HR: 0800h
AN: B11A-1008    [Abstracts]
TI: A New Passive Fog Collector Design for Measuring Fog Water Inputs and Isotopic Composition in Harsh and Remote Environments
AU: * Fischer, D T
EM: fischer@geog.ucsb.edu
AF: University of California at Santa Barbara, Department of Geography 3611 Ellison Hall, Santa Barbara, CA 93106 United States
AU: Still, C J
EM: still@icess.ucsb.edu
AF: University of California at Santa Barbara, Department of Geography 3611 Ellison Hall, Santa Barbara, CA 93106 United States
AB: We present a new design for a passive fog collector that has proven useful both for collecting fog quantity information, and for collecting samples for isotopic analysis. The new collector is more sensitive to short-duration and low-intensity fog events than other designs we examined. This collector was developed as part of a larger study of the role that fog and persistent stratus clouds play in ecological processes in the California Channel Islands. Our work is primarily focused on a population of Bishop Pines (Pinus muricata) on Santa Cruz Island. The study area is subject to frequent short-duration, low-intensity fog events, with peak occurrence during the rainless summer months. Fog water inputs are sufficient to wet the soil down below 25cm when surrounding soils are quite dry (water potentials less than -1.5MPa). Pines appear to be quite effective at harvesting fog drip from fog events that did not register on a prototype mesh collector. Harp-style collectors, that use only vertically-oriented strands for collection, generally respond more quickly to the beginning of fog events than do mesh collectors. However, existing harp collectors were judged too expensive to buy, and too complex to build and maintain to deploy in large numbers. The new harp-style collector was designed for efficient fog collection during short-duration, low-intensity fog events, while being inexpensive, durable, and easy to construct. The new design has reduced rain-water contamination compared to other designs examined. The reduced storage of fog water on the collection surface (compared to a mesh collector) also minimizes the risk of isotopic enrichment of samples during prolonged, intermittent fog events. Real-time comparisons with an active fog collector suggest minimal isotope fractionation. Nineteen fog collectors installed at eleven sites throughout the main stand have provided spatially distributed estimates of fog-water inputs to the ecosystem. Samples of fog-water from collectors have been analyzed monthly for stable isotope content as part of the larger study. Large differences in isotopic composition between fog and rain waters are used to partition ecosystem use of their hydrologic inputs. Additional collectors are being installed for companion studies on the California mainland coast (Cambria), and in tropical montane cloud forest sites (Monteverde, Costa Rica).
DE: 0320 Cloud physics and chemistry
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0452 Instruments and techniques
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1840 Hydrometeorology
SC: Biogeosciences [B]
MN: Fall Meeting 2005