The GLACE-Hydrology Experiment: Effects of Land-Atmosphere Coupling on Soil Moisture Variability and Drought Predictability
Abstract
What impact does land-atmosphere coupling have on land variability? We investigate this question using a new two-step climate model experiment design named the "GLACE-Hydrology" experiment. In the first step, the experiment generates two ensemble climate forcing by a control ensemble of a coupled land-atmosphere climate model (CAM5-CLM4.5, 'land-atmosphere coupled') and a second ensemble configured identically, except that the land-atmosphere coupling is strongly dampened through prescription of the control model's seasonally-evolving soil moisture climatology ('land-atmosphere uncoupled'), similar to the GLACE-CMIP5 experiment. In the second step, land-only ensemble simulations, forced with the climate forcing data from the 'coupled' and 'uncoupled' forcing scenarios are performed. This allows investigation of the soil moisture variability under the two forcing scenarios. We find that the land-atmosphere coupling significantly increases the soil moisture variability in the mid-latitude region and in the boreal summer. We decomposed the total soil moisture variability change into contributions by the four driver climate processes: soil moisture memory, precipitation forcing, soil moisture-evapotranspiration coupling, and soil moisture-runoff coupling. We attribute the increased soil moisture variability to a significantly higher soil moisture memory due to the land-atmosphere coupling. In the case of the 2012 US Great Plains drought, 85% of the observed soil moisture anomalies is captured by the coupled experiment which shows a statistically significant skill; whereas the uncoupled experiment does not show a significant skill. Overall, this study hypothesizes that land-atmosphere coupling can play an equally important role as the sea surface temperature anomalies during a major drought event.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H54G..06K
- Keywords:
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- 1833 Hydroclimatology;
- HYDROLOGY;
- 1840 Hydrometeorology;
- HYDROLOGY;
- 1843 Land/atmosphere interactions;
- HYDROLOGY;
- 1866 Soil moisture;
- HYDROLOGY