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Significance of Fluctuations in Sky Radiant Emittance for Infrared Thermometry 1
Author(s) -
Idso Sherwood B.,
Jackson Ray D.
Publication year - 1968
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1968.00021962006000040017x
Subject(s) - thermal emittance , infrared , sky , radiant energy , optics , flux (metallurgy) , radiant flux , wavelength , environmental science , physics , remote sensing , materials science , astrophysics , radiation , beam (structure) , geology , metallurgy
A theoretical analysis of clear sky radiant emittance in the 600 to 1300 cm −1 waveband showed that this energy flux should be fairly constant over a diurnal period, contrary to some recently reported measurements. New experiments revealed this to be true and indicated that the source of error in the earlier work was due to equipment malfunction. The errors in radiometrically determined surface temperatures caused by neglecting the small variations which do occur were determined to be less than the limits of accuracy of present‐day infrared thermometers in many applications of infrared thermometry to soil and plant research. A nomogram predicted the temperature error to be expected from neglect of clear sky radiant emittance variations for surfaces with temperatures between 0 and 60 C and infrared emittances between 1.00 and 0.90.