A comparison of microwave radiometric data and modeled snowpack conditions for dye 2, Greenland

Meteorological observations were recorded at Dye 2, Greenland, during the summer of 1993 as part of a research program to identify interannual variations in melt occurrence on the Greenland ice sheet from satellite microwave data. The meteorological observations were used to drive an energy-balance model of the snowpack during 21 June to 13 July 1993. Time series of the meteorological observations and various model outputs were compared to a concurrent time series of Special Sensor Microwave/Imager(SSM/I) data for scan cells centered within 25 km of Dye 2. The satellite microwave observations clearly show an increase in snowpack emissivity at the same time that the model indicates liquid water forming in the snow. Diurnal melt-freeze cycles that occurred during mid June to early July resulted in an increase in the 37 GHz brightness temperature as great as 60 K from the dry, refrozen snow in the morning to the wet snow of some afternoons. The effects of fresh snowfall, which tend to increase the brightness temperature, and of snow growth from melt-freeze metamorphism, which tend to decrease the brightness temperature, are also apparent in the microwave observations. The results of this work demonstrate the influence of daily weather variations on the microwave emissivity in the ice sheet's percolation zone and the usefulness of swath data to diagnose the diurnal cycle of melt.