| Popis: |
Surface temperature measurements since the mid-20thcentury have revealed a diurnally asymmetric global warming trend, with nighttime minimum temperatures increasing faster than daily maxima. The result is an overall decrease in the diurnal temperature range (DTR), which has implications for agriculture, streamflow, winter sports, as well as the overall magnitude of global warming. We begin with an assessment of the fidelity of global climate model (GCM)-simulated DTR baseline estimates between 2007 and 2016 through comparison with similar calculations using modern atmospheric reanalysis data. Significant deviations between observed and GCM-simulated baseline DTR, largely characterized by an overestimate of DTR by GCMs, are proposed to be associated with inaccuracies in GCM-simulated water vapor concentrations, as DTR is known to be closely related to atmospheric water vapor concentration. Further, through linear regression, we built an empirical model for predicting DTR variability with respect to changes in specific humidity. This was used to derive an alternative approach to projecting how the diurnally asymmetric warming trend may continue and interact with global warming. Such projections indicate that DTR will decline by 1-2˚C over global land regions and by ~0.5˚C over the global oceans. Model biases in DTR may be symptomatic of other limitations such as the physical parameterizations of cloud and precipitation processes, warranting further investigation to increase the reliability of global warming projections. |
