Responses of Extreme Discharge to Changes in Surface-Air and Dewpoint Temperatures in Utah: Seasonality and Mechanisms

The changes in stream discharge extremes due to temperature and seasonality are key metrics in assessing the effects of climate change on the hydrological cycle. While scaling is commonly applied to temperature and precipitation due to the physical connections between temperature and moisture (i.e., Clausius-Clapeyron), the scaling rate of stream discharge extremes to air and dewpoint temperatures has not been evaluated. To address this challenge, we assess the scaling rates between stream discharge and air temperature and between stream discharge and dewpoint temperature in Utah using a well-designed statistical framework. While there are deviations from the Clausius-Clapeyron (CC) relationship in Utah using discharge data based on stream gauges and gridded climate data, we identify positive scaling rates of extreme discharge to temperatures across most of the state. Further diagnosis of extreme discharge events reveals that regional factors combined with topography are responsible for the marked seasonality of scaling, with most areas of Utah driven by spring snowmelt tied to high temperatures. The exception is far southwestern areas, being largely driven by winter rain-on-snow events. Our research highlights a measurable portion of stream discharge extremes associated with higher temperatures and dewpoints, suggesting that climate change could facilitate more extreme discharge events despite reductions to mean flows.

Automated summary

The changes in stream discharge extremes due to temperature and seasonality are important indicators of the effects of climate change on the hydrological cycle. We evaluated the scaling rates between stream discharge and air temperature and between stream discharge and dewpoint temperature in Utah, and found a positive correlation between extreme discharge and temperature in most areas.