Disturbed weather measurements in atmospheric electricity using an instrumented van

Abstract

Precipitation currents have been measured using an exposed receiver. Compensation for field currents has been achieved by subtracting the field currents to a probe, suitably amplified, from the total current to the exposed receiver. The potential gradient has been measured using a field mill, the theory of which has been rederived. Wind speed was also measured with a contact cup anemometer. The apparatus was installed in a Land Hover thus providing a mobile observatory. The results obtained led to an analysis of the conditions in quiet rain when the inverse relation is not evident. The slope of the regression line between current and potential gradient is shown to depend upon the phase angle of the lag between the current-time and potential and potential gradient-time records. A method for deducing the lag or lead in records when the mirror image effect is not apparent has been evolved from consideration of the Lissajous plots first described by RAMSAY (1960). The method has been used to show some support for the ideas of CHAIMERS (1305) concerning the behaviour of records taken beneath approaching and developing cloud systems. Both the approaching and developing situations have been observed. An experiment has been described which conclusively shows the pylon to be the source of negative apace charge associated with power lines in mist or fog. An explanation is offered in terms of the different mobilities of free electrons and positive ions which are supposed to be formed byionisation due to tracking; across the damp insulators. The electrons are shown during the negative phase of the line voltage to travel a distance before their capture which is greater than that from which they can be drawn back when the polarity of the alternating voltage changes. Measurements of polar conductivities at two levels, above and below the 0ºC isotherm, have been made during steady snowfall with a Gerdien conductivity chamber. From these measurements the charge separation rate in the melting region has been estimated.