Abstract: [Purposes] Interferometric synthetic aperture radar (InSAR)atmospheric water vapor monitoring is based on the principle of differential interferometry,with the inversion result representing the differential precipitable water vapor (ΔPWV),i.e.,a relative measure of PWV.To derive the absolute InSAR PWV values,this study proposes a refined atmospheric water vapor monitoring method by integrating InSAR,BeiDou Navigation Satellite System (BDS),and ERA5 reanalysis data. [Methods] By applying the StaMPS-InSAR technique to 25 Sentinel-1A images over the Jiaodong peninsula region,ΔPWV was retrieved.The InSAR-derived ΔPWV was then spatiotemporally calibrated using BDS PWV and ERA5 PWV to obtain absolute PWV values. [Findings] Results indicate that the correlation coefficients between InSAR PWV and PWV measurements from Qingdao sounding stations,FULS,and RUSH stations all exceed 0.96,with respective root mean square errors (RMSE)of 3.44,2.58,and 2.39 mm.Comprehensive validation demonstrated that InSAR PWV exhibits no significant systematic bias,with overall accuracy exceeding 3.5 mm.Compared with the single BDS calibration approach,the proposed joint BDS-ERA5 calibration method improves accuracy by 16.5%to 28.4%,demonstrating the reliability of the calibration strategy in complex coastal environments. [Conclusions] The proposed method yields absolute PWV with meter-level spatial resolution,effectively capturing fine-scale spatiotemporal variations.This approach provides significant reference value for investigating the distribution and evolution of PWV during extreme precipitation events in complex terrain regions．

Key words: precipitable water vapor, BDS, StaMPS-InSAR, multi-source data fusion, calibrate