SGER: Role of the Indian Ocean in Causing the Excessive Biennial El Nino-Southern Oscillation (ENSO) Tendency in NCAR's Community Climate Modeling System (CCSM3) Simulations

University Of California-Irvine, Irvine CA

Investigators

Abstract

Many coupled climate models, those with full representations of the atmosphere and ocean, are unable to simulate accurately the spatial structure and time evolution of the El Nino/Southern Oscillation (ENSO) phenomenon. ENSO is a leading mode of climate variability that affects regional weather and climate over much of the world. The current version of the Community Climate System Model (CCSM3) at the National Center for Atmospheric Research (NCAR) produces ENSO variability, but with an unrealistically strong two-year, or biennial, cycle. This deficiency, in one of the leading models used for projections of global climate change, reduces the reliability of such projections and their utility for predicting changes in regional climates. Based on his earlier model studies the PI hypothesizes that this unrealistic temporal variability in ENSO is a result of interactions between the tropical Pacific and Indian Oceans. He will test this hypothesis by conducting model experiments in which, rather than simulating sea-surface temperatures in the Indian Ocean, temperatures in this basin are imposed; the imposed temperatures will follow both a model generated and an observed annual cycle. If the excessive biennial variability of ENSO is reduced or eliminated in these experiments, it will indicate that the Indian Ocean climate is a significant source of the problem in the full model. This work will help to correct an important problem in a widely used, state-of-the-art, climate model and will contribute to training a graduate research assistant.