Soil moisture monitoring in agricultural lands via active-passive microwave remote sensing

Abstract

Soil moisture is a critical element for monitoring crop growth and drought in agricultural lands.Microwave remote sens-ing is a reliable mode of retrieving soil moisture in real time and under all weather and physiographic conditions.Retrieving soil moisture via combined active and passive microwave remote sensing has the advantage of high spatial resolution and real-time mea-surement at regional scale.Although it has practical significance for agricultural lands,this technique has largely been previously applied in retrieving soil moisture under natural vegetation.Here,the technique was used to retrieve soil moisture in agricultural lands.The TRMM Microwave Imager(TMI) emissivities at different soil moisture and surface roughness conditions were simulated using the Advanced Integral Equation Model(AIEM).After emissivity sensitivity analysis of soil moisture and roughness,a soil moisture inversion model for bare surfaces via passive microwave remote sensing was established based on the parameterized mi-crowave radiation model(Qp model).The inversion algorithm for vegetated surface was established using the microwave radiation transfer model(ω-τ model).Then a soil moisture variation inversion algorithm that combines active and passive microwave remote sensing(using TRMM Microwave Imager and Precipitation Radar data) was developed based on the Simple Scattering Model(SSM) and Geometry Optical Model(GOM).The daily soil moisture variations in agricultural lands between 30o-38oN and 110o-120oE was estimated for January through April of 2008.The retrieved daily soil moisture variations were compared with interpolated daily pre-cipitation variations at the grid which is located at 34.45oN and 119.25oE in the croplands of Lianyungang,Jiangsu Province.The study showed that microwave remote sensing was practicable in monitoring and managing soil moisture in agricultural lands.