The effects of orbital precession on tropical precipitation: Mechanisms controlling precipitation changes over land and ocean
The tropical precipitation response to precessional forcing is investigated using idealized precession experiments from the Geophysical Fluid Dynamics Laboratory Coupled Model version 2.1 and mid-Holocene experiments from ten general circulation models participating in the Paleoclimate Modeling Intercomparison Project Phase III. Both sets of experiments show a seasonal land-ocean asymmetry in the tropical precipitation response: precipitation increases over land and decreases over ocean in the season with increased insolation and the opposite is true in the season with decreased insolation. This response is examined using a framework that describes how changes in net top-of-atmosphere radiation affect the atmosphere and surface energy balances. Over land, surface energy storage is small and changes in precipitation are balanced by changes in moist static energy flux divergence. Over ocean, surface energy storage is large, moist static energy flux divergence is small, and changes in precipitation are ultimately driven by changes in circulation and atmospheric stability.
Additional InformationWe would like to thank Michael Erb and Tony Broccoli for providing the data for the GFDL-CM2.1 idealized simulations. Data is available from K.A.C. upon request and additionally, the PMIP3 data can be found online at http://pcmdi9.llnl.gov/esgf-web-fe/. This study was supported by the National Science Foundation Paleo Perspectives on Climate Change program.
Submitted - Chamales_FINAL.pdf