Estimating gravimetric corn water content using L-band passive microwave airborne data during HiWATER

Abstract

In this study, we developed a new algorithm to retrieve the gravimetric vegetation water content (GVWC, %) of corn using L-band bi-angular dual-polarized passive microwave TB, corn LAI, height of the corn stalks and areal density of the corn stalks. Based on in-situ measured corn-related three-dimensional structure parameters during various growth stages, simulation databases of corn LAI and optical depth in L-band were established. A quantitative relationship between corn GVWC, corn optical depth in L-band, corn LAI, height and areal density of the corn stalks was constructed based on the simulation databases. The corn optical depth in this quantitative relationship was calculated by the retrieval method of low-vegetation optical depth proposed by Wang et al. We used Polarimetric L-band Microwave Radiometer (PLMR) airborne data obtained in the 2012 Heihe Watershed Allied Telemetry Experimental Research (HiWATER) project, and the leaf area index (LAI) product of LAINet wireless network to retrieve the GVWC of corn in study area. In-situ measured corn GVWC were used to validate the accuracy of the retrieved corn GVWC. The results show that the GVWC retrieval method proposed in this study is feasible for monitoring corn GVWC in real time. Moreover, the method is promising to apply to the satellite observations.