Meteorological and geographical factors associated with dry lightning in central and northern California

Abstract Lightning occurring with less than 2.5 mm of rainfall—typically referred to as ‘dry lightning’—is a major source wildfire ignition in central and northern California. Despite being rare, dry lightning outbreaks have resulted destructive fires this region due the intersection dense, vegetation large population living adjacent fire-prone lands. Since thunderstorms are much common relative interior West, climatology drivers not been widely investigated Using daily gridded precipitation observations (1987–2020) combination atmospheric reanalyses, we characterize associated meteorological conditions during warm season (May–October) when risk is highest. Across domain, nearly half (?46%) all cloud-to-ground flashes occurred study period. We find that higher elevations (>2000 m) receive more compared lower (<1000 activity concentrated July-August. Although local show substantial spatial variation, regionwide enhancements mid-tropospheric moisture instability on days background climatology. Additionally, surface temperatures, lower-tropospheric dryness, increased across versus wet days. also identify widespread historical record, quantify their seasonality extent, analyze large-scale patterns. Three these four patterns characterized by different configurations ridging over continental offshore troughing. Understanding meteorology can inform forecasting possible ignitions relevant for assessing changes climate projections.