Fog Interception of Four Southern Appalachian Mountain Sites

Smathers, Garrett

ABSTRACT: Fog interception, which consisted of moisture from wind-driven rain clouds and clouds forming at or moving across high elevations during rainless periods, was determined for four southern Appalachian summit areas ranging in elevation from 1,610 m to 1,855 m. Gauge stations were established in mixed hardwood-spruce-fir forests, a spruce-fir forest, and a heath bald. Fog yield (mm) was determined as difference in precipitation received by paired Hellmann rain gauges, one fitted with a Grunow fog interceptor. Fog yield was computed as percentage gain over precipitation received in gauge without fog interceptor. During relatively normal precipitation, percentage gains were 51% in mixed hardwood-spruce, 94% in spruce-fir, and 93% in heath bald. During well below normal precipitation, gains were from 38% in mixed hardwood-spruce-fir; 86% in spruce-fir; they dropped precipitously to 42% in the heath bald. Maximum gains in this study are among the highest reported for similar studies of cloud forests in the United States and Mexico. Quantity and seasonal distribution of fog yield in the different vegetation types suggest that fog interception may be an important factor in determining vegetation patterns in the spruce-fir zone.