Intercalibration of microwave sounding unit with short overlaps

摘要

NOAA/NESDIS/Center for Satellite Applications and Research has been reprocessing and recalibrating the Microwave Sounding Unit (MSU) observations to generate atmospheric temperature dataset with climate quality. So far, observations from the MSU channels 2, 3, and 4 for NOAA 10, 11, 12, and 14 have been recalibrated using a recently-developed SNO (simultaneously nadir overpasses) sequential nonlinear calibration technique and a 20-year long deep-layer atmospheric temperature dataset from 1987 to 2006 has been generated. However, when using the SNO nonlinear technique to intercalibrate the MSU instrument for satellites before NOAA 10, one has to deal with the short overlap issue for satellites between NOAA 9 and NOAA 10. In this study, by extending the spatial distance criterion for the SNO matchups, we generate more SNO samplings for the short-overlapping satellites. We analyze the error characteristics of the SNO matchups when the spatial distance is extended to as large as 650km. We also generate calibration coefficients using the SNO nonlinear sequential intercalibration technique and then analyze how the intercalibration affects the SNO biases with different separation distances. These analyses will be helpful in determining the final calibration coefficients used for generating consistent MSU long-term temperature time series that will include all available satellites.