AMSR2 Brightness Temperature Intercomparison
AMSR2 was launched in 2012 and provides the follow-on to AMSR-E launched in 2002. These two sensors form the basis of a climate data record of microwave-derived global sea surface temperature using the 6 GHz channel. For an accurate determination of variability over this time period, it is essential the sensors be intercalibrated. Due to the sensitivity of microwave brightness temperature to sea surface temperature, an accuracy of 0.5 deg C in sea surface temperature would require an intercalibration of 0.25 K. However, comparisons of AMSR2 to AMSR-E have found inconsistencies of more than 1 K. Further confusing the matter, different calibrations (JAXA and RSS) have shown different temperature dependent offsets between the sensors. Understanding the sensor-based sources of the differences is important to have confidence in long-term variability in this merged data record. Results will be presented showing that differences in nonlinearity characterization are the primary reason for brightness temperature differences between these calibrations. Accounting for this difference does reduce the inconsistency between AMSR2 and AMSR-E, but other yet unexplained sources of channel dependent differences remain.