Lightning and Associated Convection Features in the Presence of Absorbing Aerosols over Northern Alabama

Previous studies have suggested that positive correlations between aerosol concentration and lightning flash rate may be due to increased cloud condensation nuclei (CCN) and ice nuclei (IN) presence in deep convection. Interestingly, many of these studies are based on the thunderstorm cases in the presence of absorbing aerosols, which may also impact deep convection through their radiative effects. Lightning flashes from the Northern Alabama Lightning Mapping Array (NALMA) during the 1500 – 1800 Central Daylight Time (CDT) diurnal peak period are correlated with the aerosol optical depth (AOD) retrievals from the Moderate-resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite for summer storms during 2002–2015. Aerosol Index (AI) retrievals from the Ozone Monitoring Instrument (OMI) onboard the Aura satellite are used to separate non-absorbing and absorbing aerosols for deep convection case studies. A weak positive correlation was found between AOD and flash rate, which may be due to the association between aerosol loading and lightning-producing storms in area. However, it is found that no correlation is present between AOD and flash rate per storm, though a correlation is observed between flash rate and surface-based Convective Available Potential Energy (CAPE). The study also found that lightning has a stronger correlation with absorbing aerosols than non-absorbing aerosols, particularly in the low CAPE regime, suggestive of a potentially stronger regulation by absorbing aerosols if aerosol impacts on lightning are present. Absorbing aerosols also show a weak negative correlation with the planetary boundary layer height (PBLH), suggesting that the interaction between absorbing aerosols and turbulent mixing may contribute to the regulation of lightning-producing storms. In addition, a capping inversion caused by absorbing aerosols may lead to the accumulation of CAPE, as suggested by an increased correlation between absorbing aerosols and CAPE. The impacts of aerosols on lightning are intertwined with other background environmental conditions, but if present, may result from a synthesis of multiple mechanisms related to both microphysical and radiative effects of aerosols.