Representing nighttime and minimum conductance in CLM4.5: global hydrology and carbon sensitivity analysis using observational constraints
The terrestrial biosphere regulates climate through carbon, water, and energy exchanges with the atmosphere. Land-surface models estimate plant transpiration, which is actively regulated by stomatal pores, and provide projections essential for understanding Earth's carbon and water resources. E...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-01-01
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| Series: | Geoscientific Model Development |
| Online Access: | http://www.geosci-model-dev.net/10/321/2017/gmd-10-321-2017.pdf |
| Summary: | The terrestrial biosphere regulates climate through carbon, water, and
energy exchanges with the atmosphere. Land-surface models estimate plant
transpiration, which is actively regulated by stomatal pores, and provide
projections essential for understanding Earth's carbon and water resources.
Empirical evidence from 204 species suggests that significant amounts of
water are lost through leaves at night, though land-surface models typically
reduce stomatal conductance to nearly zero at night. Here, we test the
sensitivity of carbon and water budgets in a global land-surface model, the
Community Land Model (CLM) version 4.5, to three different methods of
incorporating observed nighttime stomatal conductance values. We find that
our modifications increase transpiration by up to 5 % globally, reduce
modeled available soil moisture by up to 50 % in semi-arid regions, and
increase the importance of the land surface in modulating energy fluxes.
Carbon gain declines by up to ∼ 4 % globally and > 25 % in semi-arid regions. We advocate for realistic constraints of
minimum stomatal conductance in future climate simulations, and widespread
field observations to improve parameterizations. |
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| ISSN: | 1991-959X 1991-9603 |