83rd Annual

Monday, 10 February 2003
Mountain uplift and ENSO
Akio Kitoh, MRI, Tsukuba, Ibaraki, Japan
Poster PDF (2.3 MB)
To study the effect of mountain uplift on the global climate system, a series of coupled GCM experiments were performed. We used eight different mountain heights: 0% (no mountain), 20%, 40%, 60%, 80%, 100% (control run), 120%, and 140%. Land-sea distribution is the same for all experiments and all mountains in the world are uniformly varied. The model used is the new MRI coupled GCM (MRI-CGCM2). The model consists of a T42 L30 AGCM and a global 0.5-2.0 by 2.5 L23 OGCM. Each run is integrated without flux adjustments for 50 years, for which the last 40 yearsŐ data are analyzed.

The intensity of the Pacific subtropical anticyclone and associated trade winds became stronger with mountain height, while the South Asian monsoon westerly almost saturated at around the 80% mountain height. These two compensating effects determine the divisions of Asia-Pacific monsoons. The structure of the Pacific warm pool and the ENSO behavior also systematically changed by mountain height changes. When the mountain height is low, a warm pool is located over the central Pacific due to weakened trade winds in the Pacific. The model El Nino is the strongest, frequency is long and most periodic in the 0% run. They become weaker, shorter and less periodic when the mountain height increases.

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