The effect of spatial variability on the sensitivity of passive microwave measurements to snow water equivalent

In all test cases, this study finds that there exists sensitivity of microwave brightness temperature (Tb) to total snow depth contained within the measurement footprint, regardless of the heterogeneous nature of snow pack properties. Across three study areas, Tb decreases by 23-35 K as depth increased up to the signal saturation depth, which ranged from 70 to 120 cm. With regard to vegetation sensitivity, forest fractions (F) as little as 0.2 can modify the PM measurement by up to 10 K, and F greater than 0.6 mask virtually all of the microwave signal attributable to snow. Finally, with respect to the measurement scale, our results indicate that the scale at which the PM measurement is made does not affect the sensitivity of the Tb to mean snow depth, to the scale (1 km) examined herein.