Impact of temporal variations in vegetation optical depth and vegetation temperature on L-band passive soil moisture retrievals over a tropical forest using in-situ information

A significant improvement of up to 45% in soil moisture (SM) retrieval accuracy over tropical forests was achieved by optimizing vegetation optical depth (τ) and scattering albedo (ω). The study, conducted at the UNESCO World Heritage Site Calakmul, Mexico, found that τ varied temporally between 1.0 and 1.7, while ω remained constant at 0.0655. Using in-situ soil and vegetation temperatures with these optimal values reduced the unbiased root-mean-square difference (ubRMSD) from 0.049 to 0.128 m³/m³ to 0.035–0.070 m³/m³. The research also highlighted that vegetation temperature was the most sensitive parameter, with discrepancies up to 10 K affecting SM estimates. These findings offer a pathway for enhancing satellite-based SM retrievals over forests, as demonstrated by comparing Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) data with in-situ measurements.

Monsiváis-Huertero, A., Hernández-Sánchez, J. C., Jiménez-Escalona, J. C., Galeana-Pizaña, J. M., Constantino-Recillas, D. E., Torres-Gómez, A. C., Magagi, R., Goïta, K., & Couturier, S. (2019). Impact of temporal variations in vegetation optical depth and vegetation temperature on L-band passive soil moisture retrievals over a tropical forest using in-situ information. International Journal of Remote Sensing, 41(6), 2098–2139. https://doi.org/10.1080/01431161.2019.1685715