1. 2 (14) Universal Upper Air Sounding System
World Meteorological Organization WMO Technical Conference on Meteorological and Evironmental Instruments and Methods of Observation – TECO 2005

2. What is a Universal Upper Air System?
Flies sondes from any qualified manufacturer
Operates in multiple modes (RDF/GPS)
Complies with WMO and national reporting requirements
Photo courtesy of NOAA Archive

3. Universal System 1930s Optical Theodolite
Photo courtesy of NOAA Archive

4. Universal System 1940s SCR-658 Manual Radiotheodolite
Photo courtesy of NOAA Archive

5. ART-1 and ART-2 Automatic Radiotheodolites
Universal System: 1950s
ART-1 and ART-2 Automatic Radiotheodolites
Photos courtesy of NOAA Archive

6. 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

7. In 2000 the Radiotheodolite returns as part of the NWS Radiosonde Replacement System
Photo: InterMet Systems

8. 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

9. 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

10. 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

11. Operational factors favor 403 MHz 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

12. 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

13. RDF Winds as Function of Height

14. GPS Winds as Function of Height

15. GPS vs. RDF Winds

16. Cost factors favor Universal RDF:
Low cost disposable
Multiple vendors for sonde reorders
Estimated Savings from Universal RDF System:

17. Universal Compatibility:
The Signal Processor (decoder) is the key to multi-sonde use
Other Issues:
Bandwidth
Frequency selection
Transfer of calibration coefficients
Solar correction
Signal Processor

18. 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?

19. 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