Evapotranspiration seasonality across the Amazon Basin
Evapotranspiration (ET) of Amazon forests is a main driver of regional climate patterns and an important indicator of ecosystem functioning. Despite its importance, the seasonal variability of ET over Amazon forests, and its relationship with environmental drivers, is still poorly understood. In...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-06-01
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| Series: | Earth System Dynamics |
| Online Access: | https://www.earth-syst-dynam.net/8/439/2017/esd-8-439-2017.pdf |
| Summary: | Evapotranspiration (ET) of Amazon forests is a main driver of
regional climate patterns and an important indicator of ecosystem
functioning. Despite its importance, the seasonal variability of ET over
Amazon forests, and its relationship with environmental drivers, is still
poorly understood. In this study, we carry out a water balance approach to
analyse seasonal patterns in ET and their relationships with water and energy
drivers over five sub-basins across the Amazon Basin. We used in situ
measurements of river discharge, and remotely sensed estimates of terrestrial
water storage, rainfall, and solar radiation. We show that the
characteristics of ET seasonality in all sub-basins differ in timing and
magnitude. The highest mean annual ET was found in the northern Rio Negro
basin (∼ 1497 mm year<sup>−1</sup>) and the lowest values in the
Solimões River basin (∼ 986 mm year<sup>−1</sup>). For the first
time in a basin-scale study, using observational data, we show that factors
limiting ET vary across climatic gradients in the Amazon, confirming
local-scale eddy covariance studies. Both annual mean and seasonality in ET
are driven by a combination of energy and water availability, as neither
rainfall nor radiation alone could explain patterns in ET. In southern
basins, despite seasonal rainfall deficits, deep root water uptake allows
increasing rates of ET during the dry season, when radiation is usually
higher than in the wet season. We demonstrate contrasting ET seasonality with
satellite greenness across Amazon forests, with strong asynchronous
relationships in ever-wet watersheds, and positive correlations observed in
seasonally dry watersheds. Finally, we compared our results with estimates
obtained by two ET models, and we conclude that neither of the two tested
models could provide a consistent representation of ET seasonal patterns
across the Amazon. |
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| ISSN: | 2190-4979 2190-4987 |