Geoscience Reference
In-Depth Information
Ta b l e 4
Increments for
ray-tracing following Rocken
et al. (
2001
)
between (km)
0-2
2-6
6-16
16-36
36-136
increment (m)
10
20
50
100
500
Fig. 4
Temperature versus
height of the meteorological
values provided with pressure
level data (
red crosses
)and
from inter- and extrapolation
(
black line
)
140
120
100
80
60
40
interpolated
pressure level data
20
0
200
300
400
500
600
700
Temperature [K]
applied. If the station height is at sea level, approximately 1000 layers are to be
deployed (Table
4
).
Temperature can be interpolated linearly but it should be extrapolated according
to a standard model for the temperature (Table
3
). An example is shown in Fig.
4
.
The water vapor pressure
e
can be interpolated with an exponential approach
e
(
h
−
h
0
)/
c
=
e
0
·
e
(37)
where
e
0
and
h
0
denote the water vapor pressure and the height of the lower-next
level where
e
is provided. The coefficient
c
can be determined from the water vapor
pressure at two adjacent levels (compare Fig.
5
). Other authors like Hobiger et al.
(
2008
) use linear interpolation of relative humidity. The total pressure
p
can be
determined with the hypsometric equation
R
d
·
T
v
p
0
p
−
h
0
=
h
(38)
g
which is based on Eq.
25
and where the index 0 refers to the closest level where
meteorological data are available, and the virtual temperature
T
v
and gravity
g
are
determined at the mean height
(
h
+
h
0
)/
2 (see Fig.
6
).
