Abstract
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 Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (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.
Highlights
Past studies have associated the severity of thunderstorms with patterns in charge distribution (Fuchs et al, 2018; Wiens et al, 2005)
Using data from the NASA Lightning Mapping Array (LMA) deployed during the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (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 using the very-high frequency (VHF) source emissions detected by LMAs
This paper presented charge structures for the warm season thunderstorms in Cordoba, Argentina for the first time through thunderstorm examples and long-term statistics utilizing a new method that identifies charge layer polarity at a flash level from LMA VHF data
Summary
Past studies have associated the severity of thunderstorms with patterns in charge distribution (Fuchs et al, 2018; Wiens et al, 2005). Due to the nature of lightning processes and their characteristic emission in the very-high frequency (VHF) spectrum, thunderstorm charge structures associated with flashes can be inferred from Lightning Mapping Array (LMA) observations (Lang & Rutledge, 2011; Rust et al, 2005; Wiens et al, 2005). Mapping of VHF sources is used to manually determine the location of positive and negative charge layers (Bruning et al, 2007; Lang and Rutledge, 2008; Rust et al, 2005; Wiens et al, 2005). An intra-cloud lightning (IC) flash initiates in a region with strong electric field, in between regions of charge with opposite polarities.
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