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Atmospheric pressure loading effects on Global Positioning System coordinate determinationsEarth deformation signals caused by atmospheric pressure loading are detected in vertical position estimates at Global Positioning System (GPS) stations. Surface displacements due to changes in atmospheric pressure account for up to 24% of the total variance in the GPS height estimates. The detected loading signals are larger at higher latitudes where pressure variations are greatest; the largest effect is observed at Fairbanks, Alaska (latitude 65 deg), with a signal root mean square (RMS) of 5 mm. Out of 19 continuously operating GPS sites (with a mean of 281 daily solutions per site), 18 show a positive correlation between the GPS vertical estimates and the modeled loading displacements. Accounting for loading reduces the variance of the vertical station positions on 12 of the 19 sites investigated. Removing the modeled pressure loading from GPS determinations of baseline length for baselines longer than 6000 km reduces the variance on 73 of the 117 baselines investigated. The slight increase in variance for some of the sites and baselines is consistent with expected statistical fluctuations. The results from most stations are consistent with approximately 65% of the modeled pressure load being found in the GPS vertical position measurements. Removing an annual signal from both the measured heights and the modeled load time series leaves this value unchanged. The source of the remaining discrepancy between the modeled and observed loading signal may be the result of (1) anisotropic effects in the Earth's loading response, (2) errors in GPS estimates of tropospheric delay, (3) errors in the surface pressure data, or (4) annual signals in the time series of loading and station heights. In addition, we find that using site dependent coefficients, determined by fitting local pressure to the modeled radial displacements, reduces the variance of the measured station heights as well as or better than using the global convolution sum.
Document ID
19950048340
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Vandam, Tonie M.
(NOAA, Silver Spring, MD United States)
Blewitt, Geoffrey
(University of Newcastle upon Tyne Newcastle upon Tyne, United Kingdom)
Heflin, Michael B.
(Jet Propulsion Laboratory, Pasadena, CA United States)
Date Acquired
August 16, 2013
Publication Date
December 10, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: B12
ISSN: 0148-0227
Subject Category
Geosciences (General)
Accession Number
95A79939
Funding Number(s)
CONTRACT_GRANT: NAS5-32331
Distribution Limits
Public
Copyright
Other

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