Turman et al. (2026) High-Resolution SMAP Soil Moisture in Agriculture: Capturing Field-Scale Variability in Soil Moisture and Evapotranspiration in the San Luis Valley

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Identification

• Journal: Remote Sensing
• Year: 2026
• Date: 2026-08-02
• Authors: Annelise M. Turman, Bin Fang, Ryan G. Smith, Steve Blecker, V. Lakshmi
• DOI: 10.3390/rs18152514

Research Groups

Not specified in the provided text.

Short Summary

This study evaluates a new 400 m resolution soil moisture product derived from 36 km SMAP observations, demonstrating its superior ability to discern field-scale variability in irrigation and crop types compared to the standard 9 km product in the San Luis Valley, Colorado.

Objective

• To determine if a 400 m downscaled soil moisture (SM) product provides enhanced field-scale discrimination of SM variability compared to the existing 9 km SMAP product.

Study Configuration

• Spatial Scale: San Luis Valley, Colorado (resolutions compared: 400 m, 9 km, and 36 km).
• Temporal Scale: Seasonal and interannual (analysis includes seasonal water management and recent trends).

Methodology and Data

• Models used: Downscaling algorithm, Rotated Empirical Orthogonal Function (REOF) analysis, and Rotated Principal Component Analysis (PCA).
• Data sources: Soil Moisture Active Passive (SMAP) observations, Climate Hazards Group InfraRed Precipitation with Station (CHIRPS), and Moderate Resolution Imaging Spectroradiometer (MODIS) evapotranspiration (ET) data.

Main Results

• The 400 m SM product exhibits significantly higher sensitivity to crop types, irrigation methods, ET, and planting/harvesting dates than the 9 km product.
• Correlation between MODIS ET and SM is stronger for the 400 m product (0.457) than for the 9 km product (0.392).
• Flood-irrigated fields show higher SM and ET levels compared to sprinkler-irrigated fields.
• REOF analysis indicates that the 400 m product can detect field-scale trends related to seasonal water management, while the 9 km product is limited to basin-wide changes.
• Both products successfully detect basin-wide responses to snowmelt and a recent increase in SM at higher elevations.
• Rotated PCA of the 400 m product reveals seasonal patterns concentrated over irrigated fields and increased runoff following winters with high snow water equivalent.

Contributions

• Validates a high-resolution downscaling algorithm that enables field-scale agricultural monitoring, providing a significant improvement over existing 9 km SMAP products for detecting localized water management practices.

Funding

Not specified in the provided text.

Citation

@article{Turman2026HighResolution,
  author = {Turman, Annelise M. and Fang, Bin and Smith, Ryan G. and Blecker, Steve and Lakshmi, V.},
  title = {High-Resolution SMAP Soil Moisture in Agriculture: Capturing Field-Scale Variability in Soil Moisture and Evapotranspiration in the San Luis Valley},
  journal = {Remote Sensing},
  year = {2026},
  doi = {10.3390/rs18152514},
  url = {https://doi.org/10.3390/rs18152514}
}