Seasonal and Geographical Patterns of Lightning Incidence in New Mexico

Abstract Lightning has a transformative role in our environment and society. To understand the patterns of lightning incidence in the dry U.S. Southwest, where lightning is a prominent source of wildfires, we analyze 22 years of lightning incidence data in New Mexico (NM) collected by the U.S. National Lightning Detection Network (NLDN). Seasonality patterns indicate that most lightning happens in the afternoons of the months of July and August in NM and that lightning activity has been consistent over the span of two decades, displaying a minor decrease over time, correlated with a decrease in average precipitation. We present maps cross-referencing lightning occurrence with the state’s geography. Our analysis indicates lightning peaks in two types of regions. First, highest rates of cloud-to-ground (CG) lightning (including of positive polarity) seem to happen in a cluster of counties near the border with Texas in a geographic region known as the Great Plains. Roosevelt County (bordering Texas) has the highest CG lightning density at 4.2 flashes per square kilometer per year, while San Juan County in the northwest corner of the state has the lowest CG lightning density at 1.3 flashes per square kilometer per year. Second, secondary peaks in CG lightning density can also be found in forested mountains throughout the state, which include several national forests. The Gila National Forest and Lincoln National Forest have the highest rate of CG lightning incidence. Thus, they may be at greatest risk of lightning-ignited wildfires. Across most of the state, precipitation rates reasonably explain trends in lightning activity, but this correlation breaks down in NM’s lightning hotspot, the southeast corner of the state.