Electrification and lightning are simulated for a small continental multicell storm. The results are consistent with observations and thus provide additional understanding of the charging processes and evolution of this storm. The first six observed lightning flashes, all negative cloud-to-ground (CG) flashes, indicated at least an inverted dipole charge structure (negative charge above positive). Negative CG flashes should be energetically favorable only when the negative charge region contains appreciably more charge than the lower positive region. The simulations support the hypothesis that the negative charge is enhanced by noninductive charge separation higher in the storm that also causes development of an upper positive charge region, resulting in a "bottom-heavy" tripole charge structure. The two-moment microphysics scheme used for this study can predict mass mixing ratio and number concentration of cloud droplets, rain, ice crystals, snow, graupel, and hail. (Hail was not needed for the present study.) Essential details of the scheme are presented. Bulk particle density of graupel and hail can also be predicted, which increases diversity in fall speeds. The prediction of hydrometeor number concentration is critical for effective charge separation at higher temperatures (−5 < T < −15) in the mixed-phase region, where ice crystals are produced by rime fracturing (Hallett-Mossop process) and by splintering of freezing drops.

A database consisting of approximately 4000 storm observations has been objectively analyzed to determine environmental characteristics that produce high radar reflectivities above the freezing level, large total lightning flash rates on the order of 10 flashes per minute, and anomalous vertical charge structures (most notably, dominant midlevel positive charge). The storm database is drawn from four regions of the United States featuring distinct environments, each with coinciding Lightning Mapping Array (LMA) network data. LMAs are able to infer total lightning flash rates using flash clustering algorithms, such as the one implemented in this study. Results show that anomalous charge structures inferred from LMA data, significant lightning flash rates, and increased radar reflectivities above the freezing level tend to be associated with environments that have high cloud base heights (approximately 3 km above ground level) and large atmospheric instability, quantified by normalized convective available potential energy (NCAPE) near 0.2 m s −2 . Additionally, we infer that aerosols may affect storm intensity. Maximum flash rates were observed in storms with attributed aerosol concentrations near 1000 cm −3 , while total flash rates decrease when aerosol concentrations exceed 1500 cm −3 , consistent with previous studies. However, this effect is more pronounced in regions where the NCAPE and cloud base height are low. The dearth of storms with estimated aerosol concentrations less than 700 cm −3 (approximately 1% of total sample) does not provide a complete depiction of aerosol invigoration.

DC3 brought together simultaneous measurements of storm kinematics, structure, electrical activity, and chemistry to improve our knowledge of how thunderstorms affect the chemical composition of the troposphere.

Previous analyses of very high frequency (VHF) Lightning Mapping Array (LMA) observations relative to the location of deep convective updrafts have noted a systematic pattern in flash characteristics. In and near strong updrafts, flashes tend to be smaller and more frequent, while flashes far from strong vertical drafts exhibit the opposite tendency. This study quantitatively tests these past anecdotal observations using LMA data for two supercell storms that occurred in Oklahoma in 2004. The data support a prediction from electrostatics that frequent breakdown and large flash extents are opposed. An energetic scaling that combines flash rate and flash area exhibits a 5 /3 power-law scaling regime on scales of a few kilometers and a maximum in flash energy at about 10 km. The spectral shape is surprisingly consistent across a range of moderate to large flash rates. The shape of this lightning flash energy spectrum is similar to that expected of turbulent kinetic energy spectra in thunderstorms. In line with the hypothesized role of convective motions as the generator of thunderstorm electrical energy, the correspondence between kinematic and electrical energy spectra suggests that advection of charge-bearing precipitation by the storm's flow, including in turbulent eddies, couples the electrical and kinematic properties of a thunderstorm.

[1] The temporal and spatial development of sprite-producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system (MCS) on 29 June 2011 near the Oklahoma Lightning Mapping Array (LMA). Sprites produced by a total of 26 lightning flashes were observed simultaneously on video from Bennett, Colorado and Hawley, Texas, enabling a triangulation of sprites in comparison with temporal development of parent lightning (in particular, negatively charged stepped leaders) in three-dimensional space. In general, prompt sprites produced within 20 ms after the causative stroke are less horizontally displaced (typically <30 km) from the ground stroke than delayed sprites, which usually occur over 40 ms after the stroke with significant lateral offsets (>30 km). However, both prompt and delayed sprites are usually centered within 30 km of the geometric center of relevant LMA sources (with affinity to negative stepped leaders) during the prior 100 ms interval. Multiple sprites appearing as dancing/jumping events associated with a single lightning flash could be produced either by distinct strokes of the flash, by a single stroke through a series of current surges superposed on an intense continuing current, or by both. Our observations imply that sprites elongated in one direction are sometimes linked to in-cloud leader structure with the same elongation, and sprites that were more symmetric were produced above the progression of multiple negative leaders. This suggests that the large-scale structure of sprites could be affected by the in-cloud geometry of positive charge removal. Based on an expanded dataset of 39 sprite-parent flashes by including more sprites recorded by one single camera over the same MCS, the altitude (above mean sea level, MSL) of positively charged cloud region tapped by sprite-producing strokes declined gradually from~10 km MSL (À35 C) to around 6 km MSL (À10 C) as the MCS evolved through the mature stage. On average, the positive charge removal by causative strokes of sprites observed on 29 June is centered at 3.6 km above the freezing level or at 7.9 km above ground level.

The Geostationary Lightning Mapper (GLM) continuously observes lightning throughout a near‐hemispheric field of view, capturing spatiotemporal variability on unprecedented scales. This study documents GLM lightning distributions during the initial 9 months in the operational Geostationary Operational Environmental Satellite‐East position (December 2017 to August 2018). Spatial maps, summary statistics, and time series illustrate seasonal, regional, and diurnal lightning patterns. Lightning activity shifts from south to north during the study period with most lightning over land (83%). The average GLM flash extends over a 454‐km2 area, lasts 301 ms, produces 262 fJ of optical energy, and consists of 16.4 (42.2) groups (events). On average, GLM flashes over the oceans are larger (570 km2), of longer duration (345 ms), and brighter (420 fJ) than flashes over land (431 km2, 293 ms, and 230 fJ). The baseline values and early insights reported herein aim to guide the early development and application of GLM observations.

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