Potential Soil Moisture Retrieval from Aquarius Instrument

Potential Soil Moisture Retrieval from Aquarius Instrument

Mississippi State UniversityGeosystems Research Institute

2NASA RPC Review (3/2/09)

Aquarius Evaluation Team & Collaborators

• MSU Team– Robert Moorhead– Xingang Fan– Valentine Anantharaj– Georgy Mostovoy– Graduate student (MSU GRI and ECE Dept.)

• External Team– GMU & CREW

• Partner Agencies– Garry Schaeffer (USDA NRCS)– Steve Hunter (United States Bureau of Reclamation)


Identified Decision Support Needs

• Routine analysis land surface state over the continental needs

watersoilssunweatherclimatevegetationterrain

observe, model, assimilate


Anticipated Societal Benefits

1. provides critical information to support drought monitoring and mitigation

2. provides essential information for predicting droughts based on weather and climate predictions

3. supports irrigation water management4. supports fire risk assessment5. supports water supply forecasting and NWS flood forecasting6. supplies a critical missing component to assist with snow, climate

and associated hydrometeorological data analysis7. supports climate change assessment8. enables water quality monitoring9. supports a wide variety of natural resource management & research

activities such as NASA remote sensing activities of soil moisture and ARS watershed studies.


Purpose of RPC Aquarius Experiments

• Evaluate feasibility and usefulness of Aquarius data for decision support in water resources management and other cross-cutting applications.

Approach:I. Aquarius Evaluation: Test, characterize, and evaluate

potential Aquarius soil moisture data via an OSSE.II. Downscaling for land surface modeling: Downscale

Aquarius data and evaluate by land surface modeling.III. Sensitivity Studies: Different LSM(s), input parameters


Experimental Objectives and Approach

• Using an OSSE, retrieve potential space-based soil moisture estimation using Aquarius radiometer and scatterometer.

• Generate moisture and energy fluxes at 10x10 km2 using a land surface model to assimilate the retrieved synthetic (simulated) soil moisture product.

• Evaluate experimental products for use in water management applications.

• Quantify uncertainties.


Identified Tasks

• Develop and finalize experimental design. (Otherwise mistake could be expensive to correct). This will particularly include strategies for nature run, emission and backscatter models, orbital and sensor model, selection of retrieval algorithms.

• Develop and validate nature run.• Retrieve soil moisture using the methodology outlined

later.• Compare with the benchmark data aggregated from the

NR. Quantify errors and uncertainties.• Document and publish results

NASA RPC Review (3/2/09) 10


Aquarius OSSE Design


Generalized OSSE Framework(Courtesy: JCSDA)

16

HYDROS OSSE Example

NASA RPC Review (3/2/09)


Aquarius OSSE: Experimental Design


Remote Sensing ConceptRadiative Transfer at the surface

Soil Surface

Vegetation Surface

Ts

Tb

Tsτc

T1

T3

T2

Tbp can be written as

Tbp = T1+T2+T3 T1,T2,T3 correspond to

contributions in the above equation

Ts = Soil temperature Tc = Vegetation temperature

τc = function of vegetation water content

esp and rsp are functions of soil water content

)exp(1)exp(11)exp( cspcpccspsbp rTeTT


1/8 deg domain size: 144x80 points 30.1875 – 40.0625 N, 107.8125 – 89.9375 WIf aggregated to 100km: 18x10points

1/8 deg Nature Run using LIS-CLM


Orbital Senor ModelingNature Run

Forward ModelingSoil Moisture Retrieval

Nature RunLIS modelCLM LSM

NLDAS Forcing1/8 deg

TOA (Satellite)Emission model

Radiometer/ Backscatter

1/8 deg

Satellite ObsOrbital modelRe-samplingAdding Noise

1 deg

RetrievalInversion modelRetrieved soil

moisture1 deg

Data assimilationLIS model

NOAH LSMCDAS + ENKF

1/8 deg

ValidationCompare to

“truth”

OSSE Flowchart (simplified)

Nature RunLIS CLM

NLDAS Forcing1/8 deg



1/8 deg


moisture1 deg


NOAH LSM + ENKF1/8 deg


“truth”

Nature Run Output of Soil moisture at 10 soil layers, hourly output from 2002-09-01 to 2003-10-311/8 deg resolution

Soil moisture of the top layer at 13 UTC 2002-09-01

Nature Run using LIS-CLM


1/8 deg



1/8 deg


moisture1 deg




“truth”

Forward Emission Output of Brightness Temperature (Tb)as can be seen from radiometer, and radar echo (Sigma) as from back scatterometer, a total of 15 maps each time point:Three look angles (29,38,45)Five variables: two Tb (h,v) and three simga (hh,hv,vv)

Tb(h) Tb(v)

sigma(hh) sigma(hv) sigma(vv)

Shown below are Tb(h), Tb(v), sigma(hh), sigma(hv), sigma(vv) from look angle 29 at 13 UTC 2002-09-01

Forward ModelingMicrowave Emissions and Backscatter

Orbital Sensor ModelingSimulation of Aquarius Footprints

Experiment Domain30.1875 – 40.0625 N, 107.8125 – 89.9375 W

Simulation of Aquarius Footprints

Radiometer ScatterometerParameter Inner

BeamMiddle Beam

Outer Beam

Inner Beam

Middle Beam

Outer Beam

Look Angle 25.8 33.8 40.3 25.9 33.9 40.3Azimuth Angle 9.8 -15.3 6.5 9.7 -15.3 6.5

Footprint Size (km) 89 x 80 113 x 88 150 x 106 68 x 60 85 x 67 113 x 80

• Satellite Tool Kit (STK 8.0) has been used for simulation of Aquarius Footprints

• Generated geodetic Latitude – Longitude contour line reports for re-sampling with the temperature data

Radiometer Footprint

Scatterometer Footprint


1/8 deg



1/8 deg

Orbital modelSatellite ObsRe-samplingAdding Noise

1 deg


moisture1 deg




“truth”

• Satellite Tool Kit (STK 8.0) has been used for simulation of Aquarius Footprints

• Generated geodetic Latitude – Longitude contour line reports for re-sampling with the temperature data

Radiometer Footprint

Scatterometer Footprint

FootprintsInner Beam : 94X76 kmMiddle Beam: 120X84 kmOuter Beam: 156X97 km


1/8 deg



1/8 deg


1 deg


moisture1 deg




“truth” Look angle 29 Look angle 38 Look angle 45

7-day Tb(h)

7-daySigma(hh)

Look angle 29 Look angle 38 Look angle 45 Noise

Gaussian noise of zero-mean and stdev equals 1K and 0.5 dB for Tb and sigma, respectively

Forward emission model output of Tb and sigma are re-sampled for the Aquarius footprints, and then aggregated to 1-degree resolution. The satellite has a 7-day revisit time period, so the following shows only one Tb and one sigma over a 7-day period, from three look angles.


1/8 deg



1/8 deg


1 deg


moisture1 deg




“truth”

Average of Tb(h) and Tb(v) retrievals

Average of sigma(hh), sigma(hv), and sigma(vv)

retrievals

Look angle

29

38

45

Retrieved soil moisture[from brightness temperature (Tb) & backscatter (sigma)]


Data Assimilation Experiments(Preliminary Results)


Soil moisture at a lightly-vegetated pixel(34.3125°N, 108.562°W )

TruthOpen Loop (No D/A)With Data Assimilation

Retrieved SM


Soil moisture at a heavily-vegetated pixel(34.3125°N, 94.5625°W )


Retrieved SM


Soil Moisture(domain averaged)


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Summary of Progress• Completed Tasks

– OSSE experimental design– Nature Run (synthetic truth)– Orbital Sensor Modeling and Simulations– Microwave Emissions and Backscatter Modeling– Soil moisture retrieval– Synthesis of experimental SM product– Assimilation of SM product using LIS EnKF (preliminary)

• Final Steps (in progress)– Validation of DA runs– Error analysis– Final evaluation (document and publish)

NASA RPC Review (3/2/09)


Contact Information

Valentine Anantharaj<[email protected]>

Tel: (662)325-5135

mailto:[email protected]

Potential Soil Moisture Retrieval from Aquarius Instrument

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