Adarsh et al. (2026) Analysing the Hydro-Meteorological synchronization of reference evapotranspiration across Indian Mainland using cross recurrence approach

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2026
• Date: 2026-01-19
• Authors: S Adarsh, M Athira, Ali Najah Ahmed, Ahmed El-Shafie, N Salman
• DOI: 10.1007/s00704-026-06018-z

Research Groups

• TKM College of Engineering, Kollam, India
• Department of Engineering, School of Engineering and Technology, Sunway University, Selangor Darul Ehsan, Malaysia
• National Water and Energy Center, United Arab Emirates University, Al Ain, United Arab Emirates

Short Summary

This study analyzed the dynamic behavior and hydro-meteorological synchronization of monthly reference evapotranspiration (ET₀) across 14 agro-climatic zones in India (2000–2020) using Recurrence Quantification Analysis (RQA) and Cross Recurrence Quantification Analysis (CRQA), revealing distinct spatial patterns of ET₀ predictability and varying influences of meteorological drivers across zones.

Objective

• To investigate the recurrence dynamics of ET₀ across India’s 14 agro-climatic zones using high-resolution ERA5 data from 2000 to 2020, applying Recurrence Quantification Analysis (RQA).
• To apply the Cross Recurrence Quantification Analysis (CRQA) technique to quantify the influence of meteorological variables on ET₀ recurrence.

Study Configuration

• Spatial Scale: Indian mainland, spanning 8° to 37°N latitude and 68° to 97°E longitude, divided into 14 agro-climatic zones (4,642 grid points) with a 0.25° × 0.25° spatial resolution.
• Temporal Scale: 2000–2020 (21 years), daily meteorological data used to calculate monthly ET₀.

Methodology and Data

• Models used:
  • FAO-56 Penman-Monteith method (for ET₀ calculation)
  • Recurrence Quantification Analysis (RQA)
  • Cross Recurrence Quantification Analysis (CRQA)
  • Phase-space reconstruction (PSR)
  • Average Mutual Information (AMI) (for optimal time delay)
  • False Nearest Neighbor (FNN) method (for embedding dimension)
  • Monte Carlo permutation testing (for statistical significance)
• Data sources:
  • ERA5 reanalysis dataset (high-resolution, daily temporal and 0.25° × 0.25° spatial resolution)
  • Meteorological variables: maximum and minimum temperatures, dew point temperature, relative humidity (RH), wind speed (at 2 meters), solar radiation, and atmospheric pressure.

Main Results

• RQA revealed distinct spatial patterns in ET₀ dynamics: coastal zones (e.g., Western Coastal Plain and Hills) exhibited stable, periodic, and predictable ET₀ behavior (high Lmax of 196.0, Determinism (DET) of 0.78, Clustering Coefficient (CC) of 0.79), while arid (e.g., Western Desert) and mountainous regions (e.g., Eastern and Western Himalayas) displayed chaotic, less predictable, and erratic dynamics (low Lmax of 8.0 and 3.0, DET of 0.34 and 0.14, respectively).
• CRQA demonstrated spatially heterogeneous coupling between ET₀ and meteorological drivers across India's agro-climatic zones.
• Temperature and solar radiation emerged as strong, consistent drivers of ET₀ in arid and semi-arid regions (e.g., Western Dry Region, Gujarat Plains & Hills, with DET values exceeding 60% for solar radiation and 69.64% for temperature).
• Humidity and pressure played stronger roles in humid and high-altitude zones (e.g., Middle Gangetic Plains, East Coast Plains & Hills, Southern Plateau & Hills showed high DET for pressure; Central Plateau & Hills, Western Plains & Hills, Gujarat Plains & Hills showed high DET for relative humidity).
• Wind speed's influence on ET₀ was regionally variable, acting as a strong driver in arid/semi-arid regions (e.g., Western Dry Region, Gujarat Plains & Hills with DET values 44.77%–58.27%) but showing weak or chaotic relationships in complex terrain (e.g., Eastern Himalayas, Central Plateau & Hills with low DET values 16.24%–17.07%).
• Monte Carlo permutation analysis confirmed the statistical significance and spatial heterogeneity of ET₀-climate coupling, indicating that most CRQA parameters did not show significant spatial uniformity (p-values generally ≥ 0.05), underscoring the importance of local climatic and topographic factors.

Contributions

• This study provides the first comprehensive analysis of the recurrence characteristics of reference evapotranspiration (ET₀) across India’s diverse agro-climatic zones using advanced nonlinear dynamical techniques (RQA and CRQA).
• It offers a nuanced understanding of ET₀ variability and its complex, spatially explicit coupling with various meteorological drivers at regional scales.
• The findings highlight the limitations of uniform hydrological models and advocate for the development of tailored, region-specific water resource management strategies, improved irrigation planning, drought forecasting, and climate adaptation policies in agriculture.

Funding

No funding received to perform this research work.

Citation

@article{Adarsh2026Analysing,
  author = {Adarsh, S and Athira, M and Ahmed, Ali Najah and El-Shafie, Ahmed and Salman, N},
  title = {Analysing the Hydro-Meteorological synchronization of reference evapotranspiration across Indian Mainland using cross recurrence approach},
  journal = {Theoretical and Applied Climatology},
  year = {2026},
  doi = {10.1007/s00704-026-06018-z},
  url = {https://doi.org/10.1007/s00704-026-06018-z}
}