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Evapotranspiration partitioning in CMIP5 models: Uncertainties and future projections

Evapotranspiration partitioning in CMIP5 models: Uncertainties and future projections
Evapotranspiration partitioning in CMIP5 models: Uncertainties and future projections
Evapotranspiration (ET) is a key process affecting terrestrial hydroclimate, as it modulates the land surface carbon, energy, and water budgets. Evapotranspiration mainly consists of the sum of three components: plant transpiration, soil evaporation, and canopy interception. Here we investigate how the partitioning of ET into these three main components is represented in CMIP5 model simulations of present and future climate. A large spread exists between models in the simulated mean present-day partitioning; even the ranking of the different components in the global mean differs between models. Differences in the simulation of the vegetation leaf area index appear to be an important cause of this spread. Although ET partitioning is not accurately known globally, existing global estimates suggest that CMIP5 models generally underestimate the relative contribution of transpiration. Differences in ET partitioning lead to differences in climate characteristics over land, such as land–atmosphere fluxes and near-surface air temperature. On the other hand, CMIP5 models simulate robust patterns of future changes in ET partitioning under global warming, notably a marked contrast between decreased transpiration and increased soil evaporation in the tropics, whereas transpiration and evaporation both increase at higher latitudes and both decrease in the dry subtropics. Idealized CMIP5 simulations from a subset of models show that the decrease in transpiration in the tropics largely reflects the stomatal closure effect of increased atmospheric CO2 on plants (despite increased vegetation from CO2 fertilization), whereas changes at higher latitudes are dominated by radiative CO2 effects, with warming and increased precipitation leading to vegetation increase and simultaneous (absolute) increases in all three ET components.
0894-8755
2653-2671
Berg, Alexis
78bd0eda-314b-4474-bc3c-a4a8b3a4f2a4
Sheffield, Justin
dd66575b-a4dc-4190-ad95-df2d6aaaaa6b
Berg, Alexis
78bd0eda-314b-4474-bc3c-a4a8b3a4f2a4
Sheffield, Justin
dd66575b-a4dc-4190-ad95-df2d6aaaaa6b

Berg, Alexis and Sheffield, Justin (2019) Evapotranspiration partitioning in CMIP5 models: Uncertainties and future projections. Journal of Climate, 32 (10), 2653-2671. (doi:10.1175/JCLI-D-18-0583.1).

Record type: Article

Abstract

Evapotranspiration (ET) is a key process affecting terrestrial hydroclimate, as it modulates the land surface carbon, energy, and water budgets. Evapotranspiration mainly consists of the sum of three components: plant transpiration, soil evaporation, and canopy interception. Here we investigate how the partitioning of ET into these three main components is represented in CMIP5 model simulations of present and future climate. A large spread exists between models in the simulated mean present-day partitioning; even the ranking of the different components in the global mean differs between models. Differences in the simulation of the vegetation leaf area index appear to be an important cause of this spread. Although ET partitioning is not accurately known globally, existing global estimates suggest that CMIP5 models generally underestimate the relative contribution of transpiration. Differences in ET partitioning lead to differences in climate characteristics over land, such as land–atmosphere fluxes and near-surface air temperature. On the other hand, CMIP5 models simulate robust patterns of future changes in ET partitioning under global warming, notably a marked contrast between decreased transpiration and increased soil evaporation in the tropics, whereas transpiration and evaporation both increase at higher latitudes and both decrease in the dry subtropics. Idealized CMIP5 simulations from a subset of models show that the decrease in transpiration in the tropics largely reflects the stomatal closure effect of increased atmospheric CO2 on plants (despite increased vegetation from CO2 fertilization), whereas changes at higher latitudes are dominated by radiative CO2 effects, with warming and increased precipitation leading to vegetation increase and simultaneous (absolute) increases in all three ET components.

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e-pub ahead of print date: 24 April 2019
Published date: 1 May 2019

Identifiers

Local EPrints ID: 431053
URI: http://eprints.soton.ac.uk/id/eprint/431053
ISSN: 0894-8755
PURE UUID: 232b3711-5439-442d-82b5-9ac63185fc3a
ORCID for Justin Sheffield: ORCID iD orcid.org/0000-0003-2400-0630

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Date deposited: 22 May 2019 16:30
Last modified: 16 Mar 2024 04:23

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Author: Alexis Berg

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