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Estimation of Spatial and Temporal Changes in Land Surface - - PowerPoint PPT Presentation

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Estimation of Spatial and Temporal Changes in Land Surface Emissivity to Improve Modeling of Evapotranspiration Andrew N. French 1 , Anand K. Inamdar 1 , Tom Schmugge 2 , Kenta Ogawa 3 , Frederic Jacob 4 1.USDA/ARS, Maricopa, Arizona, USA 2.New

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Estimation of Spatial and Temporal Changes in Land Surface Emissivity to Improve Modeling of Evapotranspiration

Andrew N. French1, Anand K. Inamdar1, Tom Schmugge2, Kenta Ogawa3, Frederic Jacob4

1.USDA/ARS, Maricopa, Arizona, USA 2.New Mexico State University, Las Cruces, NM 3.Hokkaido University, Sapporo, Japan 4.UMR LISAH‐SupAgro /INRA/IR

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Jornada Gulf of California

Emissivity Heterogeneity

  • ver the Southwestern USA

Rn - G = H + LE

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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NDVI for Jornada & Rio Grande 2001-2003

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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ASTER & MODIS Thermal Band Responses

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Effect of Emissivity on Land Surface Temperature

Errors in estimated emissivity can result in LST retrieval errors of 2-3 C Depending upon resistance term, these errors can exceed 50 W/m^2

a p r

T c H Δ = ρ

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Effect of Emissivity upon Land Cover Classification Can determine estimation of surface resistance

  • Distinguish between bare soil and

senescent vegetation

  • Better estimation of canopy geometry &

canopy height

  • Improve estimation of r_a and r_s

8 h zM =

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Effect of Emissivity on Net Longwave Flux

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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50 km

ASTER Composite over Jornada 2001-2003

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Short Wavelength TIR with ASTER/MODIS Jornada 2003

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Linear Broadband Emissivity Trend 21 ASTER scenes, 2001-2003 Small Changes: < 1%/year

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Coefficient of Determination (R2): 0.55 to 0.85

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Change Verification: LAI & Emissivity 2001-2003

LAI Emissivity

Qualitative support for trend Sites are not in trend core Decrease from 0.955 to 0.945, then flat or recovery

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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MODIS/Terra ASTER

Emissivity Changes Observed by ASTER & MODIS

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Explanations for Observed Emissivity Trends

Systematic TIR calibration errors. Systematic atmospheric correction errors. Long term changes in soil emissivities. Long term changes in vegetation canopy densities.

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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KS OK MODIS Emissivities (Band 29) SGP September 2007

Winter Wheat

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Temporal Emissivity vs. Vegetation Index

NDVI Emissivity (Band 29)

Winter Wheat in Southern Great Plains 2007

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Some Agricultural Regions Show Negligible Seasonal Change in Emissivity

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Winter Wheat Grazingland

NDVI NDVI

Emissivity

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Broadband Emissivity vs. NDVI

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Effect of Spatial Resolution on NDVI

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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Conclusions

  • Temporal changes in Land Surface Emissivity occur at

daily, seasonal, & inter-annual time scales.

– Depends on vegetation type & background soil.

  • The changes reflect change in vegetation canopy &

soil moisture.

  • NDVI cannot monitor non-green fraction, thus

emissivity data are complementary observations.

  • Emissivity changes impact ET estimation:

– Land Surface Temperature – Land Cover Type – Stage of Growth

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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NDVI:Information Loss with Resolution

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009

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ASTER & MODIS Thermal Band Responses

USDA ARS Pacific West Area Remote Sensing Workshop 29 April 2009