Hadley Circulation Response to Orbital Precession. Part I: Aquaplanets
The response of the monsoonal and annual-mean Hadley circulation to orbital precession is examined in an idealized atmospheric general circulation model with an aquaplanet slab-ocean lower boundary. Contrary to expectations, the simulated monsoonal Hadley circulation is weaker when perihelion occurs at the summer solstice than when aphelion occurs at the summer solstice. The angular momentum balance and energy balance are examined to understand the mechanisms that produce this result. That the summer with stronger insolation has a weaker circulation is the result of an increase in the atmosphere's energetic stratification, the gross moist stability, which increases more than the amount required to balance the change in atmospheric energy flux divergence necessitated by the change in top-of-atmosphere net radiation. The solstice-season changes result in annual-mean Hadley circulation changes (e.g., changes in circulation strength).
Additional Information© 2013 American Meteorological Society. Manuscript received 6 December 2011, in final form 24 July 2012. A careful reading of Tim Merlis's Ph.D. thesis by Andy Thompson is greatly appreciated. We thank Rob Korty and Damianos Mantsis for helpful comments on the manuscript. This work was supported by a National Science Foundation Graduate Research Fellowship, a Princeton Center for Theoretical Science Fellowship, and National Science Foundation Grant AGS-1049201. The program codes for the simulations, based on the Flexible Modeling System of the Geophysical Fluid Dynamics Laboratory, as well as the simulation results themselves, are available from the authors upon request.
Published - jcli-d-11-00716.1.pdf