Atmospheric Chemistry and Physics Discussions
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2007
10.5194/acpd-7-3179-2007
http://www.atmos-chem-phys-discuss.net/7/3179/2007/
http://www.atmos-chem-phys-discuss.net/7/3179/2007/acpd-7-3179-2007.html
http://www.atmos-chem-phys-discuss.net/7/3179/2007/acpd-7-3179-2007.pdf
3179
3202
2007-02-27
Azimuthal asymmetry in ground-based GPS slant delay observations and their NWP model counterparts
R. Eresmaa
reima.eresmaa@fmi.fi
H. Järvinen
S. Niemelä
K. Salonen
Finnish Meteorological Institute, Erik Palménin aukio 1, 00100 Helsinki, Finland
The ground-based measurements of the Global Positioning System (GPS)
allow estimation of the tropospheric delay along the slanted signal
paths through the atmosphere. The meteorological exploitation of such
slant delay (SD) observations relies on the hypothesis of azimuthal
asymmetry of the information content. This article addresses the
validity of the hypothesis.
<br><br>
The asymmetric properties of the SD observations and their model
counterparts are investigated. In this study, the model counterparts
are based on 3-h forecasts of a numerical weather prediction (NWP)
model, run with four different horizontal resolutions. The SD
observations are compared with their model counterparts with emphasis
on cases of high asymmetry in order to see whether the observed
asymmetry is a real atmospheric signature.
<br><br>
The asymmetric delay component is found to be of the order of a few
parts per thousand of the absolute SD value, thus barely exceeding the
assumed standard deviation of the SD observation error. However, the
observed asymmetric delay components show a statistically significant
meteorological signal. Benefit of the asymmetric SD observations is
therefore expected to be taken in future, when NWP systems will
explicitly represent the small-scale atmospheric features revealed by
the SD observations.
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