Close range 37 GHz passive microwave observations of snow on north and south facing slopes

Topographic aspect geometrically controls the solar flux incident upon the landscape, thereby influencing snow pack thermal metamorphism and consequent physical state and microwave emission characteristics. A time series of 37 GHz vertical polarization radiometer observations was made in an east-west trending gully to investigate the possibility that north- and south-facing slopes may display distinct emission characteristics resulting from differential solar influx. A time lag in brightness temperature between north- and south-facing slopes due to differential timing of melting during the diurnal cycle was observed. Vertical core samples were sieved; the two slopes were not distinguishable on the basis of grain size distribution. Approximately 49% of the sieved snow grains were larger in diameter than the 37 GHz free space wavelength (8.1 mm), suggesting that volume scattering was an important process in this snow pack