Charged precipitation and electric field in two thunderstorms

Abstract

The net electric charge density on all particles inside a thunderstorm can be estimated from measurements of the electric vector along a mainly vertical path of a balloon‐borne sensor. In addition, the net charge density on precipitation particles such as raindrops, hail, and graupel can be deduced from measurements of the charge on each individual particle. This paper reports on two balloon soundings of electric field and precipitation charge in two different storms in central New Mexico. The two soundings are similar at lower heights and different at higher heights, possibly because one balloon ascended outside the main convective updraft core of the storm, while the other balloon ascended within the updraft. Six charge regions were inferred from the sounding outside the updraft core in the convective region. In the lowest four charge regions, including the lower positive, main negative, and two oppositely charged regions in between, the detected precipitation charge density (on particles with individual charges of at least 10 pC) was of the same polarity and as large or larger in magnitude than the total charge density. At the top of and 0.4 km above the main negative charge region a large number density (about 125 m−3) of negatively charged precipitation particles were detected; these particles had larger mean charge (−48.6 pC) than any other group of positive or negative particles detected elsewhere in the sounding. The second electric field sounding was typical of updraft soundings below 8.0 km, and the precipitation particles detected were all positively charged below 5.3 km and all negatively charged above. The detected precipitation charge density, although smaller in magnitude, was of the same polarity as the total charge density in the lower positive and main negative charge regions.