Atmospheric Electricity and the Waterfalls of Yosemite Valley

Abstract

Measurements of the electric field on the floor of Yosemite Valley show that the field is usually small in size and negative in sign. As individual waterfalls are approached the field can become several hundreds of volts per meter negative. Traverses up the steep sides of the valley showed a steady trend to increasingly positive fields with increasing height; on the plateau above the valley the field was of the order of +100 v m?1, a conventional fair weather value. Characteristic diurnal variations in field were noted at the valley floor. A maximum of about +10 v m?1 was reached near local noon with a minimum of some ?60 v m?1 at midnight. The field fluctuated violently at night, but the variations were slow by day. The results can be interpreted in terms of a convective exchange layer the development of which is in phase with solar heating, with negative space charge produced at the waterfalls being entrained into the exchange layer.