Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil...
Transcript of Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil...
![Page 1: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/1.jpg)
Improved Soil Moisture Variability in CLM 3.5
Sean SwensonNCAR Advanced Study Program
in collaboration with Keith Oleson and David Lawrence
![Page 2: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/2.jpg)
Outline
• Simulating soil moisture in Illinois with validation by Illinois State Water Survey observations.• Simulation of a site in Brazil (ABRACOS).• Incorporating the water table into the soil water equations.• Recommendations.• Current and Future work.
![Page 3: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/3.jpg)
Red: shallowest layerBlue: deepest layer
•Control shows most variability at depth.
•Observations show most variability near the surface.
Water table is not apparent in observed soil moisture data.
![Page 4: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/4.jpg)
Decreasing the f parameter (Q e(f∙z)) causes equilibrium baseflow to occur at greater depth, pushing the water table below 2 meters.
Variability is roughly uniform with depth.
![Page 5: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/5.jpg)
Decreasing the saturated hydraulic conductivity by an order of magnitude reproduces the phase lag with depth.
This increases variability, especially near the surface.
![Page 6: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/6.jpg)
Insolation is increased by 10% to match climatological values from other studies.
This is likely due to the linear interpolation currently used, which results in a poor diurnal cycle.
![Page 7: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/7.jpg)
The upper 10 cm of the observations exhibit anomalously wet conditions during the winter.
This can be modeled by a “compacted” layer by increasing the ratio of clay to sand.
This increases field capacity and decreases infiltration, further increasing variability near the surface.
![Page 8: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/8.jpg)
Finally, increasing Leaf Area Index (LAI) to 4 boosts transpiration.
The final simulation shows similar variability that is consistent with the observations in both amplitude, phase, and depth dependence.
The water table in this simulation is at a depth of about 3.5 meters.
![Page 9: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/9.jpg)
Outline
• Simulating soil moisture in Illinois with validation by Illinois State Water Survey observations.• Simulation of a site in Brazil (ABRACOS).• Incorporating the water table into the soil water equations.• Recommendations.• Current and Future work.
![Page 10: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/10.jpg)
Other sites: Brazil/ABRACOS/Reserva Jaru Forest Flux Tower
Control shows high soil wetness due to shallow water table.
New simulation is also wet, but due to high infiltration rates. Water table is much deeper, 68 meters.
![Page 11: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/11.jpg)
Outline
• Simulating soil moisture in Illinois with validation by Illinois State Water Survey observations.• Simulation of a site in Brazil (ABRACOS).• Incorporating the water table into the soil water equations.• Recommendations.• Current and Future work.
![Page 12: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/12.jpg)
The current water table formulation can exhibit pathological behavior.
The hydraulic conductivity used in the QCHARGE calculation is too low. During drying events, the water table fails to track the saturated contours.
Using a hydraulic conductivity based on the average soil moisture between the water table and the layer above it causes the water table to better track the saturated contours.
![Page 13: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/13.jpg)
“Fixing” the QCHARGE calculation reveals a second problem.
The “twostep” aquifer formulation decouples the flux of water from the soil column to the aquifer. This can result in unrealistic drying at depth.
Incorporating the water table as the lower boundary condition in the soil water equations leads to a consistent QCHARGE calculation, and eliminates these drying events.
![Page 14: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/14.jpg)
Outline
• Simulating soil moisture in Illinois with validation by Illinois State Water Survey observations.• Simulation of a site in Brazil (ABRACOS).• Incorporating the water table into the soil water equations.
• Recommendations.• Current and Future work.
![Page 15: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/15.jpg)
Summary & Recommendations
CLM 3.5 is demonstrated to possess the ability to simulate soil moisture observations with great detail.
Significant improvements to the simulation of soil moisture variability in CLM 3.5 can be obtained by a model formulation change combined with parameter calibration:
• Incorporate the exchange of water between the soil column and the aquifer (QCHARGE) into the soil water equations.
• Correct the hydraulic conductivity used to compute QCHARGE.
• Deepen the water table, by adjusting parameters controlling baseflow.
• Reexamine the values of saturated hydraulic conductivity (KSAT).
![Page 16: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/16.jpg)
Outline
• Simulating soil moisture in Illinois with validation by Illinois State Water Survey observations.• Simulation of a site in Brazil (ABRACOS).• Incorporating the water table into the soil water equations.• Recommendations.• Current and Future work.
![Page 17: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/17.jpg)
Current and Future Work
• Model calibration:
• are global parameter values adequate?
• can regional parameter values be determined?
• what is the appropriate ratio of surface runoff to baseflow?
• deepening the water table will further reduce surface runoff.
• Model validation:
• use combined constraints of GRACE and river discharge.
• use flux tower observations.
• obtain additional soil moisture and well level observations.
![Page 18: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/18.jpg)
![Page 19: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/19.jpg)
Deepening the Water Table
• f versus rtop_max (q ~ rtop_maxexp(fzwt):
• both deepen the water table by increasing drainage for a given depth
• increasing f dampens the variability, increasing rtop_max does not
![Page 20: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/20.jpg)
Deepening the Water Table
![Page 21: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/21.jpg)
Deepening the Water Table
![Page 22: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/22.jpg)
Deepening the Water Table
![Page 23: Improved Soil Moisture Variability in CLM 3.5 Sean Swenson … · 2009-02-13 · Improved Soil Moisture Variability in CLM 3.5 Sean Swenson NCAR Advanced Study Program in collaboration](https://reader035.fdocuments.in/reader035/viewer/2022081402/5f1d4189564acc698550c297/html5/thumbnails/23.jpg)
Partitioning Runoff
• in the topmodel formulation, surface runoff is a function of water table depth
• deepening the water table will further decrease surface runoff, and increase baseflow