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Proceedings Paper

Generating climate benchmark atmospheric soundings using GPS occultation data
Author(s): Anthony J. Mannucci; Chi O. Ao; Thomas P. Yunck; Larry E. Young; George A. Hajj; Byron A. Iijima; Da Kuang; Thomas K. Meehan; Stephen S. Leroy
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Paper Abstract

Atmospheric soundings derived from Global Positioning System radio occultations (GPSRO) acquired in low-Earth orbit have the potential to be global climate benchmark observations of significant value to the Global Climate Observing System (GCOS). Geophysical observables such as atmospheric pressure and temperature are derived by measuring propagation delay induced by the atmosphere, a measurement whose fundamental unit-the second-is absolutely determined by calibration against atomic clocks. In this paper, we analyze the sources of systematic and random error for GPSRO soundings to determine the steps needed to establish GPSRO as a climate benchmark observation. Benchmarks require specific processing strategies and specific forms of documentation so that confidence in the accuracy and precision of the measurements is assured. Establishing calibration traceability to absolute standards (SI-traceability) is an essential strategy. We discuss a wide range of error sources in a geophysical retrieval, such as orbit determination error, signal delay in the Earth's ionosphere, and quality control strategies. Uncalibrated ionospheric delay is identified as the error source deserving the most attention in establishing SI-traceability of the retrievals, to meet stringent climate observation requirements of 0.5 K accuracy and 0.04 K stability. Profile comparisons from the recently launched COSMIC constellation establish strong upper limits on systematic error arising from the individual instruments. These encouraging results suggest that GPSRO should become a permanent resource for the GCOS. These highly precise and accurate instruments can be deployed on future Earth Observation satellites at a low per-sensor cost and minimal interference to existing and planned observational programs.

Paper Details

Date Published: 1 September 2006
PDF: 14 pages
Proc. SPIE 6301, Atmospheric and Environmental Remote Sensing Data Processing and Utilization II: Perspective on Calibration/Validation Initiatives and Strategies, 630108 (1 September 2006); doi: 10.1117/12.683973
Show Author Affiliations
Anthony J. Mannucci, Jet Propulsion Lab. (United States)
Chi O. Ao, Jet Propulsion Lab. (United States)
Thomas P. Yunck, Jet Propulsion Lab. (United States)
Larry E. Young, Jet Propulsion Lab. (United States)
George A. Hajj, Jet Propulsion Lab. (United States)
Byron A. Iijima, Jet Propulsion Lab. (United States)
Da Kuang, Jet Propulsion Lab. (United States)
Thomas K. Meehan, Jet Propulsion Lab. (United States)
Stephen S. Leroy, Harvard Univ. (United States)


Published in SPIE Proceedings Vol. 6301:
Atmospheric and Environmental Remote Sensing Data Processing and Utilization II: Perspective on Calibration/Validation Initiatives and Strategies
Allen H. L. Huang; Hal J. Bloom, Editor(s)

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