Variation of Surface Soil Moisture Variation of Surface Soil Moisture and its Implications Under and its Implications Under

Changing Climate ConditionsChanging Climate Conditions

Variation of Surface Soil Moisture Variation of Surface Soil Moisture and its Implications Under and its Implications Under

Changing Climate ConditionsChanging Climate Conditions

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Outline:Outline: Motivation

Importance

Study Region

Methodology

Results

Conclusions

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MotivationMotivationProblem

Statement:

Surface soil Moisture is highly variable in space and time and often difficult to predict using LSMs

Linkage:

Global climate models need accurate initial and boundary conditions for better prediction and forecasting

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Motions and disturbances of atmospheric fluid are influenced by differential heating and friction at the surface

Differential heating, radiative cooling, turbulent flux and thermal radiation all the processes strongly controlled by availability of soil moisture

Control evapotranspiration and partitioning of latent and sensible heat fluxes

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Study Region: (Illinois & Study Region: (Illinois & Indiana)Indiana)

19 sites in Illinois

Soil Moisture data at 10 cm depth ( Global soil Moisture Data Bank (Robock et al, 2000)

Climate Variables : Precip, Air temp., Soil Temp., Solar Radiation, Potential ET ( Illinois Climate Network (ICN)

Soil Type: Silt Loam, silt clay loam

11 sites in Indiana Soil temperature data

Monthly Stream Flow

Data from USGS for 5 gauging stations

Latent Heat Flux Data

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AmeriFlux Sites

Objectives:Objectives:Objectives:Objectives:

To improve surface soil moisture simulation with Variable Infiltration Capacity (VIC) model using multi-variable evaluation with observed data

To study the impact of projected future climate on soil moisture and its interaction with land surface variables

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Annual anomalies and soil Annual anomalies and soil moisturemoisture

Annual anomalies show good relationship with soil moisture anomaly

_____ Soil Moisture______ Precipitation.______ Air Temperature______ Potential Evapotranspiration

Observed Data

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Monthly Stream flow Monthly Stream flow SimulationSimulation

Calibration Period (1980 -1990)

Validation Period (1991 -2005) Total Period (1980-2005) ------- Observed ------- SimulatedNash-Sutcliffe Eff. (0.6-

0.7)

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Solar Radiation SimulationsSolar Radiation Simulations

VIC model predicts solar radiation in a good agreement with observation

The over prediction for spring season

It may influence spring season soil moisture dynamics

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-------- Obs.-------- Sim.

Soil Temperature Simulation (10 Soil Temperature Simulation (10 cm)cm) Soil Temperature

effects long wave radiation, sensible and ground heat flux

There is a good agreement between simulated and observed soil temperature, however model under predicts summer soil temperature

-------- Obs.-------- Sim

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Soil Temperature Simulations in Indiana Soil Temperature Simulations in Indiana (10 cm)(10 cm)

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-------- Obs.-------- Sim The under

prediction is more in summer than winter

It will influence summer ET, soil temperature and therefore soil moisture

Latent Heat Flux Latent Heat Flux SimulationsSimulations

Observed data from Ameriflux network

3 Sites in Illinois and Indiana

Might be land use effect

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Model captures less temporal variability than observed soil moisture

Over prediction in summer might be due to under prediction of solar radiation and soil temperature

Site no -11: outwash plains

Site no – 12 : poorly drained soil on knoll

Site no -34: Gravely loamy sand

Soil Moisture Simulation (0-10 cm)Soil Moisture Simulation (0-10 cm)

------ Obs.------- Sim.

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Simulated monthly anomaly of soil moisture shows less persistence

Soil Moisture Persistence (Obs. Vs Soil Moisture Persistence (Obs. Vs Sim.)Sim.)

------ Obs.------ Sim.

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Overall Model Performance for 16 Overall Model Performance for 16 sitessites((Monthly Time ScaleMonthly Time Scale))

Coefficient of variation for simulated soil moisture is under predicted

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Soil Moisture Interaction Soil Moisture Interaction (Avg. of 16 sites)(Avg. of 16 sites)Annual soil

moisture anomalies have strong correlation with sensible and latent heat fluxes anomalies

Simulation Period ( 1917-2006)

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Projected Change (Projected Change (PCM.A1 (2070-2099) PCM.A1 (2070-2099) – Observed Forcing (1917-2006) )– Observed Forcing (1917-2006) )

Seasonal Average Fluxes Annual Average Fluxes

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Projected Climate Impact on Land Projected Climate Impact on Land Surface Variables (Avg. of 16 sites)Surface Variables (Avg. of 16 sites)

IPCC AR3 Climate model output (PCM, HadCM3, GFDL)

Scenarios: A1, B1 and SresA1F1, SersB1

____Observed (1917-2006)

___ GFDL (2070-2099)___ PCM (2070 -2099)____HadCM3 (2070-2099)Projections: Decrease

in soil moisture – increase in soil temp- increase in ET- increase in LHF- decrease in SHF

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Conclusions:Conclusions:VIC model simulates surface soil moisture,

soil temperature and other variables which are in good agreement with observations

Soil moisture anomalies of observed data show good correlation with other climatic variables

Climate model projections show decrease in soil moisture, increase in ET, increase in ST which might lead to significant changes in energy fluxes

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