Mid-Holocene precipitation changes in the South Pacific Convergence Zone
Abstract
The variability of the South Pacific Convergence Zone (SPCZ) during the Mid-Holocene is investigated using models archived in the Paleoclimate Modeling Intercomparison Project Phase II (PMIP2) database. Relative to present day (or preindustrial) conditions, mid-Holocene top-of-the-atmosphere insolation was relatively lower during austral summer (December-January-February, DJF), which is the season during which the SPCZ is at its peak intensity in current climate. In response to this perturbation, the PMIP2 models reflect a displacement of the SPCZ to the southwest. Decomposing the DJF precipitation changes in terms of a diagnostic moisture budget indicates a complex interplay of processes, involving changes in both thermodynamics and dynamics as well as mean and eddy components of the circulation. Idealized experiments performed with the Quasi-equilibrium Tropical Circulation Model (QTCM), an intermediate level complexity model, suggests that the direct effect of reduced insolation primarily impacts the tropical portion of the SPCZ as a remote response to the weakening of the austral summer Australian monsoon. On the other hand, the SPCZ shift at higher latitudes appears to be more strongly tied to SST changes induced by insolation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP41A1990M
- Keywords:
-
- 3305 ATMOSPHERIC PROCESSES / Climate change and variability;
- 3319 ATMOSPHERIC PROCESSES / General circulation;
- 3371 ATMOSPHERIC PROCESSES / Tropical convection;
- 3373 ATMOSPHERIC PROCESSES / Tropical dynamics