讲座简介

Climate model simulations uniformly show drier and warmer summers in the Eurasian midcontinent during the mid-Holocene, which is not consistent with paleoenvironmental observations. The simulated climate results from a reduction in the zonal temperature gradient, which weakens westerly flow and reduces moisture flux and precipitation in the midcontinent. As a result, sensible heating is favored over evaporation and latent heating, resulting in substantial surface-driven atmospheric warming. Thus, the discrepancy with the paleoenvironmental evidence arises initially from a problem in the simulated circulation and is exacerbated by feedback from the land surface. This region is also drier and warmer than indicated by observations in the preindustrial control simulations, and this bias arises in the same way: zonal flow and hence moisture flux into the midcontinent are too weak, and feedback from the land surface results in surface-driven warming. These analyses suggest the need to improve those aspects of climate models that affect the strength of westerly circulation.

主讲人简介

Professor Sandy Harrison from the Department of Geography and Environmental Science, Reading University is interested in understanding the role of land-surface, terrestrial biosphere and hydrological processes in modulating regional climates, past, present and future. As a co-chair of the PalaeoclimateModellingIntercomparison Project (PMIP), Sandy has done lots of interesting work in reconstructing the past climate and environmental changes at continental to global scales, and using reconstructions in conjunction with climate-model experiments to diagnose the mechanisms of past climate and environmental changes. She is also a vegetation modeler with a specific emphasis on fire disturbance and vegetation emissions and analysis of plant traits with respect to climate.