In 2009/2010 a new feature was installed on the Sunset trail at the Skyway Ski Trails – a 30 foot tall tower equipped with weather, snowpack and radiation sensors that are continuously collecting wind speed and direction, air temperature, relative humidity, snowpack depth, and a variety of incoming and reflected solar radiation data, all solar powered.
Referred to as the Grand Mesa Study Plot, this installation is a collaborative project of the Colorado Dust-on-Snow (CODOS) program based at the Center for Snow and Avalanche Studies in Silverton, the University of Utah’s Snow Optics Laboratory, and the US Geologic Survey’s Southwest Biological Science Center in Moab, who funded the installation. The GMSP adds an important new site monitoring changes in snowpack reflectance (albedo) and solar energy absorption caused by desert dust deposition to the CODOS program’s identical set of measurements made in the San Juan Mountains. This automated monitoring, combined with occasional snowpack profiles at the site, will enhance CODOS’s ability to advise western Colorado water managers about potential dust-in-snow effects on snowmelt timing and rates.
Data from these Grand Mesa Study Plot instruments is also being used by the Colorado Avalanche Information Center (CAIC) avalanche forecaster responsible for Highway 65 as well as by the National Weather Service forecasters in Grand Junction. Representatives of the Grand Mesa Nordic Council, the National Weather Service, and CAIC offered their endorsement of the GMSP during a site inspection with Grand Valley Ranger District staff and the CSAS in June 2009. Given the multiple applications of the data for research, water management, public safety, and other public purposes, the Grand Mesa National Forest issued a Special Use Permit authorizing the development of the site in October 2009, enabling the Center for Snow and Avalanche Studies to complete the GMSP installation just in time for the winter of 2009/2010. Every effort was made to minimize the physical and visual impact of the GMSP installation – all materials were carried into the site, the “footprint” of the installation is very small, and no sensitive resources were disturbed.
Some details about GMSP
The “two tone” tower is white near the base in order to reduce the absorption of solar energy by the tower itself and, thereby, minimize melting and “welling” around the tower base. The upper two-thirds of the tower, conversely, was painted grey so that it will absorb some solar energy and shed occasional accumulations of rime ice; the grey section of the tower also blends into the forest background quite effectively. Instrument arrays are mounted to white arms and plates in order to minimize the heating of the sensors by solar radiation.
The tower has three horizontal arms extending from the mast to the tower’s guywires in order to cause those guywires to enter the snowpack vertically, eliminating the considerable pressures that snow settlement would create on angled guywires, pulling the tower out of “plumb”. A small box located about 40 feet north of the mast contains the batteries being charged by the solar panel on the mast. That box should be buried by snow and out of site for most of the winter, stabilizing the temperature around the batteries to something near 0 degrees C (or 32 F). Two small informational signs are posted some 75-100 feet from the mast. The six white posts located some 25 feet from the mast in a hexagonal array are “height of snow” (HS) stakes.
Occasional visual observation of the depth of the snowpack at each of those stakes will, when referenced to a point adjacent to the tower where HS is being measured automatically, enable researchers to calculate the slope and aspect of the snow surface from which reflected solar energy hits the downward-looking radiation sensors located on the arm extending southward from the mast. That “angle of incidence” has a surprisingly large effect on the calculation of snowpack reflectivity (albedo).
Wind is measured at the top of the mast, approximately 30’ above the ground surface, in order to reduce the effects of local terrain and vegetation. In general, the GMSP site offered all of the attributes sought by the users of the GMSP data – an excellent “sky view” to the east, south, and west enabling radiation monitoring from sunrise to sunset, a large and generally level meadow where wind is less effected by forest cover, and excellent proximity to the avalanche terrain threatening Hwy 65, immediately north of the tower. Of course, having a groomed ski trail leading to the site is an added bonus to the system’s operators!
The public can check near-real-time GMSP weather conditions (wind speed and direction, air temperature, relative humidity, and snowpack depth) at the Colorado Avalanche Information Center’s listings of Weather Observations, at http://avalanche.state.co.us/pub/links_wxobs.php – scroll down to the list of Grand Mesa weather sites and click on the GMSP (Grand Mesa Study Plot) link.