Calibration of MTSAT-1R infrared channels using MODIS/Terra measurements

MODIS/Terra infrared measurements at 3.7, 6.7, 10, 11 µm bands were used for calibrating newly launched Japanese MTSAT infrared channels. The calibration method was tested for August 2005. In order to minimize the navigation error of MTSAT-1R, comparisons were made over the area in which the viewing angle of MTSAT-1R is less than 50° (i.e., 40°N-40°S and 100°E-180°E). Cloud contaminated targets were excluded by applying MODIS cloud flags for intercomparing MTSAT measurements with MODIS values. Collocated match-up data were constructed by considering the differences in spectral response functions, viewing geometry, observation time, and grid space.

Intercomparison indicated that mean biases of two split window and water vapor channels are within about -0.20 K, 0.29 K and 1.40 K, suggesting that accuracies of those three channel measurements are comparable to MODIS measurements. On the other hand, the mean bias of 3.7 µm channel shows a much larger difference of up to -7.23 K, indicating that data quality of 3.7 µm is questionable. Furthermore, the relationship between NIR brightness temperature of MTSAT-1R and of MODIS/Terra appears to be non-linear.