1 Xiaoyan Jiang, Guo-Yue Niu and Zong- Liang Yang The Jackson School of Geosciences The University of Texas at Austin 03/20/2007 Feedback between the atmosphere, vegetation and groundwater represented in WRF/Noah Offline validation of soil moisture with Illinois data Coupled WRF/Noah simulations of rainfall in central U.S.
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Xiaoyan Jiang, Guo-Yue Niu and Zong-Liang Yang The Jackson School of Geosciences
Feedback between the atmosphere, vegetation and groundwater represented in WRF/Noah. Offline validation of soil moisture with Illinois data Coupled WRF/Noah simulations of rainfall in central U.S. Xiaoyan Jiang, Guo-Yue Niu and Zong-Liang Yang The Jackson School of Geosciences - PowerPoint PPT Presentation
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Xiaoyan Jiang, Guo-Yue Niu and Zong-Liang YangThe Jackson School of GeosciencesThe University of Texas at Austin
03/20/2007
Feedback between the atmosphere, vegetation and groundwater
represented in WRF/Noah
Offline validation of soil moisture with Illinois data
Coupled WRF/Noah simulations of rainfall in central U.S.
Offline validation of soil moisture with Illinois data(at two stations; daily from 1/1/1998 to 12/31/2002)
• Noah + DVGW produces a much wetter soil than the default Noah.
• DVGW reduces the amplitude of temporal variations.
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IntroductionObjectivesHypothesisLand cover and hydrogeological characteristics
over the Central U.S.Model descriptionExperiment designSimulation results and discussionsConclusions
The Impacts of Vegetation and Groundwater The Impacts of Vegetation and Groundwater Dynamics on North American Warm Season Dynamics on North American Warm Season
Precipitation over the Central U.S.Precipitation over the Central U.S.
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Understand the role of vegetation growth and groundwater dynamics in land-atmosphere interaction.
Improve the prediction of warm season precipitation in a coupled land-atmosphere model.
Identify the high-impact locations (Local or regional?).
Account for the role of initialization in intra-seasonal forecasting through ensemble simulations.
ObjectivesObjectives
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HypothesisRepresenting interactive canopy (or vegetation growth) and groundwater dynamics in a coupled land surface and atmospheric model improves seasonal precipitation.
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Study domain
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Land cover and hydrogeological characteristics over the Central U.S.
Dominant land cover types over the Central U.S. Aquifer distribution from Atlas
8Dickinson, R. E., M. Shaikh, R. Bryant, et al., 1998
Niu, G.-Y., Z.-L. Yang, R.E. Dickinson, L.E. Gulden, and H. Su, 2007
A Coupled Land-Atmosphere Model SystemA Coupled Land-Atmosphere Model System
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Model configurations The version 2.1.2 of the Weather Research and Forecasting model
(WRF) with time-varying sea surface temperatures.
Physics options and input data:• Lin et al. microphysics scheme;• Kain-Fritsch cumulus parameterization scheme;• Yonsei University Planetary boundary layer;• A simple cloud interactive radiation scheme;• Rapid Radiative Transfer Model longwave radiation scheme
A dynamic vegetation model of Dickinson et al. (1998) in Noah LSM. A simple groundwater model (SIMGM) (Niu et al. 2006) in Noah
LSM. NCEP-NARR reanalysis data. The model domain covers the whole continental U.S. and the grid
spacing is 32 km
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Ensemble experiments with WRFEnsemble experiments with WRF
Lifting condensation level as a function of soil moisture index
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ConclusionsConclusions The WRF/Noah model with augmented vegetation and
groundwater dynamics can improve the simulation of summertime precipitation over the Central U.S.
The increased precipitation (by 65%) corresponds to the increased latent heat flux (by 34%).
In summer, precipitation in the Central U.S. mostly comes from local evapotranspiration, showing strong land–atmosphere coupling.
The role of vegetation is significant (by 37%) in the grassland and cropland areas in summer.
Groundwater has impacts (by 16%) on summer precipitation in the transition zone.
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Conclusions (Cont)Conclusions (Cont)
• Throughout the day, precipitation is increased (improved) when vegetation dynamics is included, and it is further increased (improved) when groundwater dynamics is added. These increases are consistent with higher (lower) latent (sensible) heat fluxes.
• The increased precipitation with the Noah enhancements are also consistent with reduced lifting condensation levels, suggesting a positive soil moisture-precipitation feedback (wetter soil, more evapotranspiration, lower lifting condensation levels, and higher rainfall).
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Thanks for your attention!
Questions and suggestions?Questions and suggestions?