Diurnal Temperature Variability: An Observations–Climate Model Intercomparison

Surface temperature measurements since the mid-20^thcentury 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. Through linear regression of DTR on specific humidity, we derived an empirical model for predicting DTR variability with respect to changes in future water vapor concentrations. This was used to estimate how the diurnally asymmetric warming trend may continue and interact with global warming. We further assess 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 are proposed to be associated with inaccuracies in GCM-simulated water vapor concentrations. This may be symptomatic of limitations in the physical parameterizations of cloud and precipitation processes, warranting further investigation to increase the reliability of global warming projections.