Download High resolution RCM simulation of eastern Mediterranean climate

High resolution RCM simulation of eastern Mediterranean climate and its expected
changes to 2050
Simon O. Krichak
Department of Geophysics and Planetary Sciences, Faculty of Exact Sciences, Tel Aviv
University ([email protected])
Abstract
The eastern Mediterranean (EM) region is found in a transition zone between the aridclimate part of North Africa and the central Europe, which is characterized by temperate
and rainy conditions. Due to its geographical location, the EM is affected by both the
mid-latitudinal processes and those of the tropical zone. The sensitivity of the EM climate
to the effects of the both climatic zones imposes additional requirements to the ability of
the climate models to describe the effects.
Modern global climate change evaluations usually based on application of coupled
atmosphere-ocean global climate models (AOGCM). Contemporary European AOGCM
models are characterized by quite coarse (~200 km) space resolution, which precludes
them from representing effects of small scale processes. Different scenarios of
anthropogenic emission of greenhouse gases (GHG), have been designed for such studies
by the Intergovernmental Panel on Climate Change (IPCC). A number of different
anthropogenic emission scenarios have been developed by the IPCC. Within the full
range of the IPCC scenarios, A1B (IPCC 2007) expects medium-high increase of
CO 2 concentration to about 700 ppm by 2100 and carbon emissions. The mixing of the
CO 2 into the deep ocean maintains a slow surface ocean CO 2 increase, so in A1B the
oceanic sink steadily increases. Also in A1B, fossil fuel emission increases until 2050
and decreases thereafter. Significantly less intense GHG anthropogenic emission is
expected in B1 scenario, under which the CO 2 concentrations will increase only to about
550 ppm by 2100. Also in case of the B1 scenario fossil fuel emission is expected to
increase until 2050 and decrease thereafter.
Accuracy of representation of the EM climate (as well as the consequences of its
variations nearby) with the AOGCM's is significantly limited by insufficient space
resolution as well as by lack of the accuracy in description of effects of sub-grid
processes. It is a widely accepted strategy to perform regional downscaling of AOGCM
results by using them to drive regional climate model (RCM) simulations. A research
effort on RCM simulation of the EM climate and its expected changes to 2050 due to
anthropogenic increase of concentration of greenhouse gases is currently in process of
realization at Tel Aviv University. The RCM model used in the effort is a state of
science, third generation RegCM3 model (Pal et al. 2007) of the International Center for
Theoretical Physics (ICTP) [http://users.ictp.it/RegCNET/]. Dynamical component of the
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RegCM3 model originates from those of hydrostatic version of compressible finitedifference NCAR/Penn State model MM5 using vertical sigma-coordinate system to
account for topography effects.
The experiment consists of the RegCM3 downscaling of results of global climate change
experiments performed with two European AOGCM models – ECHAM5 of the MaxPlank Institute for Meteorology in Hamburg, Germany and HadCM3Q of the Met Office
Hadley Centre for Climate Prediction and Research, UK. The RCM simulations currently
in progress are performed at the Computational Center of Tel Aviv University using a
cluster system running CentOS release 4.5 (using the space resolution of 25 km/18 levels)
and Cray XT5 computer of the Swiss National Supercomputing Centre CSCS (14 km
space resolution)
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