125 Climate Dependencies on Obliquity and Radiative Timescales

Tuesday, 27 June 2017
Salon A-E (Marriott Portland Downtown Waterfront)
Ilai Guendelman, Weizmann institute of science, Rehovot, Israel; and Y. Kaspi

The discovery of planets beyond our Solar System is one of the most exciting scientific developments of the last 20 years.
These planets differ by many orbital and atmospheric parameters such as their atmospheric mass, radius, rotation rate, composition, stellar flux, gravitational acceleration, eccentricity, obliquity.
Variability in these parameters will result in different atmospheric circulation.
In this work we look at the response of the zonal mean circulation to changes in obliquity and orbit period using an idealized GCM.
Obliquity that differs from zero introduces seasonality, increasing obliquity will increase the temperature gradient between winter and summer hemispheres, which results in widening and strengthening of the winter Hadley cell.
Changes in the orbital period of a planet, keeping the same solar constant (can represent a specific habitable zone solar flux for different solar systems), gives change in the seasonality timescale, where for longer periods the atmosphere has more time to adjust to the solar forcing, increasing the strength of the circulation and widening of the Hadley cell as well.
Both obliquity and orbital period changes affect the location of the ITCZ, yet even for long orbital period it does not reach the warmest summer latitude at high obliquities.
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