Spatial variability of rainfall in the Colorado Rocky Mountains: A comparison of radar-derived and rain gauge data

Study Region Flash floods in the Colorado Rocky Mountains, USA are triggered by intense rainfall during convective storms, and the likelihood and severity of flash flooding increases following wildfires. Middle elevations (∼1500–2500 m) have experienced the largest flash floods in the past, causing researchers to speculate that rainfall intensity may vary with elevation. Study Focus This study combines Multi-Radar/Multi-Sensor System (MRMS), Parameter-elevation Regressions on Independent Slopes Model (PRISM), and Gridded Surface Meteorological (gridMET), and tipping bucket precipitation datasets to evaluate how warm season rainfall intensities vary with elevation and side of the mountain range in northern Colorado. The MRMS data are compared with tipping bucket gauges to evaluate which data source best predicts streamflow occurrence. New Hydrological Insights for the Region The east side of the mountain range experienced both higher warm season total precipitation and rainfall intensities than the west side during 2021–2023. The relationship between elevation and rainfall intensity was inconsistent between years, indicating no strong elevation effect on rainfall intensity. MRMS rainfall intensities predicted binary streamflow occurrence as accurately as tipping buckets east of the mountains in wildfire-affected areas, whereas tipping buckets performed significantly better to the west due to poor radar coverage. The MRMS dataset may outperform tipping buckets for detecting storms that trigger stream occurrences in areas with high radar coverage, due to its broader spatial coverage than most gauge networks.