RDF• Complex hardware• Inaccurate winds at
low elevation angles• Training and
experience required
When properly integrated, PTU is a function of the radiosonde, and should be independent of the wind finding methodology
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Tanzania Evaluation
• In October 2004, a team lead by Dr. John Nash from the Met Office evaluated an iMet-1500 installation on behalf of the WMO.– More training was required for a staff that had
not conducted synoptic flights for 10 years– Identified important integration issues– RDF Wind accuracy was deemed acceptable for
operational use in the Tropics
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RDF Winds as Function of Height
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GPS Winds as Function of Height
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GPS vs. RDF Winds
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Cost factors favor Universal RDF:• Low cost disposable• Multiple vendors for sonde reorders
Activity Level Total $ Per Flight % Diff 10 yr Life
365 flights peryear
$ 19,300 $ 53 30% $ 193,000
730 flights peryear
$ 44,850 $ 62 37% $ 448,000
Estimated Savings from Universal RDF System:
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Universal Compatibility:• The Signal Processor
(decoder) is the key to multi-sonde use
Signal Processor
• Other Issues:– Bandwidth– Frequency selection– Transfer of calibration
coefficients– Solar correction
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Meteorological Issues:
• Are RDF winds accurate enough for tropical locations with a low incidence of low angle tracking?
• Is a competitive market for annual sonde reorders compatible with providing consistent PTU time series data?
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Conclusions:
• There is a place for Universal RDF Systems in the GUAN
• Additional work needs to be done on data quality and the potential impact of annual sonde changes
Photo courtesy of NOAA Archive
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