Observations of the electric field in the stratosphere over an arctic storm system

Abstract

Observations by balloon‐borne instrumentation in the stratosphere (30–35 km) near Sondre Stromfjord, Greenland, have revealed disturbed vertical electric fields of the order of volts per meter of both polarities above an arctic storm system which moved onto the continent from the Davis Strait on August 11, 1982. This disturbance persisted at the balloon position for more than 10 hours, exhibiting order of magnitude variations with time scales ranging from minutes to hours. Simultaneous measurements of the stratospheric electrical conductivity did not show significant storm‐related variations. No lightning signals were detected, either at the balloon or at meteorological stations in the Davis Strait area. The disturbed field was predominantly downward (normal fair‐weather direction), and estimates of the total current indicate that at any instant a current of the order of 0.5 A was communicated to the storm system via the overlying stratosphere. The responsible storm system has been uniquely identified by NOAA 7 satellite IR (10.5–11.5 μm) imagery, and the infrared measurement of cloud‐top temperatures has revealed zones of enhanced convection lying in the storm's interior. Meteorological measurements taken at the surface and from balloon radiosondes by stations in the path of the storm also suggest that the storm possessed convective instabilities of the type likely to produce cloud electrification. In tropospheric features this type of storm occurs rather frequently on the western Greenland coast; therefore electrical charging of the storm cloud systems may not be as rare as indicated in the low probabilities observed for thunder and lightning.