Impact of Earth greening on the terrestrial water cycle

Impact of Earth greening on the terrestrial water cycle AbstractLeaf area index (LAI) is increasing throughout the globe, implying the Earth greening. Global modelling studies support this contention, yet satellite observations and model simulations have never been directly compared. Here, for the first time, we used a coupled land-climate model to quantify the potential impact of the satellite-observed Earth greening over the past 30 years on the terrestrial water cycle. The global LAI enhancement by 8% between the early 1980s and the early 2010s is modelled to have caused increases of 12.0 ±2.4 mm yr-1 in evapotranspiration and 12.1 ±2.7 mm yr-1 in precipitation — about 55 ±25% and 28 ±6% of the observed increases in land evapotranspiration and precipitation, respectively. In wet regions, the greening did not significantly decrease runoff and soil moisture because it intensified moisture recycling through a coincident increase of evapotranspiration and precipitation. But in dry regions including Sahel, West Asia, northern India, western United States and the Mediterranean coast, the greening was modelled to significantly decrease soil moisture through its coupling with the atmospheric water cycle. This modelled soil moisture response, however, might have biases due to the precipitation biases in the model. For example, the model dry bias might have underestimated soil moisture response in the observed dry area (e.g. Sahel and northern India) given that the modelled soil moisture is near the wilting point. Thus an accurate representation of precipitation and its feedbacks in Earth system models is essential for simulations and predictions of how soil moisture responds to LAI changes and therefore how the terrestrial water cycle responds to climate change. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

Impact of Earth greening on the terrestrial water cycle

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0442
D.O.I.
10.1175/JCLI-D-17-0236.1
Publisher site
See Article on Publisher Site

Abstract

AbstractLeaf area index (LAI) is increasing throughout the globe, implying the Earth greening. Global modelling studies support this contention, yet satellite observations and model simulations have never been directly compared. Here, for the first time, we used a coupled land-climate model to quantify the potential impact of the satellite-observed Earth greening over the past 30 years on the terrestrial water cycle. The global LAI enhancement by 8% between the early 1980s and the early 2010s is modelled to have caused increases of 12.0 ±2.4 mm yr-1 in evapotranspiration and 12.1 ±2.7 mm yr-1 in precipitation — about 55 ±25% and 28 ±6% of the observed increases in land evapotranspiration and precipitation, respectively. In wet regions, the greening did not significantly decrease runoff and soil moisture because it intensified moisture recycling through a coincident increase of evapotranspiration and precipitation. But in dry regions including Sahel, West Asia, northern India, western United States and the Mediterranean coast, the greening was modelled to significantly decrease soil moisture through its coupling with the atmospheric water cycle. This modelled soil moisture response, however, might have biases due to the precipitation biases in the model. For example, the model dry bias might have underestimated soil moisture response in the observed dry area (e.g. Sahel and northern India) given that the modelled soil moisture is near the wilting point. Thus an accurate representation of precipitation and its feedbacks in Earth system models is essential for simulations and predictions of how soil moisture responds to LAI changes and therefore how the terrestrial water cycle responds to climate change.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Jan 11, 2018

References

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