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

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

Universal System 1930s Optical Theodolite Photo courtesy of NOAA Archive

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

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

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

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

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

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

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

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

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

RDF Winds as Function of Height

GPS Winds as Function of Height

GPS vs. RDF Winds

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

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

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?

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