135 Atmospheric Dynamics of Massive Atmospheres

Tuesday, 27 June 2017
Salon A-E (Marriott Portland Downtown Waterfront)
Rei Chemke, Weizmann Institute of Science, Rehovot, Israel; and Y. Kaspi

Atmospheric dynamics of massive atmospheres:

The many recently discovered terrestrial exoplanets are expected to hold a wide range of atmospheric masses. Here the dynamic-thermodynamic effects of atmospheric mass on atmospheric circulation are studied using an idealized global circulation model by systematically varying the atmospheric surface pressure. On an Earth analog planet an increase in atmospheric mass weakens the Hadley cell circulation and decreases its latitudinal extent. These changes are found to be related to the reduction of the convective fluxes (due to an increase of the moist adiabatic lapse rate) and net radiative cooling (due to the higher atmospheric heat capacity), which respectively cool the upper troposphere at mid-low latitudes and warm it at high latitudes and low altitudes. These together decrease the meridional temperature gradient and increase the temperature lapse rate, which decreases the tropopause height. The reduction of these parameters, which play a key role in affecting the flow properties of the tropical circulation, weakens and contracts the Hadley circulation. The reduction of the meridional temperature gradient also decreases the extraction of mean potential energy to the eddy fields and the mean kinetic energy, which weakens the extratropical circulation. The decrease of the eddy kinetic energy decreases the Rhines wavelength, which is found to follow the meridional jet scale. The contraction of the jet scale in the extratropics results in multiple jets and meridional circulation cells as the atmospheric mass increases.

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