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.