Spectral differences in glass and perspex thermopile shields and the effects on solar radiation measurements
✍ Scribed by H.H. Bosman
- Publisher
- Elsevier Science
- Year
- 1983
- Weight
- 493 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0002-1571
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✦ Synopsis
Bosman, H.H., 1983
. Spectral differences in glass and perspex thermopile shields and the effects on solar radiation measurements. Agric. Meteorol., 28: 65--74.
Anomalies in shortwave and net solar radiation results recorded with solarimeters and perspex shielded pyrradiometers, were investigated. A spectrophotographic analysis showed that glass transmitted 17% more light than perspex over the wave lengths 280--4600 nm. On days with clear skies in spring, glass shielded solarimeters recorded 16.6% higher solar radiation than modified pyrradiometers with perspex shielded thermopiles. The net shortwave radiation measured during the same periods was 26.8% lower than that calculated from solarimeters. Unless proper double glass hemispheres are available to convert all wave pyrradiometers to shortwave radiometers, it would be advisable to use double glass hemisphered solarimeters to record solar radiation. Perspex, therefore, cannot be regarded as a substitute for the superior quality of glass hemispheres in shortwave thermopile shields and for longwave filter material.