A Bayesian Deep Image Prior Downscaling Approach for High-Resolution Soil Moisture Estimation

Abstract

Soil moisture (SM) estimation is a critical part of environmental and agricultural monitoring, with satellite-based microwave remote sensing being the main SM source. However, the limited spatial resolution of most current remote sensing SM products reduces their utility for many applications such as evapotranspiration modeling and agriculture management. To address this issue, we propose a Bayesian deep image prior (BDIP) downscaling approach for producing high-resolution satellite SM estimates. More specifically, the high-resolution soil moisture estimation problem is formulated as a maximum a posteriori (MAP) problem, and solved via an encoder-decoder neural network architecture comprising of a deep fully convolutional neural network (FCNN) encoder for modeling the prior spatial correlation distribution of the underlying high-resolution SM variables, and a forward model characterizing the SM degeneration process for modeling the data likelihood. As such, the proposed BDIP approach provides a statistical framework that integrates deep learning with forward modelling in a coherent manner for combining different sources of information, i.e., the knowledge in forward model, the spatial correlation prior, and the remote sensing data and products. Experiments on the downscaling of Soil Moisture Active Passive (SMAP) SM products using the Moderate Resolution Imaging Spectroradiometer (MODIS) products show that SM maps estimated using the proposed method provide greater spatial detail information than other existing downscaling methods, with the SM estimates very close to in-situ measurements.