A new automated method to retrieve charge layer polarity from flashes, named Chargepol, is presented in this paper. Using data from the NASA Lightning Mapping Array (LMA) deployed during the RELAMPAGO field campaign in Cordoba, Argentina, from November 2018 to April 2019, this method estimates the polarity of vertical charge distributions and their altitudes and thicknesses (or vertical depth) using the very-high frequency (VHF) source emissions detected by LMAs. When this method is applied to LMA data for extended periods of time, it is capable of inferring a storm’s bulk electrical charge structure throughout its life cycle. This method reliably predicted the polarity of charge within which lightning flashes propagated and was validated in comparison to methods that require manual assignment of polarities via visual inspection of VHF lightning sources. Examples of normal and anomalous charge structures retrieved using Chargepol for storms in Central Argentina during RELAMPAGO are presented for the first time. Application of Chargepol to five months of LMA data in Central Argentina and several locations in the United States allowed for the characterization of the charge structure in these regions and for a reliable comparison using the same methodology. About 13.3% of Cordoba thunderstorms were defined by an anomalous charge structure, slightly higher than in Oklahoma (12.5%) and West Texas (11.1%), higher than Alabama (7.3%), and considerably lower than in Colorado (82.6%). Some of the Cordoba anomalous thunderstorms presented enhanced low-level positive charge, a feature rarely if ever observed in Colorado thunderstorms.

Thunderstorms exhibiting anomalous charge structures (ACSs, i.e., anomalous storms) are comprised by more riming ice carrying net positive versus negative charge, thought to result from increased mixed-phase cloud liquid water content (LWC). Anomalous storms are rarely observed in the United States (US) outside of the Great Plains (GP) region, where environmental conditions that suppress warm precipitation efficiency and support robust updrafts are thought to favor increased mixed-phase LWC. Two rare anomalous supercells in the Southeastern (SE) US exhibited similar charge structure characteristics as observed in GP anomalous storms, including a deep positive (negative) charge layer associated with riming (non-riming) ice in the lower (upper) mixed-phase region. However, most characteristics associated with SE anomalous environments were not consistent with those in the GP. A more rigorous evaluation of hypotheses concerning ACS development and their observation in the SE compared electrical, kinematic, microphysical, and environmental properties between the two anomalous and two SE normal supercells (i.e., exhibiting normal charge structures). Similar metrics of warm precipitation efficiency were observed in each. However, lower relative humidity in the charging region of the SE anomalous storms uniquely matched environmental characteristics in GP anomalous storms and differentiated SE anomalous from normal environments, suggesting the relative importance of saturation ratio alongside LWC in positive charging of riming ice. Differences were also observed in charge region characteristics and flash locations between a SE anomalous and normal storm. As riming ice increased in the negative charge region of the ACS, flash initiation locations were increasingly observed in stronger updrafts and updraft gradients compared with the normal storm. The evolution of microphysical characteristics of the negative charge region in the anomalous storm suggested an increase in normal alongside anomalous charging, indicating that variability in charging polarity may impact spatial flash relationships with the updraft. Further work is needed to diagnose whether particle-scale charging variability influences flash rate relationships with convective parameters such as updraft or graupel volume.

The development of mobile profiling facilities at the University of Alabama in Huntsville has led to the formation of the Mobile Atmospheric Profiling Network (MAPNet), which is now available to the broader scientific community as part of the NSF supported Community Instruments and Facilities (CIF). The MAPNet consists of the following four mobile platforms (commercially available instruments are defined within parentheses): MIPS – Mobile Integrated Profiling System (915 MHz Doppler wind profiler, X-band Profiling Radar, Microwave Profiling Radiometer, lidar ceilometer); RaDAPS – Rapidly Deployable Atmospheric Profiling System (915 MHz Doppler wind profiler, Micro-Rain Radar, Microwave Profiling Radiometer, and lidar ceilometer); MoDLS – Mobile Doppler Lidar and Sounding System (Doppler wind lidar, Microwave Profiling Radiometer); and MAX – Mobile Alabama X-band scanning dual polarization radar. All four systems include near-surface in situ measurements of state variables and balloon sounding capabilities. This presentation will review the measurement capabilities of each instrument, and the research capabilities of the MAPNet. A unique concept of this suite of platforms is the combination of sensors that can provide high temporal-resolution (<5 min) profiles of wind, temperature, humidity, aerosols, cloud base, and precipitation over a broad range of conditions. Therefore, both boundary layer and precipitation research can be supported. Examples of measurements will include the following: Utilization of the MAPNet in a network mode to document the spatiotemporal variability of boundary layer and associated stratocumulus clouds preceding cool season, severe quasi-linear systems; Comparisons of wind profiles and vertical motion among the individual instruments; Measurements of bores and gust fronts within the planetary boundary layer; Integration of data from disparate profiling systems to promote understanding of complex boundary layer evolution within precipitation, including landfalling hurricanes; Examples of educational deployments that have utilized the MAPNet in the past, and may serve as a prototype for educational deployments in the future.