Highway 120 Corridor Weather Station Installations And Upgrades

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The purpose of this project is to upgrade 7 existing PERMANENT weather stations and install 5 new PERMANENT stations along the Highway 120 corridor in Yosemite National Park. In addition, each site would be seasonally instrumented with up to 20 TEMPORARY snow depth sensors to characterize the variability in snow depth at each site. Proposed locations may be adjusted to avoid impacts to cultural resources (review pending).

All new and upgraded weather stations lie within non-Wilderness along the Highway 120 road corridor. These instrument installations should be considered permanent installations. Five new weather stations would be installed at 1) 1.5 miles south of Big Oak Flat Entrance Station, 2) near the entrance to the road to the Rockefeller Grove, 3) At Smoky Jack Creek, 4) Near Olmstead Pit (preferred) or Hoffman Creek, and 5) Near Gaylor Pit or Gaylor Creek. The latter would replace an existing fire Remote Access Weather Station (RAWS) presently located in designated Wilderness. Upgraded stations would be 1) Crane Flat Lookout RAWS, 2) Dog House Meadow, 3) Gin Flat, 4) White Wolf RAWS, 5) Porcupine, 6) Tenaya Lake and 7) Tuolumne Meadows. See Location and Site figures.

New stations would consist of a 20 foot tall 3-inch in diameter galvanized metal mast pole set in concrete footer approximately 4 feet deep and 18 inches in diameter (see figure). Attached to the pole would be two temperature and humidity sensors, radiometer, snow depth sensor, rain gauge, fuel moisture sensor, barometer, datalogger and battery pack, a solar panel, and satellite antenna for transmitting the data in near real-time. Associated with each station would be two soil temperature and moisture arrays, one next to the tower described above and one within 200 yards, and up to 6 dendrometer bands to measure tree growth. Installation of each soil temperature/moisture array would require the excavation of an 18 inch diameter hole up to 4 feet deep. Sensor wiring from each array would be placed in 1-inch PVC conduit extending from the instruments to the weather tower. Conduit would be buried in a trench 4-6 inches wide, 6-10 inches deep, and up to 200 meters from the weather tower.Dendrometer bands would be placed around selected trees and transmit information wirelessly to the weather tower. See instrumentation figures.

Upgrades for the seven existing stations would be the installation of two soil moisture / temperature arrays, up to six dendrometer bands, and one fuel moisture sensor per site as described above. Crane Flat Lookout RAWS, would require the excavation of a footer for a new tower. The existing tripod structure has no foundation.

Each of the above sites would be instrumented seasonally with up to 20 snow depth sensors for a period of up to 10 years. These sensors would be mounted on T-posts driven into the ground and stand 10-15 feet in height (see photo). Most of these instruments would be removed following the end of snow melt each season to reduce their visual impact. Some would be left in place to reduce the burden of reinstalling all the instruments each season. These instruments would be put in place seasonally for up to ten years from 2006.

Stations would be maintained by California Cooperative Snow Surveys, National Interagency Fire Center (NIFC) personnel (for the RAWS network), and a consortium of researchers from the U.S. Geological Survey, Scripps Institute of Oceanography, and the University of California Merced. Many stations would broadcast data via satellite and the information made available in near real-time on the internet. Non-real-time data would be made available to the National Park Service (NPS) and the public.