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Initial electrification to the first lightning flash in New Mexico thunderstorms
Author(s) -
Stolzenburg Maribeth,
Marshall Thomas C.,
Krehbiel Paul R.
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd023988
Subject(s) - thunderstorm , flash (photography) , storm , meteorology , radar , electric field , environmental science , atmospheric sciences , physics , geology , astrophysics , optics , telecommunications , quantum mechanics , computer science
Abstract The initial electrification of three New Mexico thunderstorms is examined using in situ and remote measurements. The earliest deflection of electric field ( E ) measured at the surface was 5–8.6 min before the first flash and coincident with the development of substantial radar reflectivity (40 dBZ) above −5°C. Rapid growth of surface E (>5 V/m/s) started 2.4–3.1 min before the first flash, when 40 dBZ reflectivities reached above the −15°C level. In two cases with clear surface E records, radar reflectivity indicators (40 dBZ echo through −10°C and echo top through −15°C) would yield longer warning times before the first flash than the E record. The first flash in each storm initiated at altitudes between 7.4 and 8.8 km; hence, the temperatures where the largest (negative) E for normal intracloud lightning initiation had developed during the initial electrification were −10°C to −20°C. Negative and positive charge regions associated with the first flash in each cell were centered at −8°C to −16°C (6.9–8.0 km) and −20°C to −24°C (9.0–9.2 km), respectively. In two cases, balloon data indicate the only substantial charge regions present before the first flash were those involved in the flash. Another case shows an initial period of opposite polarity E deflection at the surface coincident with substantial low‐level positive charge within the cloud, although this charge was not involved in the first 8 min (first 17 flashes) of lightning activity. The findings support the notion that the initial electrification resulted from charging via the noninductive ice‐ice collisional mechanism.