Enhanced Satellite Monitoring of Dryland Vegetation Water Potential Through Multi‐Source Sensor Fusion.

Drylands are critical in regulating global carbon sequestration, but the resiliency of these semi‐arid shrub, grassland and forest systems is under threat from global warming and intensifying water stress. We used synergistic satellite optical‐Infrared (IR) and microwave remote sensing observations to quantify plant‐to‐stand level vegetation water potentials and seasonal changes in dryland water stress in the southwestern U.S. Machine‐learning was employed to re‐construct global satellite microwave vegetation optical depth (VOD) retrievals to 500‐m resolution. The re‐constructed results were able to delineate diverse vegetation conditions undetectable from the original 25‐km VOD record, and showed overall favorable correspondence with in situ plant water potential measurements (R from 0.60 to 0.78). The VOD water potential estimates effectively tracked plant water storage changes from hydro‐climate variability over diverse sub‐regions. The re‐constructed VOD record improves satellite capabilities for monitoring the storage and movement of water across the soil‐vegetation‐atmosphere continuum in heterogeneous drylands. Plain Language Summary: Drylands provide ecosystem services to more than two billion people but are under threat from global warming and intensifying water stress. We used a machine‐learning method to combine multi‐satellite observations for estimating vegetation water status and seasonal changes over drylands. Our enhanced‐resolution satellite vegetation retrievals (known as vegetation optical depth) were able to delineate diverse vegetation water conditions undetectable from the original 25‐km data record, and showed strong correspondence with in situ plant water measurements. Our approach improves satellite capabilities for monitoring the storage and movement of water across the soil, vegetation, and atmosphere layers in heterogeneous drylands. Key Points: Daily and 500‐m resolution vegetation optical depth (VOD) was derived through multi‐sensor data fusionOptical‐infrared and microwave synergy resolves heterogeneous vegetation water conditions within 25‐km grid cellsRe‐constructed VOD can improve understanding and monitoring of vegetation water potential at plant‐to‐stand scales [ABSTRACT FROM AUTHOR]