About the Project
The Community Collaborative Rain, Hail, and Snow CoCoRaHS Network started in 1998 as a community-based network of weather observer volunteers in Colorado and is today the single largest provider of daily precipitation observations in the United States (US).
In this project, we embrace the CoCoRaHS mission to use low-cost measurement tools, provide training and education, and utilize an interactive website to collect high quality snow albedo, snow depth, and snow density data for research and education applications.
What is Albedo?
Albedo is a measure of surface reflectivity, defined as the ratio of reflected energy to incoming solar energy. Albedo is a unitless quantity typically expressed as a value between 0 and 1.0. To illustrate the effect of albedo on climate, ask yourself the following question:
What color tee shirt you would wear on a sunny day? Black or white?
If you chose white, you already know the effect albedo has on climate! White tee shirts reflect incoming solar energy and help you stay cool. A black tee shirt absorbs the incoming solar energy and makes you warmer.
How does land cover affect albedo and climate?
Surfaces like snow and ice have high albedo (0.8-0.9) and reflect much of the sun’s energy (Figure 1). Dark surfaces like forest canopies and pavement have low albedo (0.05-0.15) and absorb the sun’s energy to warm the Earth’s surface. Just as a white tee shirt helps to keep your body cool, snow and ice have help to cool the land surface. Dark forest canopies and pavement act like a black tee shirt on the landscape and serve to warm the Earth’s surface. During periods of snow cover, forest canopies are easily distinguished from deforested areas in satellite images because the dark forest canopy shields the highly reflective snow (Figure 2).
When humans change the landscape, one of the ways they affect climate is though changes in surface albedo. As an example, try to envision the landscape in New England during an 1850 winter. In New Hampshire, over 50% of the forests had been removed (Figure 3) to make way for sheep and cow pasture, to heat homes, and to fuel a booming lumber and paper industry. Without dark forest canopies, the snow-covered New England landscape would have had a much higher albedo, which likely had a strong cooling effect. But how much of cooling effect? In this project we hope to answer that question.
Figure 1. Albedo effects of land surfaces without snow and with snow
Figure 2. Moderate Resolution Imaging Spectroradiometer(MODIS)true-color satellite image of snow cover covering much of New England on 17-February-2007.
Figure 3. Historical forest cover in New England from Wildlands and Woodlands (Foster et al. 2010), full report available here