Inter-calibration of infrared bands of FY-3C MERSI and VIRR using hyperspectral sensor CrIS and IASI

Abstract

An inter-calibration method of infrared channels of FY-3C MERSI and VIRR using NPP/CrIS and Metop/IASI as the hyperspectral reference sensor is introduced. Based on FY-3C SNO collocated samples with CrIS and IASI, on early orbit, we analyze the calibration biases of infrared bands of MERSI and VIRR. The results show that the brightness temperatures (BT) from the MERSI observation and CrIS have a good consistency, and the BT biases present an approximately normal distribution and the mean BT bias is about -0.18K with standard deviation of 0.83K. When the scene BT is lower than 250 K, the result of MERSI is higher than that of CrIS, while the result of MERSI is lower at the more than 250K scene. The BT from VIRR shows significant systematic bias with respect to CrIS and the mean BT bias is about -0.65 K (channel 4) and -0.72 K (channel 5) at 250K scene with standard deviation of 0.15 K and 0.12 K, respectively. Long term monitoring analysis demonstrates the above biases are stable in the early 6 months. The inter-calibration results using different hyperspectral sensors IASI and CrIS indicate the MERSI/VIRR biases with respect to two reference sensors have a good consistency and this further verifies the reliability of the method. It provides significant information to further correct the calibration biases of MERSI and VIRR.