2002 年 22 巻 4 号 p. 405-422
The campaign named "Sea ice observation experiment in the Sea of Okhotsk" has been carried out on Lake Saroma and its surrounding area since 1993. The objective of this experiment is to evaluate a possibility of SAR data to monitor sea ice in the Sea of Okhotsk. Lake Saroma is a salt water lake which connects to the Sea of Okhotsk through two channels, and covered with ice in winter time. The salinity, surface roughness and vertical layer structure of the ice are considered to be similar to the thin first-year ice in the Sea of Okhotsk based on the truth data. Therefore, Lake Saroma was selected as one of experimental sites of this study.
The first result we found was that SAR backscattering coefficient decreased as the ice thickened. It was considered that SAR observed a difference of ice surface dielectric constants which were related to the ice thickness. The backscatter from a first-year ice is generally dominated by surface scattering. If the roughness of the ice is known and its effect to the backscattering coefficient is estimated, the backscattering variation caused by the change of dielectric constant can be detected.
RADARSAT has a capability to change the incidence angle to get incidence angle dependencies of the target backscatter. Since the incidence angle characteristic of surface scattering is changed with roughness, there is a possibility to estimate roughness of the target by multi-incidence angle SAR data.
This paper proposes a new method to retrieve ice surface roughness and thickness from RADARSAT multiincidence angle data. This method is applied to the data acquired over Lake Saroma in 1998. The results show reasonable agreements in measured and estimated ice thickness as well as ice surface roughness at Lake Saroma sampling sites.