Intracloud Lightning Activity during a Late Spring Season Polluted Dryline Convective Event

Lightning activity is often used as a proxy for deep convective cloud development. Cloud-to-cloud (IC) and cloud-to-ground lightning (CG) strokes can be good indicators of updraft strength, ice particle concentration, cloud electrification structure, and likelihood of severe weather type (e.g., tornado, large hail, severe winds). Aerosol perturbations have been known to influence cloud electrification since they impact cloud microphysical properties such as cloud condensation nuclei (CCN) and ice nuclei (IN) number concentrations. Positive polarity CG lightning strokes, at times, show good agreement with violent severe weather types (e.g., EF2+ tornadoes and 3+ inch diameter hail). Recent studies have shown that these particular events can be (but not always) observed downwind from massive wildfires which release large amounts of biomass burning smoke aerosols. These aerosols readily activate as CCN and subsequently, IN as they are lofted above the freezing level of the deep convective cloud. Thus, a complex combination of dynamics, thermodynamics, and aerosol perturbation can sometimes result in anomalous positive polarity CG lightning. However, information from IC lightning is also useful. A dry line convective event in early June 2018 was chosen to show how IC lightning can be used as a proxy for the complex interactions of physical and microphysical processes in addition to aerosol loading. Preliminary results revealed that negative polarity IC lightning dominated the total lightning stroke count in the northern region (Nebraska) while positive polarity IC lightning dominated in the central and southern regions (Texas panhandle and Rio Grande valley). Four large wildfires (Colorado, New Mexico (2 fires), and Chihuahua, MX) seeded the region prior to dry line development, and a northward decreasing aerosol loading gradient was observed. In addition, the storms in the northern region quickly linearized to a quasi-linear convective system while the central and southern convection remained primarily as discrete and a mixture of discrete-multicellular mode thunderstorms, respectively. Though there were jumps in total lightning activity preceding many of the observed severe weather events, the reversal of IC lightning polarity dominance along the dry line is noteworthy and worth further investigation.