Surface Temperature Variations Measured from an Airplane over Several Surface Types

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  • 1 University of Wisconsin
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Abstract

The problems and advantages of the bolometric method of measuring surface temperature from an airplane are discussed. It is shown that the airborne bolometer measures a weighted area-mean temperature which is a function of the surface temperature distribution and emissivity. For the employed wavelength of radiation (in the atmospheric “window”), the effect of atmospheric absorptivity is negligible under ordinary conditions for altitudes of 300 m or less, but can be an important consideration for flight levels above 300 m. From a series of flights over Southwestern Wisconsin it is concluded that the diurnal variation of surface temperature is greatest in flat farmland and sandy field areas, where a maximum difference of 29C occurred. Hilly woods and fields showed the smallest diurnal variation, with a maximum of 14C. The maximum standard deviation occurred in flat farmland area, with a value of 6C. A swampy area had a maximum value of 2C for a standard deviation.

Abstract

The problems and advantages of the bolometric method of measuring surface temperature from an airplane are discussed. It is shown that the airborne bolometer measures a weighted area-mean temperature which is a function of the surface temperature distribution and emissivity. For the employed wavelength of radiation (in the atmospheric “window”), the effect of atmospheric absorptivity is negligible under ordinary conditions for altitudes of 300 m or less, but can be an important consideration for flight levels above 300 m. From a series of flights over Southwestern Wisconsin it is concluded that the diurnal variation of surface temperature is greatest in flat farmland and sandy field areas, where a maximum difference of 29C occurred. Hilly woods and fields showed the smallest diurnal variation, with a maximum of 14C. The maximum standard deviation occurred in flat farmland area, with a value of 6C. A swampy area had a maximum value of 2C for a standard deviation.

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