Outsize Influence of Central American Orography on Global Climate

Global Climate Models (GCMs) exhibit substantial biases in their simulation of tropical climate. One particularly problematic bias exists GCMs' the rainband known as Intertropical Convergence Zone (ITCZ). Much precipitation on Earth falls within ITCZ, which plays a key role setting Earth's temperature by affecting global energy transports, and partially dictates dynamics largest interannual mode climate variability: The El Niño-Southern Oscillation (ENSO). Most GCMs fail to simulate mean state ITCZ correctly, often exhibiting “double bias,” with rainbands both north south rather than just equator. These limit confidence models' projected future paleoclimate states, reduce utility these models for understanding present dynamics. Adjusting GCM parameterizations cloud processes atmospheric convection can biases, artificially correcting sea surface temperatures through modifications air-sea fluxes (i.e., “flux adjustment”). Here, we argue that significant portion rainfall circulation are rooted orographic height being biased low due assumptions made fitting observed orography onto grids. We demonstrate making different, physically defensible, raise significantly improves model climatological features such North American well ENSO. findings suggest simple, based, computationally inexpensive method improve projections