Improving vegetation response to drought stress in earth system models
Abstract
The exchange of carbon and water between land and atmosphere is regulated in part by photosynthesis. In the mid-latitudes, earth system models project an increase in photosynthesis to accompany rising atmospheric CO2 concentrations, warmer temperatures, and longer growing seasons, despite enhanced drought conditions in some regions. However, the land surface components of earth system models are known to poorly simulate plant response to drought and temperature stress. These plant responses are parameterized at the sub-grid cell level and the appropriate values in such parameterizations are often poorly constrained, leading to uncertainty in predictions of ecosystem response to changes in environmental conditions.
To better understand the sensitivity of vegetation response to parameter selection in an earth system model, we used a large perturbed physics ensemble and a suite of statistical emulators. We dynamically downscaled an ensemble of global climate (HadAM3p) simulations using a 25-km resolution regional climate model HadRM3p with the land-surface scheme MOSES2. We simultaneously perturbed land surface parameters relating to the exchange of carbon, water, and energy between the land surface and atmosphere. Statistical emulation was used as a computationally cost-effective tool to explore sensitivities and interactions. We explored sensitivity in relationship between soil moisture, vapor pressure deficit (VPD), and stomatal conductance and found that a number of parameters both directly and indirectly influence the modeled relationship. We utilized flux tower measurements to constrain the relationship and selected an ensemble of parameterizations that span the range of observational uncertainty. We evaluated the impact of improving the relationship between soil moisture, VPD, and stomatal conductance on variability in modeled net primary productivity. We found that modeled plant response to drought conditions can be substantially improved through adjusting model parameters without making structural changes. Appropriately capturing plant response to water and temperature stress will improve model projections of changes in the land-atmosphere exchange of carbon and water.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGC13G1117H
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGEDE: 1622 Earth system modeling;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGEDE: 1988 Temporal analysis and representation;
- INFORMATICS