Extreme Precipitation-Temperature Scaling in California: The Role of Atmospheric Rivers

The sensitivity of atmospheric river (AR)-induced precipitation to climate change is primarily driven by increases in atmospheric water vapor with warming. However, the rate at which AR-based precipitation intensifies with warming and whether this rate differs from non-AR events remains uncertain. This work uses multiple statistical models to estimate regional, extreme precipitation-temperature scaling rates in California for AR and non-AR events. Scaling rates are determined using cold-season daily and hourly precipitation, along with multiple temperature variables to assess robustness of the results. We find that regional scaling rates for ARs are consistently larger than non-ARs, especially for hourly event maxima (posterior median scale rates of 5.7% and 2.4% per & DEG;C for ARs and non-ARs, respectively). ARs remain near saturated (i.e., high relative humidity) and exhibit more lift and a stronger increase in specific humidity aloft with warming as compared to non-ARs, helping to explain the difference in precipitation-temperature scaling rates.

Automated summary

The sensitivity of AR-induced precipitation to climate change is primarily driven by increases in atmospheric water vapor with warming. This study examines the scaling rates of extreme precipitation with temperature for AR and non-AR events in California using multiple statistical models. The results show that the regional scaling rates for ARs are consistently larger than non-ARs, especially for hourly event maxima. This difference in scaling rates can be explained by the fact that ARs remain near saturated and exhibit more lift and a stronger increase in specific humidity aloft with warming compared to non-ARs.