Radiative transfer based cross-calibration of passive microwave measurements obtained from satellites

A number of Earth observing satellite missions carrying onboard passive microwave instruments operate in frequency channels in close proximity in terms of frequency, polarization, incidence angle, system noise, etc., which, however, results in difference in their measurements. In order to remove such differences in the measurements from two or more sensors, cross-calibration of brightness temperature may be desired. Present study provides a procedure to calibrate such measurements from one sensor with another while they do not need to have any common period of operation. Study demonstrates the technique using measurements from AMSR-2 and TMI onboard GCOM-W1 and TRMM. Relationships between their corresponding channels are established using radiative transfer simulations. The relationship thus established when applied to their actual near-concurrent observations found to have the root mean square error of 3.15 K to 6.18 K between them compared to 3.71 K to 10.4 K found without calibration.