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

Abstract

Many of the previous aerosol-convection/lightning enhancement studies are based on convective storms that occur in the presence of absorbing aerosols; such aerosols may impact deep convection through their microphysical and radiative effects. In this study, lightning flash rates (FRs) are analyzed together with aerosol optical depth (AOD) retrievals from the Moderate Resolution Imaging Spectroradiometer for summer storms during 2002–2015. Aerosol index retrievals from the Ozone Monitoring Instrument are used to separate nonabsorbing and absorbing aerosol cases. Statistical analyses are performed to test for significant sample differences and linear relationships between the AOD of case studies and the FRs, convective available potential energy, planetary boundary layer height, and low-level vertical wind shear to identify if evidence of regulation of storms by absorbing aerosols exists. Overall, AOD and FR do not show any significant linear relationship. When just observing absorbing aerosols, however, AOD and FR show a stronger (but still very weak) positive correlation. The weak correlation may be related to the absorbing aerosols' impact on convective available potential energy, which has a moderate linear correlation to AOD particularly when the instability is low, which implies some kind of convection or convective environment modification by absorbing aerosols. Although the planetary boundary layer height tends to decrease with increasing amount of absorbing aerosols, it is found that low-level vertical wind shear does not correlate with AOD for either absorbing or nonabsorbing aerosols. This result suggests little influence of the interaction between absorbing aerosols and turbulent mixing on storms.