A Multimodal Deep Learning Approach for Soil Moisture Downscaling Using Remote Sensing and Weather Data

Understanding soil moisture (SM) dynamics is crucial for environmental and agricultural applications. While satellite‐based SM products provide extensive coverage, their coarse spatial resolution often fails to capture local SM variability. This study presents a multimodal network (MMNet) that integrates remote sensing and weather data to downscale Soil Moisture Active Passive (SMAP) Level‐4 surface SM. We evaluated the performance of MMNet by comparing it with in situ SM observations from the Soil Climate Analysis Network (SCAN) and the United States Climate Reference Network (USCRN) under three scenarios. The results showed that (a) MMNet trained with on‐site data provided accurate SM estimates over time in withheld years; (b) MMNet demonstrated spatial transferability, capturing SM dynamics in regions with sparse or no in situ measurements; and (c) the integration of snapshot and time‐series data was crucial for maintaining the model's accuracy and generalizability across diverse scenarios. The downscaled SM maps demonstrated its potential for producing high‐resolution temporally and spatially continuous SM estimates, which could further support a broad range of environmental and agricultural applications.