Regional and temporal variability of orographic influence on subdaily precipitation intensity in Colorado

The influence of mountains on precipitation processes can produce distinct spatial patterns in climatology. These relationships are often used to inform interpolation between precipitation observations in mountainous areas. At the event scale, the control of orography on precipitation is more variable and less understood than long term rainfall patterns. Anomalous precipitation events and variation at subdaily time scales are likely omitted from gage-based datasets due to low station density. Here, we use several remotely-sensed and model-derived hourly datasets to explore the influence of terrain on the magnitude of subdaily precipitation intensity throughout Colorado. Terrain effects on precipitation vary sharply across Colorado and shift with season and accumulation period, so interpolated datasets or frequency analyses based on simple linear regressions can overlook critical extremes, especially at fine spatial scales in mountainous regions. Precipitation–elevation relationships differ among basins: the Missouri and Arkansas show decreasing precipitation with elevation—an effect stronger for hourly than daily totals—whereas the Colorado and Rio Grande exhibit increasing precipitation with elevation, with daily totals rising more steeply and significantly than hourly ones. Gage‑based frequency studies, limited by sparse networks, miss the frequency of high intensity clusters along the Front Range and Pikes Peak shown by gridded model data.