土壤水分微波遥感反演算法及应用研究进展

Recent advances on algorithms and applications of soil moisture retrieval from microwave remote sensing

土壤水分是农作物物候期生长和气候、环境变化的敏感因子,在陆表水气循环过程中发挥着重要作用。本文首先梳理了基于主动微波遥感、被动微波遥感、全球卫星导航系统反射测量(Global Navigation Satellite System Reflectometry,GNSS-R)技术的土壤水分反演算法:1)基于主动微波遥感的裸露地表经验模型、半经验模型、物理散射模型、植被覆盖的水云模型(water cloud model,WCM)和密歇根微波植被散射(Michigan microwave canopy scattering,MIMICS)模型;2)基于被动微波遥感的裸露地表粗糙度模型Q/H、H_(p)、Q_(p)和植被覆盖的τ-ω模型;3)地基、星载GNSS-R土壤水分反演算法。其次,分析了近几十年来微波遥感反演土壤水分的研究进展,提出了进一步精确量化植被和地表粗糙度等土壤水分反演要素的时空变异性是提高反演精度的关键,尤其要考虑植被生长过程及由此导致的电磁波辐射传输机制的不确定性问题。最后,展望了土壤水分在农业生产、陆表水气循环中的应用前景,并指出全球尺度土壤水分对气候变化的响应及反馈机制将是未来的研究热点。

Soil moisture is a sensitive factor for crop phenological growth,climate and environment changes,and it plays an important role in the land surface water and atmospheric circulation.In this paper,the soil moisture retrieval algorithms based on active microwave remote sensing,passive microwave remote sensing and Global Navigation Satellite System Reflectometry(GNSS-R)technology were firstly sorted,including:1)active microwave remote sensing-based empirical model,semiempirical model,physical scattering model for bare ground surface,and water cloud model(WCM),Michigan microwave canopy scattering(MIMICS)model for vegetation coverage;2)passive microwave remote sensing-based Q/H,H_(p),Q_(p) roughness models for bare ground surface andτ-ωmodel for vegetation coverage;3)spaceborne and ground-based GNSS-R soil moisture retrieval algorithms.Secondly,the research and development of soil moisture retrieval from microwave remote sensing in recent decades were reviewed.It was proposed that the key to improve the accuracy of soil moisture retrieval was to quantify accurately the spatial and temporal variability of soil moisture retrieval factors such as vegetation and surface roughness,especially the uncertainty of vegetation growth process and the resulting electromagnetic wave radiation transmission mechanism.Finally,the application outlook of soil moisture in agricultural production and land-surface moisture circulation was prospected,and it was pointed out that the response and feedback mechanism of soil moisture on global scale to climate change would be a research hotspot in the future.