Accuracy assessment of sea-ice concentrations from MODIS using in-situ measurements

The Moderate Resolution Imaging Spectroradiometer (MODIS) potential open water algorithm (MPA) uses infrared satellite images to retrieve sea-ice concentration. From these data, composite maps of the sea-ice concentration are generated at up to 1-km resolution, in order to serve as input for high-resolution atmospheric models. In the present study, aircraft and helicopter-based measurements from the field experiment “Atmospheric Boundary layer and Sea-ice Interaction Study” (ABSIS) are used to validate the MPA-based sea-ice concentration maps with in-situ measurements: Aircraft measurements of upwelling longwave radiation are used to derive reference values of the sea-ice concentration. MPA-based maps are checked for accuracy of sea-ice concentration values as well as for the preservation of the sea-ice concentration distribution function. This error analysis yields that sea-ice concentration can be determined from MODIS data with approximately ±10% error. The compilation of composite maps from multiple overpasses leads to an overall uncertainty of ±11.5%. Helicopter-based measurements of the sea-ice thickness are used to study the dependence of MPA-based sea-ice concentration with respect to sea-ice thickness. The dependence turns out to be minimal. Finally, MPA sea-ice concentration is compared to the popular Special Sensor Microwave Imager (SSM/I) sea-ice concentration data. Both data sets are found to agree within ±7%.