Differences between air and snow surface temperatures during snow evaporation

When using the bulk aerodynamic formula for computing snow evaporation from the snowpack surface, investigators often only have access to air temperature measurements, and are forced to assume that snowpack surface temperature is the same as air temperature, at least for temperatures below 0°C. However, one of the main sources of energy for snow evaporation is air-to-snow sensible heat transfer. Such a transfer may require the snow to be substantially cooler than the overlying air. And measurements of snow surface temperatures do reveal temperatures often much colder than those of the air. In such situations, assuming equal air and snow surface temperature will result in the over-estimation of snow evaporation. -Authors