Model-Based Interpretation of Summer-To-Fall Transition of Sea Ice MicrowaveSignatures

摘要

This abstract reports that because microwaves can penetrate through cloud fog,and darkness, active and passive microwave instruments provide the primary means of studying sea ice on a large scale basis. Utilization of SAR data for sea ice studies is hampered by the natural spatial and temporal variability of the ice and snow cover as well as sensor induced effects, such as speckle. The most dramatic temporal variability occurs during the seasonal transitions. Here a model based approach is taken to interpret satellite SAR images of sea ice during the summer to fall transition. A Kirchhoff model for surface scattering and a Rayleigh model for volume scattering were used in our study. In summary, the models predict a 6-dB increase in backscattering coefficient and a change in slope from 0.5 dB/degree to approximately 0 dB/degree for ERS-l SAR data. We have also examined the effects of the snow volume scatter and wet snow absorption using field measurements of snow properties. The primary phenomenon affecting the backscatter signature of MY (multiyear) ice in the initial stages of the freeze up is the refreezing of water on the surface and in the upper portions of the ice volume.