Objectives

Climate change experiments summarized in the IPCC AR4 report were performed at a
resolution that is too low to resolve regional phenomena such as high-impact weather
events, hurricanes, intense mid-latitude cyclones, coastal dynamics, and topographically
constrained oceanic circulation features. Moreover, the AR4 simulations could not
represent two classes of variability, namely internal gravity waves in the atmosphere and
meso-scale eddies in the ocean. The former represents an important member in the
chain relating atmospheric variability on a vast range of scales that is crucial for the
interaction between the troposphere and the stratosphere. The latter represents the bulk
of oceanic variability on intra-seasonal time scales that is essential for the turbulent
motions in the oceanic interior and consequently for the ocean general circulation,
including the global meridional overturning circulation. Both classes of variability and
other small-scale high-impact phenomena can interact with global-scale processes,
such as meridional and vertical energy and water transports in the atmosphere and
ocean, and from that alter the climate sensitivity to increases in GHG concentration.
The STORM project proposes long climate change simulations (i.e. over several
centuries) at a horizontal and vertical resolution that is high enough to allow the
development of gravity waves in the atmosphere, meso-scale eddies in the ocean, and
other small-scale high-impact phenomena. By doing so, new types of scale-coupling and
scale-interactions are introduced into the climate simulation. The model will be the latest
version of the COSMOS model including ECHAM6 and MPIOM, but without
biogeochemistry modules.

The horizontal resolution in the atmosphere will be T255. To resolve gravity waves and
to allow the coupling between the troposphere and the stratosphere through these waves,
the ECHAM model will be extended vertically to the height of the middle atmosphere
at about 80 km (MAECHAM) with a vertical resolution of about 500-600 meters (i.e. with 199 layers).

To adequately represent inertial currents, resolve important topographic features, and simulate
the meso-scale eddies in the ocean, a horizontal ocean resolution of at least 0.1° (TP6M) will be used.
The ocean model will have 80 vertical levels. Following a control run
of about 50 to 100 years with constant pre-industrial levels of greenhouse gases, a
simulation of the 20th century from year 1890 to 2005 using the observed anthropogenic
and natural forcing, and a climate change projection using one of the IPCC AR5
scenarios (RCP4.5) from 2005 to 2100 will be performed.