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@BOOK{Kunz:136185,
author = {Kunz, Anne},
title = {{O}bservation- and model-based study of the extratropical
{UT}/{LS}},
volume = {54},
school = {Universität Wuppertal},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {PreJuSER-136185},
isbn = {978-3-89336-603-3},
series = {Schriften des Forschungszentrums Jülich. Reihe Energie und
Umwelt / Energy und Environment},
pages = {XII, 120, XII S.},
year = {2010},
note = {Record converted from JUWEL: 18.07.2013; Univ. Wuppertal,
Diss., 2009},
abstract = {Coupling between processes of different nature, as
radiation, dynamics and chemistry, in the upper troposphere
and lower stratosphere (UT/LS) makes this region highly
sensitive to climate change. This thesis addresses the
climatological representativeness of trace gases measured
in–situ within the UT/LS as well as their temporal
variability. Possible atmospheric processes which may
contribute to the maintenance of tropopause related
structures in the extratropics are discussed. These studies
are based on the closely linked use of experimental data,
statistical analyzes and atmospheric models. In the first
part of this thesis, a statistical analysis is presented for
the comparability of water vapor (H$_{2}$O) and ozone
(O$_{3}$) data sets sampled during the SPURT aircraft
campaigns and the MOZAIC passenger aircraft flights. A
different variability character in both trace gas data sets
is evident by a variance analysis. While the SPURT H$_{2}$O
data can only resolve atmospheric processes variable on a
diurnal or synoptic time scale, MOZAIC H$_{2}$O data also
resolve processes on an inter–seasonal and a seasonal time
scale. The SPURT H$_{2}$O data set does not represent the
full MOZAIC H$_{2}$O variance in the UT/LS for
climatological investigations, whereas the variance of
O$_{3}$ is much better represented. SPURT H$_{2}$O data are
better suited in the stratosphere, where the MOZAIC relative
humidity sensor loses its sensitivity. This is the first
analysis which addresses the ability of measured trace gases
to detect the atmospheric variability in the UT/LS. In the
second part of the thesis, the relationship between the
static stability N$^{2}$ within the tropopause inversion
layer (TIL) in the extratropics and the atmospheric mixing
in that region is investigated using the SPURT O$_{3}$ and
CO observations. For this purpose N$^{2}$ is determined from
ECMWF fields. A new measure of mixing degree based on
O$_{3}$–CO tracer correlations is developed. It is found
that high N$^{2}$ is related to an enhanced mixing degree in
the extratropical mixing layer. A temporal variance analysis
of N$^{2}$ at the particular SPURT measurement locations
suggests that the processes responsible for the composition
of the TIL occur on a seasonal time scale. The Reading
radiative transfer model is used to simulate the influence
of a change in O$_{3}$ and H$_{2}$O vertical gradients on
the temperature gradient and thus on the static stability
above the tropopause. Zonal and time mean ECMWF O$_{3}$ and
H$_{2}$O profiles, which are used as reference mixed
profiles, are perturbed to represent idealized non–mixed
profiles in the atmosphere. The results of the simulations
show that N$^{2}$ increases with enhanced mixing degree near
the tropopause and a temperature inversion develops. In the
idealized case of non–mixed profiles the TIL vanishes.
H$_{2}$O plays the dominant role in maintaining the
temperature inversion and the TIL structure compared to
O$_{3}$. Here, the two different atmospheric features, i.e.,
the mixing layer and the TIL in the extratropics, are
discussed together for the first time. In the last part of
the thesis, the gradient of the potential vorticity with
equivalent latitude is used to determine the core of the jet
streams and its meridional boundaries on different middle
world isentropes (300–380 K). The jet cores represent a
physical boundary on the isentropes between the troposphere
at lower latitudes and the stratosphere at higher latitudes.
Thus, a PV gradient tropopause related to the isentropic
gradient of the potential vorticity is proposed, which may
represent the separation between the two atmospheric
reservoirs troposphere and stratosphere in a more
appropriate manner than the use of a particular value of PV.
Dependent on season the zonal and time mean PV at this newly
defined tropopause varies between 2.0 PVU–3.5 PVU and
decreases from lower toward higher latitudes in the northern
hemisphere. This decrease is sharper on the southern
hemispheres compared to the northern hemisphere. The
analysis indicates that as the dynamical tropopause the
commonly used 2 PVU threshold is too low most of the time.
With the help of tracer correlations and a new coordinate
system, using equivalent latitude relative to the jet core,
the isentropic distribution and transition of the static
stability across the PV gradient tropopause is analyzed.
This transition is more pronounced during winter than summer
on each isentrope in the lowermost stratosphere, which is
consistent with the transport barrier at the jet streams
related to the sharpness of the tropopause.},
cin = {ICG-1},
ddc = {500},
cid = {I:(DE-Juel1)VDB790},
shelfmark = {UMV - Climatic change / UMV - Klimatische Auswirkungen /
FZJ - Schriftenreihen des Forschungszentrums Jülich},
typ = {PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/136185},
}
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