EVALUATION OF GPS DROPWINDSONDES
Principal Investigator:
James L. Franklin
Collaborating scientist(s):
Steven E. Feuer
Objective:
To evaluate and process data from the new NCAR GPS dropwindsonde.
Background:
The GPS dropwindsonde was developed by NCAR to serve as the primary scientific
instrumentation of the new Gulfstream IV (G-IV) jet aircraft, which will begin
operational flights in the environments of potential landfalling hurricanes in
1997. HRD has been assigned responsibility for providing real-time
quality-control of the dropwindsonde data on the G-IV. In addition, GPS
dropwindsonde systems have been installed on the two WP-3D aircraft, where they
replace the previous generation of Omega dropwindsondes (ODWs).
Accomplishments:
A total of 88 GPS dropsondes were released from the G-IV and one of the P-3s
during the summer and fall of 1996. In addition, 737 soundings from the FASTEX
project, and 31 from the ADEOS project were available for study. These sondes
were examined for reliability and accuracy. Failure rates and typical
measurement accuracies were determined (TABLE 1). Except for the
performance of the dual-heated H humicap, reliability and accuracy of the sonde
were excellent. GPS wind accuracies were occasionally disappointing, but were
almost always better than those obtainable from the ODW.
Software developed for real-time processing on the G-IV was enhanced to
accomodate post-flight processing (quality-control) as well. Postscript
versions of general sonde plotting, skew-t diagrams, and synoptic data
plotting software were developed. All sonde data from the 1996 Field Program,
including sondes from the G-IV test flights, were processed. Data from the
ADEOS project were also processed.
Plans:
GPS dropwindsonde data obtained from the 1997 Hurricane Season (from both the
P-3s and the G-IV) will be examined for reliability and accuracy. Processed
data sets will be prepared. Of particular interest will be the performance of
the humidity sensors, and the determination of an optimal heating profile.
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Last modified: 23 June 1997.
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