Darand et al. (2026) Long-term spatiotemporal analysis of variation in soil moisture over Iran

Identification

• Journal: Journal of Atmospheric and Solar-Terrestrial Physics
• Year: 2026
• Date: 2026-01-06
• Authors: Mohammad Darand, Ramtin Tashan
• DOI: 10.1016/j.jastp.2026.106727

Research Groups

• Department of Climatology, University of Kurdistan, Sanandaj, Iran
• Board Member of Department of Zrebar Lake Environmental Research, Kurdistan Studies Institute, University of Kurdistan, Sanandaj, Iran

Short Summary

This study analyzed the spatiotemporal variations of surface soil moisture (0–7 cm) across Iran from 1979 to 2024 using ERA5-Land data. The findings revealed an overall decreasing trend in soil moisture, averaging 0.0032 m³ m⁻³ per decade, with the most significant reductions occurring during cold and rainy seasons and in the northeastern regions.

Objective

• To analyze the spatiotemporal variations of surface soil moisture (0–7 cm) across Iran during the period 1979–2024.

Study Configuration

• Spatial Scale: Across Iran, with a spatial resolution of 0.1 degree.
• Temporal Scale: Daily data from 1979 to 2024.

Methodology and Data

• Models used: Not explicitly a model, but the ERA5-Land reanalysis dataset, which is model-driven.
• Data sources: ERA5-Land dataset provided by ECMWF (reanalysis).

Main Results

• The spatial distribution pattern of soil moisture content aligns with the spatial patterns of precipitation, rainy days, and temperature across Iran.
• Soil moisture content across Iran exhibited a decreasing trend, with an average reduction of 0.0032 m³ m⁻³ per decade.
• Temporally, the most substantial reduction in soil moisture occurred during the cold and rainy seasons.
• Spatially, the decrease in soil moisture volume during winter was significantly higher in the northeastern part of the country.
• Conversely, some areas within the Alborz and Zagros highlands showed an increasing trend in soil moisture content.

Contributions

• Provides a long-term (46-year) spatiotemporal analysis of surface soil moisture variations over Iran using high-resolution reanalysis data.
• Identifies specific regional and seasonal trends in soil moisture, highlighting areas of significant decrease (e.g., northeastern Iran, cold/rainy seasons) and increase (e.g., Alborz and Zagros highlands).
• Suggests that observed changes in soil moisture can serve as a potential predictor of climate change, with implications for water resource management, agriculture, flood management, and hydrology.

Funding

• Not specified in the paper.

Citation

@article{Darand2026Longterm,
  author = {Darand, Mohammad and Tashan, Ramtin},
  title = {Long-term spatiotemporal analysis of variation in soil moisture over Iran},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2026},
  doi = {10.1016/j.jastp.2026.106727},
  url = {https://doi.org/10.1016/j.jastp.2026.106727}
}