Validation of the“HY-2”altimeter wet tropospheric path delay correction based on radiosonde data

摘要

Wet tropospheric path delay (PD) is a highly variable term for the altimeter measurement of a sea surface height, caused by the refraction effect of atmospheric water vapor and cloud liquid water. In order to esti-mate PD values, the“HY-2”system includes a calibration microwave radiometer (CMR) operating at 18.7, 23.8 and 37 GHz. The PD data of the CMR were compared and validated by coincident radiosonde profiles from ten globally distributed radiosonde stations during October 2011 to August 2012. The temporal interval was 1 h. In order to avoid land contamination, different spatial intervals between these two data sets were tested. The empirical fit function of PD uncertainty and spatial interval was found and extrapolated to the ideal situation that the data of CMR and radiosonde were totally coincident. The stability of the brightness temperature of the CMR and its impact on the PD correction was also studied. Consequently, the uncer-tainty of the PD algorithm of the CMR was estimated to be 2.1 cm.