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@PHDTHESIS{Knist:858408,
author = {Knist, Sebastian},
title = {{L}and-atmosphere interactions in multiscale regional
climate change simulations over {E}urope},
volume = {86},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
type = {Dissertation},
address = {Bonn},
publisher = {Meteorologisches Institut der Universität Bonn},
reportid = {FZJ-2018-07294},
series = {Bonner Meteorologische Abhandlungen},
pages = {viii, 147 p.},
year = {2018},
note = {Dissertation, Rheinische Friedrich-Wilhelms-Universität
Bonn, 2018},
abstract = {Interactions between the heterogenous land surface and the
atmosphere play a fundamental role in the weather and
climate system through their influence on the energy and
water cycles. Global climate models (GCMs) currently have
coarse horizontal grid resolutions in the order of 100 km.
With their higher resolution regional climate models (RCMs)
better resolve mesoscale processes in the atmosphere and
better represent the heterogenous land surface properties.
Thus, RCMs are able to provide more detailed characteristics
of regional to local climate. This thesis conducts regional
climate simulations in multiple resolutions for the European
domain of the Coordinated Regional Climate Downscaling
Experiment (EURO-CORDEX) and a central European domain
(3kmME) with the RCM WRF downscaling both ERA-Interim
reanalysis and GCM MPI-ESM-LR (RCP4.5) climate change
scenario data. The analysis focusses on land-atmosphere
interactions to gain a better understanding of the regional
water cycle components, the involved multi-scale processes,
their sensitivities and variabilities both under present-day
climate and future climate change conditions. Furthermore,
the added value of the convection-permitting 3kmME
simulations, being one of the first sets of decade-long
convection-permitting regional climate simulations over
Central Europe, is investigated. A comparison of summertime
land-atmosphere coupling strength is carried out for a
subset of the ERA-Interim-driven EURO-CORDEX model ensemble
(1989 to 2008). The coupling strength is quantified by the
correlation between the surface sensible and the latent heat
flux, and by the correlation between the latent heat flux
and 2m temperature and compared to European FLUXNET
observations and gridded observational Global Land
Evaporation Amsterdam Model (GLEAM) data, respectively. The
RCM simulations agree with both observational datasets in
the large-scale pattern characterized by strong coupling in
southern Europe and weak coupling in northern Europe.
However, in the transition zone from strong to weak coupling
covering large parts of central Europe the majority of the
RCMs tend to overestimate the coupling strength in
comparison to both observations. The RCM ensemble spread is
caused by the different land surface models applied, and by
the model-specific weather conditions resulting from
different atmospheric parameterizations. Investigation of
land-atmosphere coupling strength in ERA-Interim driven WRF
simulations in both 3 km and 12 km resolution for central
Europe reveals large year-to-year variability related to the
individual soil moisture conditions. Coupling strength
largely differs for individual land use types. Forest
compared to crop type reacts slower to drought conditions.
Coupling is overall slightly stronger in the 3 km
simulation, attributed to overall drier soils due to less
precipitation. The projected climate change based on a WRF
0.44° simulation downscaling GCM MPI-ESM-LR (RCP4.5) data
alters the European land-atmosphere coupling regimes in
summer. Due to increasingly drier soils, stronger coupling
is simulated for large parts of western, central and
southern eastern Europe for the period 2071-2100 compared to
1971-2000. Areas of strongest future increase of extreme
temperature coincide with strong coupling areas. In order to
analyse the added value of convection-permitting 3 km
climate simulations, nine years of ERA-Interim driven
simulations with the WRF RCM at 12 km and 3 km grid
resolution over central Europe are evaluated against
observations with a focus on sub-daily precipitation
statistics and the relation between extreme precipitation
and air temperature. A clear added value of the higher
resolution simulation is found especially in the
reproduction of the diurnal cycle and the hourly intensity
distribution of precipitation. Too much light precipitation
in the 12 km simulation results in a positive precipitation
bias. Largest differences between both resolutions occur in
mountainous regions and during the summer months with high
convective activity. Moreover, the observed increase of the
temperature–extreme precipitation scaling from the
Clausius-Clapeyron (C-C) scaling rate of $~7\%$ K-1 to a
super-adiabatic scaling rate is reproduced only by the 3 km
simulation. The effect of land surface heterogeneity on the
differences between 3 km and 12 km simulations is analysed
based on five WRF simulations for JJA 2003, each with the
same atmospheric setup in 3 km resolution but different
combinations of 12 km resolution land use and soil type,
initial soil moisture and orography. A coarser resolved
orography significantly alters the flow over and around
extensive mountain ridges like the Alps and impact the
large-scale flow pattern. The smoothed mountain ridges
result in weaker Föhn effects and in enhanced locally
generated convective precipitation pattern peaking earlier
in the afternoon. The effect of a coarser-resolved land use
distribution is overall smaller and mainly related to
changes in overall percentages of different land use types,
rather than to the loss of heterogeneity in the surface
pattern on the scale analysed here. Even small changes in
soil moisture have a higher potential to affect the overall
simulation results. WRF climate simulations downscaling the
MPI-ESM-LR data at 12 km and 3 km resolution for central
Europe are analysed for three 12-year periods: a control, a
mid-of-century and an end-of-century projection to quantify
future changes in precipitation statistics based on both
convection-permitting and convection-parameterized
simulations. For both future scenarios both simulations
suggest a slight decrease in mean summer precipitation and
an increase in hourly heavy and extreme precipitation in
large parts of central Europe. This increase is stronger in
the 3 km runs. Temperature–extreme precipitation scaling
curves in the future climate are projected to shift along
the $7\%$ K-1 trajectory to higher peak extreme
precipitation values at higher temperatures while keeping
their typical shape. The results of this thesis clearly
confirm the added value of convection-permitting climate
simulations, provide further insights into land-atmosphere
interaction processes and highlight the relevance of the
RCMs ability to properly simulate coupling strength.},
cin = {JSC},
cid = {I:(DE-Juel1)JSC-20090406},
pnm = {511 - Computational Science and Mathematical Methods
(POF3-511) / eLTER - European Long-Term Ecosystem and
socio-ecological Research Infrastructure (654359) / PhD no
Grant - Doktorand ohne besondere Förderung
(PHD-NO-GRANT-20170405)},
pid = {G:(DE-HGF)POF3-511 / G:(EU-Grant)654359 /
G:(DE-Juel1)PHD-NO-GRANT-20170405},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:5n-52545},
url = {https://juser.fz-juelich.de/record/858408},
}
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