Exoclimes_Conference_booklet1

pressure.The Bcool project is an international collaboration studying the
magnetic fields of solar-type stars and whose results can be used for
stellar wind studies. Using a simple wind model we show that an exoplanet
like the present-day Earth would generally need to orbit outside the
traditional habitable temperature zone of many solar-type stars to
maintain the size of its magnetosphere. However, planets orbiting within
the classical temperature habitable zone of solar-type stars should
possess magnetospheres that although compressed, are likely to protect the
planet's atmosphere and hence allow for the planet to be habitable.
An aqua planet under strong solar forcing!
Max Popp — Max Planck Institute for Meteorology
A modified version of the general circulation model ECHAM6 is used to investigate the
impact of increased total solar irradiance (TSI) on an aqua planet on a present-day Earthlike
orbit. We find that the present-day Earth-like climate destabilizes for a TSI between
1.06 and 1.08 times the present-day Earth value (S0). The aqua planet does not, however,
go into a Runaway Greenhouse, but attains a new steady state with global-mean seasurface
temperatures exceeding 335 K. This warm state is characterized by a low
meridional temperature gradient, a weak meridional circulation without polar cells, a moist
stratosphere and convection-dominated cloud formation. As the TSI is further increased,
the planet remains in the same regime of warm steady states for TSIs of at least up to 1.2
S0, because the cloud albedo increases as well, and balances the increased forcing. In
these states, the volume mixing ratio of water vapor in the upper atmosphere may attain
values as large as 0.015. This large mixing ratio exceeds the “Moist Greenhouse” limit
(Kasting et al. 1993) and suggests that a planet in such a warm state would hence be
subject to a rapid loss of water.
Climate dynamics of a coupled Aquaplanet
Josiane Salameh — Max Planck institute for Meteorology
The idea behind an Aquaplanet, an idealized configuration of the current Earth with all the
landmasses removed, is not recent. However, most of the research is conducted with
stand-alone atmospheric models. Thus, the originality behind considering the coupled
Aquaplanet setup, highlights the ocean's impact and allows us to directly interpret the
fundamental processes and feedbacks between ocean and atmosphere without any land
interference.
As for the few coupled Aquaplanet studies lately conducted on General Circulation
Models (GCM), they showed an extreme disparity regarding the final climate state. The
range of states discovered lies between a warm climate qualified with a lack of sea-ice
formation and a cold climate where sea-ice extend at the poles. Then, the existence of
three equilibrium states was verified while integrating the same GCM from different
random initial conditions.
The climate of a coupled Aquaplanet remains an open question. Therefore, our task is to
analyze the atmospheric-oceanic circulations of a coupled Aquaplanet while contributing to
this discrepancy in previous results. The simulations are executed on “ICON”, based on an
icosahedral triangular grid. Effects of rotation on Hadley cell's magnitude and extent, winds
distribution and others were already theoretically discussed and numerically tested. In
order to achieve a higher physical understanding of the Earth rotation rate and its effect on
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