Geoscience Reference
In-Depth Information
1020
1000
980
ECMWF
local
GPT
Berg
960
940
2008
2009
2010
Fig. 5
Pressure values for station O'Higgins in Antarctica from the ECMWF (
grey line
), local
pressure recordings at the radio telescope (
red squares
), GPT (
blue line
), and pressure determined
with the model by Berg (
1948
)(
black bold line
)
0˚
0˚
−90˚
−90˚
90˚
90˚
−180˚
−180˚
180˚
180˚
5
45˚
45˚
45˚
45˚
4
3
0˚
0˚
0˚
0˚
2
−45˚
−45˚
−45˚
−45˚
1
−180˚
−180˚
180˚
180˚
−90˚
−90˚
90˚
90˚
0˚
0˚
Fig. 6
Simulated station height standard deviations in mm for GPT with respect to the pressure
values provided by the ECMWF (based on 36 epochs in 2005 for a 2
◦
latitude times 2.5
◦
longitude
grid) (modified from Böhm et al. (
2009b
))
station height errors of more than 10 mm. The errors for GPT for this region are
smaller, and these might completely disappear with an increased degree and order
of the spherical harmonic expansion. There are almost no biases for the rest of the
Earth (see Böhm et al. (
2009b
)).
GPT only accounts for an annual variation of the pressure with rather small ampli-
tudes compared to the other (e.g. weekly) variations of the pressure. Thus, the stan-
dard deviations of the differences to the grid values from the ECMWF are almost the
same for the Berg model (constant pressure per site) and GPT. In Fig.
6
the simulated
station height standard deviations are plotted for the case of using GPT compared
pressure values from the ECMWF. There is an increase of the standard deviations
