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  • Joseph, R., and S. Nigam, 2006: ENSO Evolution and Teleconnections in IPCC’s 20th Century Climate Simulations: Realistic Representation?. J. Climate. Accepted.

The study focuses on assessment of the spatio-temporal structure of ENSO variability and its winter climate teleconnections to North America in the IPCC AR4 simulations of 20th century climate. The 1950-1999 period simulations of six IPCC models [GFDL CM2.1, GISS-EH, CCSM3, PCM, HADCM3 and MIROC3.2 (hires)] are analyzed in an effort to bench-mark models in simulation of this leading mode of interannual variability.

The standard deviation of monthly SST anomalies is maximum in the Nino3 region in all six simulations, indicating progress in modeling of ocean-atmosphere variability. The broad success in
modeling ENSO’s SST-footprint – quite realistic in CCSM3 – is however tempered by the difficulties in modeling ENSO evolution: Biennial oscillation in CCSM3, and no regular warm-to-cold phase transition in the MIROC model. The spatio-temporal structure, including seasonal phaselocking, is on the whole, well modeled by HADCM3; but there is room for improvement, notably, in modeling the SST foot-print in the western Pacific.
ENSO precipitation anomalies over the tropical Pacific and links to North American winter precipitation are also realistic in the HADCM3 simulation; and, to an extent, in PCM. Hydroclimate teleconnections that lean on stationary component of the flow, such as surface air temperature
links, are however not well modeled by HADCM3 since the midlatitude ridge in the ENSO response is incorrectly placed in the simulation; PCM fares better.
The analysis reveals that climate models are improving but still unable to simulate many features of ENSO variability and its circulation and hydroclimate teleconnections to North America. Predicting regional climate variability/change remains an onerous burden on models.

Full Article: http://www.atmos.umd.edu/~nigam/renu.enso.rev.pdf

Last Updated: 2006-03-02

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