基于SMAP-R极化反射测量数据监测青藏高原地表冻融状态OA

Spaceborne Global Navigation Satellite System Reflectometry(GNSS-R)is an emerging microwave re-mote sensing technique that has demonstrated significant potential for surface freeze-thaw(F/T)detection.Follow-ing the failure of its active radar instrument,the Soil Moisture Active and Passive(SMAP)satellite was reconfigured to operate in GNSS-R mode,becoming the first spaceborne sensor capable of simultaneously receiving both horizon-tal and vertical polarized GPS L2C signals reflected from the earth's surface.In this study,based on over nine years of SMAP-Reflectometry(SMAP-R)polarimetric observation data,we constructed multiple characteristic indictors,including total power reflectivity,polarization ratio,and normalized third and fourth Stokes parameters,to evaluate the sensitivity to surface F/T states over the Qinghai Xizang(Tibetan)Plateau and the capability in capturing F/T tran-sition dates.The results indicate that different polarimetric parameters exhibit distinct response characteristics to sur-face F/T cycle,showing high temporal consistency with Land Surface Temperature(LST)variations.The total power reflectivity and the normalized fourth Stokes parameter demonstrate specifically the highest sensitivity to F/T state transition,highlighting their superior performance in polarimetric monitoring.This study validates the feasibility of multi-polarization GNSS-R for F/T monitoring in complex plateau environments and offers valuable guidance for the development of future remote sensing products.