Sushmitha et al. (2025) Spatiotemporal trends and drivers of evapotranspiration across india’s diverse climatic zones

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2025
• Date: 2025-11-20
• Authors: Hasanapuram Sushmitha, Thotli Lokeswara Reddy, Kandula Bharghavi, Hemalatha Kapa, K. Krishna Reddy
• DOI: 10.1007/s00704-025-05897-y

Research Groups

• Department of Physics, Yogi Vemana University, Kadapa, Andhra Pradesh, India
• Department of Physics, Rajiv Gandhi University of Knowledge Technologies, Idupulapaya, Vempalli, Andhra Pradesh, India
• Department of H&S (Physics), Marri Laxman Reddy Institute of Technology and Management, Domara Pocham Pally, Hyderabad, Telangana, India

Short Summary

This review comprehensively analyzes spatiotemporal evapotranspiration (ET) trends and their drivers across India's diverse climatic zones, revealing complex regional variations with both increasing and decreasing ET influenced by factors like temperature, solar radiation, and land-use changes. It highlights the critical implications of these trends for water resource management, agricultural productivity, and climate modeling, emphasizing the need for advanced monitoring and region-specific adaptation strategies.

Objective

• To examine the spatiotemporal variations of ET across India’s diverse climatic regions, including trends in ET rates and spatial patterns.
• To investigate the relationships between ET and key climate variables (precipitation, temperature, leaf area index) to understand primary drivers of variability.
• To assess the relationship between ET trends and drought conditions using indices like the Standardized Precipitation Evapotranspiration Index (SPEI).
• To explore the impacts of climate change on ET rates, with a focus on maximum and minimum temperature variations.
• To evaluate the performance of ET estimation methods, such as the Penman-Monteith equation, across India’s diverse climatic conditions.
• To understand the linkage between ET trends, water use efficiency, and carbon uptake by vegetation in different zones.

Study Configuration

• Spatial Scale: India, encompassing diverse climatic zones (tropical wet, tropical dry, montane, arid, semi-arid, subtropical humid, hot arid, hot semi-arid, cold arid, humid, sub-humid) and specific regions (North India, South India, East India, West India, Central India, Gangetic Plains, Western Ghats, Northeastern India, Himalayas, interior peninsular regions).
• Temporal Scale: Multi-decadal, spanning from the early 20th century to the present, with analyses at annual, seasonal, and monthly intervals (e.g., 1901–2010, 1956–2015, 1960–2002, 1961–2011, 2001–2015).

Methodology and Data

• Models used:
  • ET Estimation: FAO-56 Penman-Monteith equation, adjusted Hargreaves equation, simplified multiple linear regression models, weighing lysimeters, eddy covariance systems, Bowen ratio methods, water balance approaches, sap flow measurements, scintillometer, four-source energy balance model (FSU model).
  • Trend Analysis: Mann-Kendall (MK) test, Modified Mann-Kendall (MMK) test, Spearman’s Rho test, linear regression, Innovative Trend Analysis (ITA), Innovative Polygon Trend Analysis (IPTA).
  • Multivariate Analysis: Principal Component Analysis (PCA), Empirical Orthogonal Functions (EOF).
  • Machine Learning: Gene Expression Programming (GEP), Random Forest (RF), Support Vector Machines.
  • Drought Indices: Standardized Precipitation Evapotranspiration Index (SPEI), Standardized Precipitation Actual Evapotranspiration Index (SPAEI), Palmer Drought Severity Index (PDSI), Standardized Precipitation Index (SPI).
  • Hydrological Models: Regional climate models, dynamic vegetation models.
• Data sources:
  • Satellite and airborne remote sensing data (reflected solar radiation, surface temperatures, soil moisture retrievals, gridded data).
  • Ground-based meteorological station data (temperature, humidity, wind speed, solar radiation, precipitation).
  • Pan evaporation measurements.
  • Reanalysis products.
  • Climate model projections (e.g., CORDEX South Asia experiments).

Main Results

• Complex and Variable ET Trends: ET trends across India are highly complex and exhibit significant spatiotemporal variability, with both increasing and decreasing patterns observed across different regions and time periods.
• Regional ET Patterns:
  • Tropical Wet Zone: ET influenced by monsoon seasonality, often reduced by persistent cloud cover.
  • Tropical Dry Zone: Elevated ET rates during prolonged dry seasons dueades to high vapor pressure deficits; some areas experience lengthening dry seasons.
  • Montane Zones: ET generally decreases at higher altitudes, influenced by reduced temperatures and radiation, but complex patterns exist.
  • Arid and Semi-Arid Zones: Overall increasing ET trends, positively correlating with rising temperatures and solar radiation, but regional variations and contradictory findings exist (e.g., decreasing ET despite increasing vegetation in some areas). Human activities account for over 72% of changes in ecosystem indicators in some arid/semi-arid regions.
• Regional Variations within India:
  • North India (Gangetic Plains): Overall increasing ET and potential evapotranspiration (PET), particularly during the monsoon season (July-August).
  • South India (interior peninsular): Mixed trends, with some regions showing decreasing PET and others showing significant increases in maximum/minimum temperature and PET.
  • East India (Northeast): Strong seasonal variations in ET, with maximum latent heat flux during the monsoon; increasing drought conditions in some parts due to decreasing rainfall.
  • West India: Decreasing trends in reference evapotranspiration (RET) observed in Northeast India (as discussed in the West India section of the paper), attributed to declining net radiation and wind speed. Reduced meteorological drought conditions in arid western regions due to lower evaporative demand. Western Ghats forests significantly contribute to monsoon rainfall in neighboring water-deficient regions.
  • Central India: Mixed results, with some areas showing decreasing RET and others projecting increasing RET for the 21st century, influenced by changing rainfall patterns, temperatures, radiation, and wind speeds.
• Underlying Drivers: ET trends are driven by climate change (precipitation variability, net radiation, vapor pressure deficit, temperature changes), land-use and land-cover changes (deforestation, urbanization, agricultural expansion, vegetation dynamics like Leaf Area Index), agricultural practices (irrigation methods, crop types), urbanization and industrialization (impervious surfaces, microclimate alterations), and changes in atmospheric composition (rising CO₂ concentrations affecting plant physiology and water use efficiency).
• Implications: Changes in ET have critical implications for water resource management (decreased water availability, need for adaptive strategies), agricultural productivity (crop water requirements, irrigation demands, conservation practices), ecosystem health (indirectly, through biodiversity and stability), and climate modeling/weather prediction (accurate ET representation for projections and attribution).

Contributions

• Provides a comprehensive synthesis of spatiotemporal evapotranspiration (ET) trends and their drivers across India's diverse climatic zones, integrating findings from numerous studies.
• Highlights the complex and often contradictory regional variations in ET responses to both climatic and anthropogenic factors, such as temperature, solar radiation, land-use changes, and CO₂ fertilization.
• Systematically reviews various measurement methodologies, data sources, and statistical/modeling approaches used for ET estimation and trend analysis, including emerging technologies like remote sensing and AI.
• Identifies critical knowledge gaps in current ET research in India, particularly regarding high-resolution observations, disaggregation of ET components, and the interplay of multiple drivers.
• Proposes clear future research directions, emphasizing the need for enhanced accuracy in ET estimation, improved predictive models, and interdisciplinary approaches to inform sustainable water resource management and climate adaptation strategies in India.

Funding

• Department of Science and Technology (DST) for the INSPIRE Junior Research Fellowship (No. IF210443) awarded to Ms. Hasanapuram Sushmitha.

Citation

@article{Sushmitha2025Spatiotemporal,
  author = {Sushmitha, Hasanapuram and Reddy, Thotli Lokeswara and Bharghavi, Kandula and Kapa, Hemalatha and Reddy, K. Krishna},
  title = {Spatiotemporal trends and drivers of evapotranspiration across india’s diverse climatic zones},
  journal = {Theoretical and Applied Climatology},
  year = {2025},
  doi = {10.1007/s00704-025-05897-y},
  url = {https://doi.org/10.1007/s00704-025-05897-y}
}