An assessment of sea ice thickness calculated from AMSR-E and MODIS for operational data assimilation

In this paper, sea ice thickness values are calculated for a region along the east coast of Canada using data from two sensors representative of those available for operational data assimilation. Data from the first sensor, the Moderate Resolution Imaging Spectroradiometer (MODIS), is used to calculate the ice thickness using a heat balance equation. Relationships between the MODIS ice thickness and polarization ratio from the Advanced Microwave Scanning Radoimeter-Earth Observing System (AMSR-E) are used to calculate thickness of thin ice (less than 0.2m) from the AMSR-E data. This is done for each frequency on the AMSR-E sensor in the range of 6.9GHz to 36.5GHz. Through comparison with data from ice charts it is found that the errors are lowest for thickness values calculated from low frequency AMSR-E data. The accuracy of the ice thickness from both MODIS and AMSR-E is and that from operational ice charts are further assessed using the triple collocation method. It is found that the error associated with ice thickness from AMSR-E is the lowest of the three, and the error associated with ice thickness from MODIS is the highest. While the MODIS data represent the small scale variability of the sea ice thickness better that the AMSR-E data, the MODIS data can produce spurious values of ice thickness due to unmasked clouds. It is concluded that both data sources may be useful for operational assimilation, however quality control would need to be applied to the MODIS data to remove spurious values of thick ice.