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| Titel |
A simulation study with a new residual ionospheric error model for GPS radio occultation climatologies |
| VerfasserIn |
J. Danzer, S. B. Healy, I. D. Culverwell |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 8 ; Nr. 8, no. 8 (2015-08-21), S.3395-3404 |
| Datensatznummer |
250116537
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| Publikation (Nr.) |
 copernicus.org/amt-8-3395-2015.pdf |
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| Zusammenfassung |
In this study, a new model was explored which corrects for higher
order ionospheric residuals in Global Positioning System (GPS) radio
occultation (RO) data. Recently, the theoretical basis of this new
"residual ionospheric error model" has been outlined
(Healy and Culverwell, 2015). The method was tested in simulations with
a one-dimensional model ionosphere.
The proposed new model for computing the residual ionospheric error is
the product of two factors, one of which expresses its variation from
profile to profile and from time to time in terms of measurable
quantities (the L1 and L2 bending angles), while the other
describes the weak variation with altitude. A simple integral
expression for the residual error (Vorob’ev and Krasil’nikova, 1994) has
been shown to be in excellent numerical agreement with the exact
value, for a simple Chapman layer ionosphere. In this case, the
"altitudinal" element of the residual error varies (decreases) by no
more than about 25 % between ~10 and ~100 km for physically reasonable Chapman layer
parameters. For other simple model ionospheres the integral can be
evaluated exactly, and results are in reasonable agreement with those
of an equivalent Chapman layer.
In this follow-up study the overall objective was to explore the
validity of the new residual ionospheric error model for more detailed
simulations, based on modeling through a complex three-dimensional
ionosphere.
The simulation study was set up, simulating day and night GPS RO
profiles for the period of a solar cycle with and without an
ionosphere. The residual ionospheric error was studied, the new error
model was tested, and temporal and spatial variations of the model
were investigated. The model performed well in the simulation study,
capturing the temporal variability of the ionospheric
residual. Although it was not possible, due to high noise of the
simulated bending-angle profiles at mid- to high latitudes, to perform
a thorough latitudinal investigation of the performance of the model,
first positive and encouraging results were found at low
latitudes. Furthermore, first application tests of the model on the
data showed a reduction in temperature level of the ionospheric
residual at 40 km from about −2.2 to
−0.2 K. |
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