Hadley Circulation Response to Orbital Precession. Part II Subtropical Continent

• Published in: Journal of climate Vol. 26; no. 3; pp. 754 - 771
• Main Authors: Merlis, Timothy M., Schneider, Tapio, Bordoni, Simona, Eisenman, Ian
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01-02-2013
• Subjects: Angular momentum; Atmosphere; Atmospheric circulation; Atmospheric circulation models; Atmospheric energy balance; Atmospherics; Circulation; Continents; Earth, ocean, space; Eddies; Energy; Energy balance; Energy storage; Exact sciences and technology; External geophysics; Fluid circulation; Fluxes; General circulation models; General circulation. Atmospheric waves; Hadley circulation; Heat; Insolation; Marine; Meteorology; Momentum; Oceans; Orbitals; Perihelions; Perturbation; Precession; Precipitation; Radiation; Rainy seasons; Regions; Seasons; Simulation; Spatial variations; Specific heat; Summer; Summer circulation; Wind; Winter circulation; Northern Hemisphere; Atmosphere model; General circulation models; Ground surface; Orbital element; digital simulation; Forcing; Hadley cell; atmospheric circulation; subtropical zone; boundary conditions; precession
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/jcli-d-12-00149.1

The response of the monsoonal and annual-mean Hadley circulation to orbital precession is examined in an idealized atmospheric general circulation model with a simplified representation of land surface processes in subtropical latitudes. When perihelion occurs in the summer of a hemisphere with a subtropical continent, changes in the top-of-atmosphere energy balance, together with a poleward shift of the monsoonal circulation boundary, lead to a strengthening of the monsoonal circulation. Spatial variations in surface heat capacity determine whether radiative perturbations are balanced by energy storage or by atmospheric energy fluxes. Although orbital precession does not affect annual-mean insolation, the annual-mean Hadley circulation does respond to orbital precession because its sensitivity to radiative changes varies over the course of the year: the monsoonal circulation in summer is near the angular momentum-conserving limit and responds directly to radiative changes; whereas in winter, the circulation is affected by the momentum fluxes of extratropical eddies and is less sensitive to radiative changes.