Evapotranspiration Dynamics in Climate Systems

Evapotranspiration, the combined process of evaporation from land and water surfaces and transpiration through vegetation, is a central component of the terrestrial water cycle and exerts profound influence on regional and global climates. It governs the partitioning of incoming solar energy between sensible and latent heat fluxes, thereby modulating surface temperatures, humidity profiles and atmospheric circulation patterns. Variations in evapotranspiration arise from changes in net radiation, air temperature, humidity, wind speed and vegetation cover, and may be further shaped by large-scale oscillations such as the Pacific Decadal Oscillation. Observed trends over recent decades display both increases and decreases in reference evapotranspiration across different regions, leading to the so-called ‘evaporation paradox’ in which rising temperatures do not always coincide with enhanced atmospheric water demand. Understanding these dynamics is essential for water resource management, agricultural planning and climate-change impact assessments. Contemporary research integrates long-term observations, micrometeorological experiments, satellite-derived vegetation indices and process-based models to disentangle the relative contributions of atmospheric demand, land-surface characteristics and ocean–atmosphere coupling to observed evapotranspiration trends. Such insights inform projections of future drought risk, catchment water balance and feedbacks to regional climate under various warming scenarios.

Research from Nature Portfolio

Periodic analyses of reference evapotranspiration across a vast continental network of meteorological stations reveal that decadal shifts rather than monotonic trends characterise long-term variability. In one comprehensive study, decadal declines in net radiation and reductions in near-surface wind speed were identified as the dominant controls on reference evapotranspiration before the early 1990s, particularly in southern regions. After this period, relative humidity limitations driven by broader ocean–atmosphere interaction patterns emerged as principal drivers of enhanced evaporation capability. These findings suggest that episodic climate modes, such as the Pacific Decadal Oscillation, imprint a punctuated rather than uniform signal on evapotranspiration dynamics at continental scale.

Evapotranspiration Dynamics in Climate Systems publication trend

The graph below shows the total number of articles in evapotranspiration dynamics in climate systems across all publications each year (not limited to Nature Index journals).

Technical terms

Evapotranspiration: Combined water transfer to the atmosphere via evaporation from surfaces and plant transpiration.

Reference evapotranspiration (ET₀): Standardised estimate of evaporative demand from a reference grass surface under well-watered conditions.

Potential evapotranspiration (PET): Maximum possible evapotranspiration assuming unlimited soil moisture and adequate vegetation cover.

Vapour pressure deficit (VPD): Difference between saturation vapour pressure and actual vapour pressure of air, indicating atmospheric thirst for moisture.

Penman–Monteith equation: Physically based model combining energy balance and aerodynamic terms to estimate reference evapotranspiration.

References

1. Periodic fluctuation of reference evapotranspiration during the past five decades: Does Evaporation Paradox really exist in China?. Scientific Reports (2016).
2. Why has catchment evaporation increased in the past 40 years? A data-based study in Austria. Hydrology and Earth System Sciences (2018).
3. Sensitivity of potential evapotranspiration to changes in climate variables for different Australian climatic zones. Hydrology and Earth System Sciences (2017).