IROAM: IPRC Regional Ocean-Atmosphere Model

The climate of the eastern Pacific plays an important role in the El Niño-Southern Oscillation and thus in global climate. This region, though, has been notoriously difficult to simulate realistically in climate models. IPRC researchers have developed a model, the iROAM (IPRC regional ocean-atmosphere model) that couples the IPRC regional atmospheric model (IPRC Climate, Vol. 2, No. 2) with the GFDL Modular Ocean Model. The ocean model covers the entire tropical Pacific, and the atmospheric model covers the eastern half of the Pacific as well as Central America and most of South America. In collaboration with the Kyousei-7 Project at the Frontier Research Center for Global Change (Frontier), the model has been adapted to run on Japan's Earth Simulator. The iROAM has successfully captured the salient features of eastern Pacific climate that have been so difficult to simulate, including the northward displaced intertropical convergence zone (ITCZ) and the equatorial annual cycle. As in observations, the model ITCZ stays north of the equator most of the year except for a brief period in March and April when equatorial sea surface temperatures reach their annual maximum. IPRC Climate, Vol. 6, No. 1