A Fundamental Climate Data Record Derived From AMSR-E,MWRI And AMSR2

Fundamental climate data records(FCDRs)play a vital role in monitoring climate change.This study develops a space-borne passive microwave-based FCDR by recalibrating the Advanced Microwave Scanning Radiometer for Earth Observing System(AMSR-E)on the Aqua satellite,the Microwave Radiometer Imager(MWRI)onboard the Feng-Yun-3B(FY3B)satellite,and the Advanced Microwave Scanning Radiometer-2(AMSR2)onboard the JAXA’s Global Change Observation Mission 1st-Water(GCOM-W1)satellite.Before recalibration,it is found that AMSR-E and AMSR2 observations are stable over time but MWRI drifted colder before May 2015 for most channels and had non-negligible geolocation errors.In addition,inter-sensor differences of brightness temperatures are as large as 5 to 10 K.To improve data consistency and continuity,several inter-sensor calibration methods are applied by using AMSR2 as a reference while MWRI bridging AMSR2 and AMSR-E.Double difference method is used to provide inter-sensor difference time series for correcting calibration biases such as scene temperature-dependent bias,solar-heating induced bias,and systematic constant bias.Hardware differences between sensors are corrected using principal component analysis.Geolocation errors in MWRI are corrected using coastline inflection method.After recalibration,the mean biases of both MWRI and AMSR-E are less than 0.3 K compared to the reference and their standard deviations are less than 1 K for all channels.Under oceanic rain-free conditions,the brightness temperature biases are less than 0.2 K for all channels and no significant relative bias drifts were found between sensors for overlapping observations.These statistics suggest that the consistency between these instruments was significantly improved and the derived FCDR could be useful to obtain long-term water cycle related variables for climate research.