Comparison of ground-based and airborne snow surface albedo parameterizations in an alpine watershed: Impact on snowpack mass balance

Two commonly used snow surface albedo models were evaluated using albedo data from the Airborne Visible/Infrared Imaging Spectroradiometer (AVIRIS), and their influence on snowmelt timing and magnitude was assessed using a net radiation/temperature index snowmelt model, a series of satellite-based snow covered area scenes, and on-site snow surveys. Albedo estimates using an explicit representation of snow surface temperature, snow age, and solar illumination angle, based on the Biosphere Atmosphere Transfer Scheme (BATS), were within the 0.02 AVIRIS measurement error for 78% of the snow-covered portions of the watershed. Conversely, albedo values estimated using a simple model based solely on snow surface age underestimated AVIRIS-observed albedo. Correlations between the timing of snowmelt and observed runoff using the BATS albedo model (R2 = 0.69) were significantly better than those using the age-based approach (R2 = 0.59) and were comparable to using AVIRIS data (R2 = 0.73). Snow extent was simulated most accurately with the AVIRIS parameterization; average map accuracy was 79 and 10% greater than when using the age-based and BATS albedo parameterizations, respectively. The error in snow water equivalent for April was 14% for BATS versus 39% for the age-based albedo; however, it was less than 1% for simulations using AVIRIS albedo data. Thus the BATS albedo estimates performed better than the age-based albedo but did not outperform simulations using AVIRIS albedo data.