Evaluation of a present-day climate simulation with a new coupled atmosphere-ocean model GENMOM

Abstract

Abstract. We present a new, non-flux corrected AOGCM, GENMOM, that combines the GENESIS version 3 atmospheric GCM (Global ENvironmental and Ecological Simulation of Interactive Systems) and MOM2 (Modular Ocean Model version 2). We evaluate GENMOM by comparison with reanalysis products (e.g., NCEP2) and eight models used in the IPCC AR4 assessment. The overall present-day climate simulated by GENMOM is on par with the models used in IPCC AR4. The model produces a global temperature bias of 0.6 °C. Atmospheric features such as the jet stream structure and major semi-permanent sea level pressure centers are well simulated as is the mean planetary-scale wind structure that is needed to produce the correct position of stormtracks. The gradients and spatial distributions of annual surface temperature compare well both to observations and to the IPCC AR4 models. A warm bias of ~2 °C is simulated by MOM between 200–1000 m in the ocean. Most ocean surface currents are reproduced except where they are not resolved well by the T31 resolution. The two main weaknesses in the simulations is the development of a split ITCZ and weaker-than-observed overturning circulation.