Pegas et al. (2026) A Comprehensive Evaluation of Evapotranspiration in Mainland Portugal Based on Climate Reanalysis Data

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Identification

• Journal: Atmosphere
• Year: 2026
• Date: 2026-02-18
• Authors: João Pedro Pegas, João Filipe Santos, María Manuela Portela
• DOI: 10.3390/atmos17020215

Research Groups

Not explicitly stated in the provided text.

Short Summary

This study comprehensively compares spatial patterns of potential and reference evapotranspiration (Ep and Eto) derived from various models and high-resolution datasets over mainland Portugal (1980–2023) and analyzes Eto trends, revealing an overall increase in atmospheric evaporative demand, particularly in recent decades, suggesting a progressively longer dry season.

Objective

• To conduct a comprehensive comparative analysis of the spatial patterns of potential (Ep) and reference (Eto) evapotranspiration at a 0.1° spatial resolution using daily data from two high-resolution datasets (GLEAM and ERA5-Land) and three models (Thornthwaite, Hargreaves–Samani, and Penman–Monteith) over mainland Portugal.
• To perform trend analyses of Eto magnitudes on a monthly and annual basis in a gridded format for the period 1980–2023.

Study Configuration

• Spatial Scale: Mainland Portugal, at a 0.1° spatial resolution.
• Temporal Scale: 44-year reference period (1980–2023), using daily data for comparisons and monthly/annual data for trend analyses.

Methodology and Data

• Models used: Thornthwaite, Hargreaves–Samani, and Penman–Monteith models for evapotranspiration estimation.
• Data sources: GLEAM (Global Land Evaporation Amsterdam Model) dataset, ERA5-Land reanalysis dataset, and gridded meteorological data (implied for model inputs).

Main Results

• Spatial distributions of Ep and Eto show higher values in milder, flatter southern Portugal and lower values in cooler, mountainous northern regions.
• The Penman–Monteith model exhibited the highest reliability in estimating evapotranspiration.
• The Thornthwaite model generally underestimated evapotranspiration across the country.
• The Hargreaves–Samani model showed underestimation in coastal areas.
• Trend analysis of Eto indicates an overall increase in atmospheric evaporative demand over the full 1980–2023 study period.
• This increase was more pronounced during the recent 22-year period (2002–2023) compared with the earlier period (1980–2001).
• Statistically significant increases in Eto were observed in August and October, potentially reflecting a climate shift towards a progressively longer dry season.

Contributions

• Provides a comprehensive comparative analysis of Ep and Eto spatial patterns using multiple high-resolution datasets and established models for mainland Portugal.
• Offers a detailed and long-term (44-year) trend analysis of Eto, highlighting the acceleration of evaporative demand in recent decades.
• Identifies the most reliable evapotranspiration estimation model (Penman–Monteith) and the biases of others (Thornthwaite, Hargreaves–Samani) for the study region.
• Contributes to understanding climate change impacts on hydrological processes and water resource management by indicating a potential shift towards a longer dry season.

Funding

Not explicitly stated in the provided text.

Citation

@article{Pegas2026Comprehensive,
  author = {Pegas, João Pedro and Santos, João Filipe and Portela, María Manuela},
  title = {A Comprehensive Evaluation of Evapotranspiration in Mainland Portugal Based on Climate Reanalysis Data},
  journal = {Atmosphere},
  year = {2026},
  doi = {10.3390/atmos17020215},
  url = {https://doi.org/10.3390/atmos17020215}
}