Anoop et al. (2025) Atmospheric aridity perturbs critical soil moisture thresholds of plant water stress over Indian biomes

Identification

• Journal: Advances in Water Resources
• Year: 2025
• Date: 2025-11-07
• Authors: Sampelli Anoop, Ajinkya Khandare, M. V. Ramana, Subhankar Karmakar, Subimal Ghosh
• DOI: 10.1016/j.advwatres.2025.105169

Research Groups

• Centre for Climate Studies, Indian Institute of Technology Bombay, Mumbai, India
• Earth and Climate Sciences Area, National Remote Sensing Centre, Hyderabad, India
• Environmental Science and Engineering Department, Indian Institute of Technology Bombay, Mumbai, India
• Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India

Short Summary

This study quantifies critical soil moisture thresholds (θcrit) for Indian biomes using satellite data and two independent methodologies, revealing that atmospheric aridity (VPD) significantly perturbs θcrit, leading to seasonal and hydrological forcing-driven variations. The covariance-based method (Cov(GPP-VPD)-SM) is found to be more sensitive for assessing these dynamics.

Objective

• To quantify the critical soil moisture threshold (θcrit) for Indian biomes using two independent methodologies based on satellite data.
• To compare the sensitivity of the evaporative fraction (EF-SM) and covariance between gross primary productivity and vapor pressure deficit (Cov(GPP-VPD)-SM) methods in assessing seasonal dynamics and hydrological forcing impacts on θcrit.
• To understand how atmospheric aridity, specifically Vapor Pressure Deficit (VPD), influences seasonal and rain-irrigation driven variations in θcrit.

Study Configuration

• Spatial Scale: Indian biomes, national scale for India.
• Temporal Scale: Seasonal (monsoon vs. non-monsoon) and event-based (drydowns following rainfall vs. irrigation-driven drydowns) analysis over multiple years.

Methodology and Data

• Models used:
  • Analytical method 1: Dependence of evaporative fraction (EF) on soil moisture (SM) (EF-SM).
  • Analytical method 2: Covariance between gross primary productivity (GPP) and vapor pressure deficit (VPD) under varying SM conditions (Cov(GPP-VPD)-SM).
• Data sources:
  • Soil Moisture Active Passive (SMAP) satellite data for soil moisture.
  • Implicitly, data for Evaporative Fraction (EF), Gross Primary Productivity (GPP), and Vapor Pressure Deficit (VPD) are used, likely from satellite products or reanalysis.

Main Results

• The Cov(GPP-VPD)-SM approach is more sensitive than the EF-SM method for assessing seasonal dynamics and the impacts of varying hydrological forcings on θcrit.
• Critical soil moisture threshold (θcrit) is 0.1205 ± 0.0016 m³/m³ higher during the monsoon season compared to the non-monsoon season across India.
• θcrit during drydowns following rainfall is 0.0377 ± 0.0012 m³/m³ higher than during irrigation-driven drydowns.
• Higher Vapor Pressure Deficit (VPD) in non-monsoon or irrigation-driven scenarios significantly contributes to shaping θcrit.
• The observed distinctions between rainfed and irrigated conditions underscore the importance of employing methods that account for unique hydrological and management characteristics.

Contributions

• Provided a comprehensive quantification of critical soil moisture thresholds (θcrit) for Indian biomes using satellite observations.
• Demonstrated the superior sensitivity of the Cov(GPP-VPD)-SM method over the EF-SM method for capturing seasonal and hydrological forcing impacts on θcrit.
• Quantified significant seasonal and rain-irrigation driven variations in θcrit across India, attributing these variations to atmospheric aridity (VPD).
• Emphasized the critical importance of incorporating VPD into methodologies for computing θcrit and accounting for diverse hydrological and management contexts.

Funding

Not specified in the provided text.

Citation

@article{Anoop2025Atmospheric,
  author = {Anoop, Sampelli and Khandare, Ajinkya and Ramana, M. V. and Karmakar, Subhankar and Ghosh, Subimal},
  title = {Atmospheric aridity perturbs critical soil moisture thresholds of plant water stress over Indian biomes},
  journal = {Advances in Water Resources},
  year = {2025},
  doi = {10.1016/j.advwatres.2025.105169},
  url = {https://doi.org/10.1016/j.advwatres.2025.105169}
}

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