Atmospheric Radiation Balance Over Alfalfa

by Gail E. Bingham,
Esmaiel Malek,

Document Type: Proceeding Paper

Part of: Management of Irrigation and Drainage Systems: Integrated Perspectives


An experiment was carried out in an alfalfa field in Logan, Utah, U.S.A., during 8-12 September 1992, to evaluate methods and expected accuracy of continuous radiation balance component determination in mountainous terrain. Four different types of pyranometers were used to evaluate the measurement of incoming solar radiation (Rsi). An inverted pyranometer was employed to measure the reflected (outgoing) solar radiation (Rso). Two Q-6 net radiometers measured the net radiation (Rn). Three pyrgeometers were used to measure the incoming longwave (atmospheric) radiation (Rli). An infrared thermometer were used to measure the crop surface temperature (Tc). The radiation balance was calculated and compared with the measured net radiation. Statistical analysis showed that, while good overall agreement between the two methods was observed, slight differences occurred between pyrgeometers. The multiple sensor exercise proved fruitful in demonstrating likely calibration errors, while the technique provided value in data quality assurance. Incoming longwave radiation was slightly different from standard estimation techniques.

Subject Headings: Radiation | Vegetation | Temperature measurement | Measuring instruments | Solar radiation | Field tests | Mountains | Terrain | Utah | United States

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