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Title: SURFACE FLUX ESTIMATION USING RADIOMETRIC TEMPERATURE; A DUAL-TEMPERATURE-DIFFERENCE METHOD TO MINIMIZE MEASUREMENT ERROR

Author
item NORMAN, JOHN - UNIVERSITY OF WISCONSIN
item Kustas, William - Bill
item Prueger, John
item DIAK, GEORGE - UNIVERSITY OF WISCONSIN

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2000
Publication Date: 8/29/2000
Citation: N/A

Interpretive Summary: Surface temperature serves as a key boundary condition that defines the partitioning of surface radiation into sensible and latent heat fluxes. Surface brightness temperature measurements from satellites offer the unique possibility of mapping evapotranspiration at regional scales. Because uncertainties in satellite measurements of surface radiometric temperature a number of studies have found significant discrepancies between modeled and measured heat fluxes when using radiometric temperature. Recent research efforts have overcome these uncertainties. The major remaining obstacle to using satellite data for regional heat flux estimation is inadequate density of near-surface air temperature observations. In this paper we describe a simple, operational, double-difference approach for relating surface sensible heat flux to remote observations of surface brightness temperature, vegetative cover and dtype, and measurements of near-surface wind speed and air temperature from the synoptic weather network. A double difference of the time rate of change in radiometric and air temperature observations is related to heat flux. This double-difference approach reduces both the errors associated with deriving a radiometric temperature and defining meteorological quantities at large scales. This scheme is shown to have operational capabilities using satellite data; thus it has potential in providing regional scale assessment of evapotranspiration. This information would greatly enhance techniques for estimating crop yield and for assessing vegetation stress on a regional basis, ultimately improving agricultural management decisions.

Technical Abstract: Surface temperature serves as a key boundary condition that defines the partitioning of surface radiation into sensible and latent heat fluxes. Surface brightness temperature measurements from satellites offer the unique possibility of mapping surface heat fluxes at regional scales. Because uncertainties in satellite measurements of surface radiometric temperature a number of studies have found significant discrepancies between modeled and measured heat fluxes when using radiometric temperature. Recent research efforts have overcome these uncertainties and in addition have accounted for the difference between radiometric and aerodynamic temperature by considering soil and vegetative-canopy aerodynamic resistances. The major remaining obstacle to using satellite data for regional heat flux estimation is inadequate density of near-surface air temperature observations. In this paper we describe a simple, operational, double-difference approach for relating surface sensible heat flux to remote observations of surface brightness temperature, vegetative cover and type, and measurements of near-surface wind speed and air temperature from the synoptic weather network. A double difference of the time rate of change in radiometric and air temperature observations is related to heat flux. This double-difference approach reduces both the errors associated with deriving a radiometric temperature and defining meteorological quantities at large scales. The utility of this scheme is tested with ground-based radiometric temperature observations from several arid and sub-humid climates with a wide range of vegetative cover and meteorological conditions.