The Electrical Characteristics of Some Severe Hailstorms in Alberta, Canada

Abstract

While the role of gravitational, thermodynamic and hydrodynamic forces in thunderstorms has been extensively studied, that of electrical processes is still little understood. Measurements of the electric fields beneath storms were conducted during the summers of 1968 to 1970. Electrostatic voltmeters (field mills) were constructed and used in Alberta both in fixed station operation and in mobile operation. Aided with information from radar, hailfall and rainfall, case studies of three storms were performed. The analysis of the results suggested that the dynamical features of storms play a more important part than the microphysical ones in affecting the electrical behaviour of storms, once the conditions necessary for the charging mechanism to function are satisfied. In particular, for storms penetrating into the stratosphere, the organization of the storms becomes extremely important and the amount of lightning manifested by a storm complex is directly related to the number of cells within the complex. Two conclusions on the properties of the charging mechanism were also realized, viz. (i) the efficacy of the charging mechanism is not increased by increasing the updraft speed, and (ii) the charging mechanism should produce lightning of frequency 1-3 flashes per minute for each storm cell, irrespective of whether the storm is a thunderstorm, hailstorm or severe storm.