How does the broadband and near-IR surface reflectance of snow vary with the depth and "age" of the snow? Are there differences between urban and rural ares due to the fact that urban snow may get "dirtier" than rural snow?
The reflectance of snow and sea ice is very high relative to other surfaces. Changes in this reflectance due, for example, to the deposition of
black carbon from the atmosphere, can have long-term effects on climate. This reflectance may be a function of the depth and age of the
snow/ice surface and
reflectance may be different in the broadband and near-IR portions of the electromagnetic spectrum.
The same instrument described in the "Surface Reflectance for Monitoring the Health of Vegetation" project described elsewhere
on this website can also be used to monitor the reflectance of snow and ice-covered surfaces. This project has the advantage that amplification
of the signal from a radiometer is probably not necessary because of the high reflectance of snow. All that is required is for upward- and
downward-pointing radiometers be calibrated relatively to each other.
Of course, this project requires snow! But, the equipment can be set up ahead of time in any open area. It might
also be worthwhile to set up two pairs of instruments — one over a grassy surface and one over a paved surface. A mowed field with
no foot traffic is the ideal place for this experiment, because snowfall will produce a uniform white surface. In vegetated areas
with taller grasses, for example, there will be localized melting around clumps of grasses and this will make the data harder to interpret. It
would be interesting to do this experiment over the same kind of surface in an urban and rural environment. Often, snow in urban settings gets
"dirty" relatively quickly, especially if the site is near traffic. This visible change in color is due to black carbon from vehicle exhausts and
this color difference should have a noticeable effect on the surface reflectance.