Estimates of cloud charge densities in thunderstorms

Abstract

The total charge density and the precipitation charge density inferred from six balloon soundings of electric field and precipitation charge are compared in order to examine the distribution of cloud charge density in small New Mexican mountain thunderstorms. Cloud charge density magnitudes were typically less than 2.0 nC m−3, and the maximum cloud charge densities were −2.1 and +6.7 nC m−3. The cloud charge density made a significant contribution to the total charge density in most of the thunderstorm depth, especially in the upper positive and upper negative charge regions, where all the charge was typically on cloud particles. The largest positive cloud charge densities were found just above the main negative charge region. In the lower part of the main negative charge region, the cloud charge density was the major contributor to the total charge density, and the precipitation charge played a minor role. The cloud charge density was often zero in lower positive charge regions but was 20–50% of the total charge density in two cases. Between the upper positive charge region and the bottom of the main negative charge region the cloud charge density changes polarity and tends to become increasingly negative with decreasing altitude.