Anvil microphysical signatures associated with lightning-produced NO<sub><i>x</i></sub>

Abstract

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.

Electrification in Mesoscale Updrafts of Deep Stratiform and Anvil Clouds in Florida

“…The laboratory studies of Saunders and Wahab (1975) and Wahab (1974) showed that in a vertical electric field (i.e., the field was aligned with the direction of fall) a threshold of ice crystal concentration of 250/L and an electric field threshold of~60 kV/m was required in order to enhance aggregation. In another study Stith et al (2016) have observed chain-like aggregation of frozen cloud droplets in the upper parts of some anvils in association with high values of NO x in which lightning was known to have occurred. They attributed the aggregation of frozen droplets to electric field forces.…”

Introduction to the Deep Convective Clouds and Chemistry (DC3) 2012 Studies

“…Journal of Geophysical Research: Atmospheres 2.7. Cloud Structure Analyses of cloud physical properties were conducted using aircraft measurements of cloud particle size distributions (Stith et al, 2016) and water vapor (Diao et al, 2017), as well as balloon-borne video disdrometer (Waugh et al, 2018). The recently developed balloon-borne microphysics probe can provide observations at fine scales and give calculated cloud particle mixing ratios and reflectivity in agreement with radar and cloud-resolving, kinematic model results.…”

“…The frozen drop aggregates are formed by electrical forces associated with high electric fields accompanying lightning. Since lightning is also the source of lightning-NO x , these studies suggested that electrically active storms may have characteristically different ice particle types in the anvil compared to less electrically active storms, which may have an impact on the radiative impacts of the anvil clouds (Stith et al, 2016).…”

Why Flash Type Matters: A Statistical Analysis

“…There is a renewed interest in how lightning characteristics influence NO x and other chemical species, including recent studies emanating from the Deep Convective Cloud and Chemistry (DC3) experiment (e.g., Barth et al, 2015;Carey et al, 2016;DiGangi et al, 2016;Mecikalski et al, 2015;Mecikalski & Carey, 2017;Pollack et al, 2016;Stith et al, 2016). However, as mentioned, only Mecikalski and Carey (2017) separately classified hybrid flashes from CG flashes in their study.…”