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 Remote sensing of evapotranspiration using automated calibration: development and testing in the state of Florida.

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Type of Resource: text

Genre: Electronic Thesis or Dissertation

Issuance: single unit

Date Created: Summer 2014

Date Issued: 2014

Publisher: Florida Atlantic University

Physical Form: Online Resource

Extent: 293 p.

Language(s): English

Summary: Thermal remote sensing is a powerful tool for measuring the spatial variability ofevapotranspiration due to the cooling effect of vaporization. The residual method is apopular technique which calculates evapotranspiration by subtracting sensible heat fromavailable energy. Estimating sensible heat requires aerodynamic surface temperaturewhich is difficult to retrieve accurately. Methods such as SEBAL/METRIC correct forthis problem by calibrating the relationship between sensible heat and retrieved surfacetemperature. Disadvantage of these calibrations are 1) user must manually identifyextremely dry and wet pixels in image 2) each calibration is only applicable over limitedspatial extent. Producing larger maps is operationally limited due to time required tomanually calibrate multiple spatial extents over multiple days. This dissertation developstechniques which automatically detect dry and wet pixels. LANDSAT imagery is usedbecause it resolves dry pixels. Calibrations using 1) only dry pixels and 2) including wetpixels are developed. Snapshots of retrieved evaporative fraction and actual evapotranspiration are compared to eddy covariance measurements for five study areas inFlorida: 1) Big Cypress 2) Disney Wilderness 3) Everglades 4) near Gainesville, FL. 5)Kennedy Space Center. The sensitivity of evaporative fraction to temperature, availableenergy, roughness length and wind speed is tested. A technique for temporallyinterpolating evapotranspiration by fusing LANDSAT and MODIS is developed andtested.The automated algorithm is successful at detecting wet and dry pixels (if theyexist). Including wet pixels in calibration and assuming constant atmosphericconductance significantly improved results for all but Big Cypress and Gainesville.Evaporative fraction is not very sensitive to instantaneous available energy but it issensitive to temperature when wet pixels are included because temperature is required forestimating wet pixel evapotranspiration. Data fusion techniques only slightlyoutperformed linear interpolation. Eddy covariance comparison and temporalinterpolation produced acceptable bias error for most cases suggesting automatedcalibration and interpolation could be used to predict monthly or annual ET. Mapsdemonstrating spatial patterns of evapotranspiration at field scale were successfullyproduced, but only for limited spatial extents. A framework has been established forproducing larger maps by creating a mosaic of smaller individual maps.

Identifier: FA00004194 (IID)

Note(s): Includes bibliography.Dissertation (Ph.D.)--Florida Atlantic University, 2014.

Subject(s): Climatic changesEnvironmental sciences -- Remote sensingEvapotranspiration -- MeasurementGeographic information systemsRemote sensing -- Data processingSpatial analysis (Mathematics)

Held by: Florida Atlantic University Digital Library

Sublocation: Boca Raton, Fla.

Persistent Link to This Record:

Restrictions on Access: All rights reserved by the source institution

Owner Institution: FAU

Autor: Evans, Aaron H., author Obeysekera, Jayantha Dr., Thesis advisor Zhang, Caiyun Dr., Thesis advisor Charles E. Schmidt College of



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