A Study of the Variability of Thunderstorm Electrical Events Based on Very-Low-Frequency Electromagnetic Data

摘要

Sferics counts were used to estimate the incidence of lightning discharges; study the relationship of lightning-flash density to thunderstorm days; and explore the variability to cloud-to-ground discharges. Areal and global discharge incidence estimates were generated from sferics, yielding a global estimate of 1.3 times ten to the minus 5th power /Sq km/s. Gridded monthly values are given for much of the Eastern Hemisphere. The Southern Hemisphere tropics were found to have a average incidence of discharge than the Northern Hemisphere tropics. The linear regression relationship between flash density and thunder storm days indicated lower estimates of flash density when based on data stratifications compared to previous studies. Selected data from the Eastern Hemisphere were studied by linear regression techniques for causes of large-scale variability of cloud-to-ground discharges. In order of importance the regressors were the height of freezing level, the planetary geomagnetic index, a parameterization of the height of the freezing level, precipitable water in 1000-850 mb layer, the dew-point depression at 850 mb, the K index of stability, and the departure of the H-component of the magnetic force vector from its mean. (Author)