Anvil microphysical signatures associated with lightning-produced NO_x

Abstract. Thunderstorm anvils were studied during the Deep Convective Clouds and Chemistry experiment (DC3), using in situ measurements and observations of ice particles and NO_x together with radar and Lightning Mapping Array measurements. A characteristic ice particle and NO_x signature was found in the anvils from three storms, each containing high lightning flash rates in the storm core prior to anvil sampling. This signature exhibits high concentrations of frozen droplets (as measured by a Cloud Droplet Probe) coincident with lower NO_x on the edges of the anvil. The central portion of these anvils exhibited a high degree of aggregation of these frozen droplets and higher levels of NO_x. In contrast, a deep convective cell with low lightning flash rates had high concentrations of both frozen droplets and aggregated frozen droplets in its anvil's central region. A conceptual model for these results is presented and applied to the observations from each of these storms. High NO_x concentrations are often found where aggregation of frozen droplets has occurred, which may be a reflection of aggregation by electrical forces in the regions where lightning is occurring, although the level of NO_x for a given concentration of aggregates varies from storm to storm. These observations between anvil microphysics and lightning and/or NO_x signatures suggest that lightning data may be an important tool to characterize or infer the microphysical, radiative, and chemical properties of thunderstorm anvils.