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