Electrification life cycle of incipient thunderstorms

Abstract

This work evaluates how clouds evolve to thunderstorms in terms of microphysical characteristics to produce the first intracloud (IC) and cloud‐to‐ground (CG) lightning flashes. Observations of 46 compact isolated thunderstorms during the 2011/2012 spring‐summer in Southeast Brazil with an X‐band polarimetric radar and two‐ and three‐dimensional Lightning Location Systems demonstrated key parameters in a cloud's vertical structure that produce the initial electrification and lightning activity. The majority (98%) of the first CG flashes were preceded (by approximately 6 min) by intracloud (IC) lightning. The most important aspect of the observations going into this paper, which came originally from the visual examination of a large number of thunderstorms, is that an initial positive differential reflectivity (ZDR) (associated with supercooled raindrops) evolved to reduced ZDR (and even negative values) in the cloud layer between 0° and to −15°C before and during the time of the initial lightning, suggesting evolution from supercooled raindrops to frozen particles promoting the formation of conical graupel. An enhanced negative specific differential phase (KDP) (down to −0.5° km−1) in the glaciated layer (above −40°C) was predominantly observed at the time of the first CG flash, indicating that ice crystals, such as plates and columns, were being vertically aligned by a strong electric field. These results demonstrate that the observations of ZDR evolution in the mixed layer and negative KDP in the upper levels of convective cores may provide useful information on thunderstorm vigor and lightning nowcasting.

Determining Electric Fields in Thunderclouds With the Radiotelescope LOFAR

“…It is known that cloud electrification occurs in regions with large updrafts and when there is a sufficient amount of precipitation particles present (e.g., MacGorman & Rust, ). This means that conditions required for charge separation (Mattos et al, ) have specific signatures in radar data, with high low‐level reflectivity values (e.g., Dixon & Wiener, ), and high echo tops (e.g., Ushio et al, ). Radar reflectivity at 1,500 m altitude and the maximum height at which radar reflectivity is at least 7 dBZ (i.e., echo top heights) derived from the operational weather radar network of the Netherlands is used here to study whether the conditions for cloud electrification are met.…”

Concurrent satellite and ground-based lightning observations from the Optical Lightning Imaging Sensor (ISS-LIS), the low-frequency network Meteorage and the SAETTA Lightning Mapping Array (LMA) in the northwestern Mediterranean region

“…Graupel and small hail ice mass correlate especially well with the mean total lightning rate in their study. Among others, Mattos et al (2017) investigated the life cycle of thunderstorms and processes leading to the different discharge types. They found in their analysis of 46 isolated thunderstorms that in 98 % of their cases, the first CG flash is preceded by IC lightning by approximately 6 min on average.…”

Overview: Precipitation characteristics and sensitivities to environmental conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

“…Figure 6 shows the CFAD for the dual-polarization parameters, ZDR, KDP, and co-polar correlation coefficient. The hydrometeor response to the transmitted signal depends on several factors that may alter certain characteristics of the measured signal, such as hydrometeor orientation by the electrification field (see Mattos et al, 2017, for a detailed discussion), ice density, and crystal shape. Of course, there are also other possible effects that may impact the data quality, such as resonance and partial beam-filling.…”