Abstract
Abstract. The calibration microwave radiometer (CMR) on board the Haiyang-2A (HY-2A) satellite provides wet tropospheric delay correction for altimetry data, which can also contribute to the understanding of climate system and weather processes. The ground-based global navigation satellite system (GNSS) provides precise precipitable water vapor (PWV) with high temporal resolution and could be used for calibration and monitoring of the CMR data, and shipborne GNSS provides accurate PWV over open oceans, which can be directly compared with uncontaminated CMR data. In this study, the HY-2A CMR water vapor product is validated using ground-based GNSS observations of 100 International GNSS Service (IGS) stations along the global coastline and 56 d shipborne GNSS observations over the Indian Ocean. The processing strategy for GNSS data and CMR data is discussed in detail. Special efforts were made in the quality control and reconstruction of contaminated CMR data. The validation result shows that HY-2A CMR PWV agrees well with ground-based GNSS PWV with 2.67 mm as the root mean square (rms) within 100 km. Geographically, the rms is 1.12 mm in the polar region and 2.78 mm elsewhere. The PWV agreement between HY-2A and shipborne GNSS shows a significant correlation with the distance between the ship and the satellite footprint, with an rms of 1.57 mm for the distance threshold of 100 km. Ground-based GNSS and shipborne GNSS agree with HY-2A CMR well.
Highlights
Sea surface height measurement is mainly implemented by satellite altimetry, where the precise tropospheric delay is required to correct the atmosphere propagation error in the measured distance between satellite and sea surface (Obligis et al, 2011)
The HY-2A calibration microwave radiometer (CMR) precipitable water vapor (PWV) is compared to global navigation satellite system (GNSS) PWV, and the results are presented, including the comparison to ground-based GNSS PWV and shipborne GNSS PWV
Ment of shipborne GNSS and HY-2A CMR PWV, where more attention was paid to the GNSS-PWV uncertainty
Summary
Sea surface height measurement is mainly implemented by satellite altimetry, where the precise tropospheric delay is required to correct the atmosphere propagation error in the measured distance between satellite and sea surface (Obligis et al, 2011). The objective of HY-2A is to monitor the dynamic ocean environment with microwave sensors to detect sea surface wind field, sea surface height, and sea surface temperature It is equipped with a dual-frequency (13.58 and 5.2 GHz) altimeter, a calibration microwave radiometer (CMR), a microwave. GNSS PWV from coastal stations and especially that from moving platforms over the ocean could be a resource with higher accuracy and resolution for validating and potential calibrating of HY-2A CMR data.
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