TY  - JOUR
N1  - Copyright 2008 by the American Geophysical Union.
ID  - epprod6993
UR  - http://dx.doi.org/10.1029/2007GL032252
IS  - L03302
A1  - King, MA
A1  - Watson, CS
A1  - Penna, NT
A1  - Clarke, PJ
Y1  - 2008///
N2  - Estimates of seasonal geophysical loading from GPS
may be biased by propagated unmodeled subdaily signals.
Although the major geophysical signals at semidiurnal and
diurnal frequencies are now routinely modeled in GPS
analyses, the characteristics of unmodeled or mismodeled
subdaily signals are not well known. Here, using site
coordinates estimated every 5 minutes, we examine the
subdaily coordinate spectral characteristics for ~90 global
GPS sites. Unmodeled signals with amplitudes at the 10 mm
level are present at frequencies between ~1/day and the
Nyquist frequency. These are shown to propagate into 24 h
solutions with (among other frequencies) annual and
semiannual periods with amplitudes up to 5 mm, with a
median amplitude in the height component of 0.8 mm
(annual) and 0.6 mm (semiannual). They are shown to bias
low-degree spherical harmonics estimates of geophysical
loading at the level of 5?10%, although the exact effect will be network dependent.
JF  - Geophysical Research Letters
VL  - 35
KW  - GPS; sub-daily signals; geophysical loading
SN  - 0094-8276
TI  - Subdaily signals in GPS observations and their effect at semiannual and annual periods
SP  - 1
AV  - restricted
EP  - 5
ER  -