Installation of automated weather station near Vogelsang High Sierra Camp
This project will install an automated snow pillow and weather station within the footprint of the Vogelsang High Sierra Camp. The installation will consist of a snow pillow, a 25-foot tall Rohn tower, a 20-foot tall storage precipitation gage and sensors measuring net radiation, incoming solar radiation, air temperature, relative humidity, barometric pressure, wind speed, wind direction, snow depth, soil moisture and temperature at three depths ranging from ~5-25cm, and a tipping bucket. The installation would be powered by a solar panel and rechargeable battery, and data would be stored and collected by a data logger located in a weatherproof enclosure and transmitted via a GOES (Geostationary Operational Environmental Satellite) transmitter. A geotechnical investigation would occur prior to work to determine the suitability of granite bedrock in the project areas to act as the foundation for the Rohn tower.
The geotechnical investigation would likely consist of hand digging utilizing a small pick and shovel to estimate the soil cover where the soil cover is thin (less than 12 inches). Excavations would not exceed 4 square feet in area and would be backfilled upon completion of excavation. It is anticipated that estimation of the rock properties would be performed using a field rock hammer (hand held geologist hammer) coupled with detailed mapping of discontinuities, including fractures, cracking, contact between rock units and planes of weakness, and weathered zones, and other types of dissimilar materials that provide information regarding weathering, rock hardness, strength, and rock quality. Disturbance will be limited to indentations by the manual rock hammer and scoffing of the rock surface, and possible splaying of rock surfaces where weak rock is broken from the rock mass. Exploration will not include coring, mechanical drilling, or such disturbance. Any disturbed surface will be limit of a few inches of broken surficial rock in isolated locations, typically less than 1 foot by 1foot.
Justification: Thirteen remote weather stations in Yosemite National Park provide hourly real time data that is used to inform a variety of park operations related to visitor safety, road openings, wildfire management, and to monitor extreme weather events such as winter storms, floods, and drought. Weather station data is also used to understand and track changes in the park ecosystem, such as the impacts of warming temperatures on forests, meadows, and wildlife populations. Park staff, Department of Water Resources, and the National Weather Service also use these data to forecast and monitor flooding during spring-snowmelt runoff, and snowline elevation during major winter storms.
In 1979 the Yosemite Superintendent signed a memo allowing 10 snow pillows in the park. The 1989 Yosemite Wilderness Management Plan allowed for the continuation of existing meteorological installations but prohibited new installations except those proposed and approved in 1979. The last undeveloped site in wilderness referenced by these documents is Moraine Meadows at 8700 feet. This site was never installed; at this time we propose to install the remaining automated snow sensor site within proposed wilderness at Vogelsang High Sierra Camp at 10,100 feet. This site will better represent the higher elevations of the Merced watershed; currently the highest elevation station in the Merced is 8,199 feet.
The components of the system consist of the following:
1 - Snow pillow composed of 4 stainless steel pads containing a solution of propylene glycol-ethanol covering an area of approximately 8 feet x 10 feet. The pillow will be plumbed to measure pressure with a pressure transducer.
2 - 25-foot tall Rohn tower with base bolted to an existing granite slab. Tower is a maximum distance of two feet from the edge of the snow pillow. Tower supports meteorological instrumentation as well as the solar panel, satellite transmitter, and datalogger.
3 - Installation of a 20-foot tall storage precipitation gage adjacent to the Rohn tower. Base rests on railroad ties.
4 - Three soil moisture sensor installed to a depth of 30 centimeters.
5 - Lightning ground buried horizontally or at an angle into the ground surface.
The geotechnical investigation will occur before the installation commences. The two activities may not occur in the same year. It is anticipated that installation of this equipment would require helicopter flights to bring in the snow pillow, tower sections, and storage precipitation gage. No more than three helicopter flights are allowed per the MRA. Mule teams could bring in additional equipment.