An Intercomparison of DMSP F11- and F13-Derived Sea Ice Products

Passive microwave satellite data provide an extended time series for monitoring of polar processes, such as variability in sea ice extent. To ensure consistent data sets for time series analysis of sea ice cover, differences between ice concentration estimates from similar sensors on successive spacecraft must be understood. In this study, the effects of changing from the SSM/I F11 to the F13 satellite are examined for a 5-month overlap period. In terms of hemispheric averages of mean ice concentration, the biases introduced by the switch from F11 to F13 are slight and are not statistically significant in most areas, although relatively large and significant differences are seen in some regions. Furthermore, differences in sea ice extent and total ice covered area between the two platforms were found to be statistically significant. Previous efforts to reduce such differences in geophysical parameters between earlier SSM/Is have focused on establishing relationships between the brightness temperatures. However, we find the relations between the F11 and F13 brightness temperatures to be highly sensitive to the region chosen for the analysis. Consequently, the choice of sample has a substantial effect on the sensor-to-sensor adjustment and on the resulting sea ice concentrations. Furthermore, analysis of ice concentrations between F8 and F11 and between F11 and F13 shows that current attempts at a relative calibration of the two instruments do not offer a significant improvement in corresponding ice fractions.