资源环境科技发展态势分析平台

Observed surface temperature distributions are non-Gaussian, which has important implications for the likelihood of extreme events in a changing climate. We use a two-dimensional advection-diffusion model of temperature stirred by stochastically generated Rossby waves with a sustained background temperature gradient to explore non-Gaussian temperature distributions. We examine how these distributions change with changes to thermal relaxation and eddy stirring. Weakening the background temperature gradient leads to decreased variance but no changes in other moments, while the eddy properties affect both the variance and skewness. A poleward movement of eddy stirring latitude leads to reduced skewness for most latitudes, implying a shift toward longer negative tails in temperature distributions, all else being equal. In contrast, the dependence of temperature skewness on eddy speed is a nuanced, nonlinear relationship.

Plain Language Summary Global warming is expected to cause changes in extreme events. In this study, we use a simple model to explore how local extreme temperatures change with changes to large-scale wind and temperature patterns. Particularly, we are interested in the reasons that some regions have more extreme cold events than extreme warm events (and vice versa) and whether or not that asymmetry between hot and cold events will change. Although the model presented in this study is very simple, it qualitatively captures the statistics of present-day temperatures and may be regarded as a prototype for our understanding of how thermal and circulation changes impact extreme values. Our results show that the shifts in the circulation expected with global warming change both how often extreme temperatures occur and the asymmetry between hot and cold extremes. These results suggest caution in applying present-day temperature statistics to predicting future extremes.