Polar and Topographic Amplifications of Intermodel Spread of Surface Temperature in Climate Models

The spatial pattern of intermodel spread of surface temperature (TS-SPREAD) is similar to the absolute error of modeled surface temperature relative to observations, implying the possibility of using intermodel spread to understand the model biases. The regions with maximum TS-SPREAD are located in the northern polar (NP) and southern polar (SP) regions, and regions with the large orographic features, such as the Tibetan Plateau (TP). We find: (a) Winter amplification exists in the TS-SPREAD over both the NP and SP regions, but the maximum TS-SPREAD over the TP happens during spring and summer with weak seasonality there. (b) Surface energy balance analyses show salient land-sea contrast in the interlinkage between the physical processes. (c) Over the Arctic Ocean and the Southern Ocean, the maximum spreads of sea-ice-induced surface albedo appear during summer when the TS-SPREADs are the weakest because the effect of surface albedo is offset by the heat storage in the oceans. (d) Through the interseasonal linkage of the heat storage term, i.e., the summer-storing-winter-releasing of oceanic heat content, the summer surface albedo may indirectly contribute to the winter amplification of the TS-SPREAD over the polar oceans. Such interseasonal linkage of the processes does not exist over the land areas. A method of distinguishing the roles of the local and nonlocal dynamical processes in the contribution of the clear-sky downward longwave radiation to the TS-SPREAD is also provided.