Geoscience Reference
In-Depth Information
Fig. 5
Global mass change
of the atmosphere derived
from
C
00
basedonECMWF
operational analysis (1980-
2009) pressure level data
reduced to surface topography
Fig. 6
Degree 1 TL-coefficients derived from ECMWF operational analysis (1980-2009) pressure
level data reduced to surface topography, in black
C
10
,inblue
C
11
and in red
S
11
pressure from the ECMWF operational analysis and re-analysis data over 30 years,
where the most prominent signal is the yearly variation, which is primarily due to
changes in the hydrological cycle adding water vapor to the air, particularily in the
Northern Hemisphere summer.
The degree 0 coefficient of the atmospheric potential field is directly linked to
the total mass of the atmosphere. Figure
5
shows the time series of the mass change
derived from the
C
00
atmospheric gravity coefficient of the years 1980 until 2009.
The yearly signal is clearly visible. Also a notable trend becomes evident which
suggests an increase of the atmospheric mass of 3
10
13
kg/year. Considering
that atmospheric mass changes are caused mainly through variation of its wet part, it
is an indication that the atmosphere has become warmer and thus more humid within
this period.
Figure
6
shows a time series of the degree 1 coefficients
C
10
,
C
11
and
S
11
which
are closely tied to the center of mass (see Eq. (
28
)). In contrast to the mass, in this
.
26
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