Solar UV measurements at the Agricultural University of Norway Cecilia Futsaether and Arne Auen Grim

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Solar UV measurements at theAgricultural
University of NorwayCecilia Futsaether and Arne
Auen Grimnes, Dept. of Agricultural Engineering,
Agricultural University of Norway, N-1432 Ås,
Norway.
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Measurement overview

• A meteorological station was established at the
  Agricultural University of Norway at Ås (35 km
  south of Oslo) in 1870. The purpose of the
  station is to study the interaction between the
  weather/climate and agricultural production.
  During the early years, measurements were
  restricted to parameters such as air and soil
  temperature, humidity and wind velocity. Since
  approximately 1950, these measurements have been
  extended to include solar radiation. These
  meteorological data are currently used to develop
  weather forecasts which target agricultural
  activities such as irrigation and fertilizer and
  pesticide application.
• The station is located on a 1 hectar flat, grassy
  field. The grass is kept at a fairly constant
  length (5 cm) throughout the summer months. The
  instruments have been position such that
  interference (i.e. instrument shading) is
  avoided. No other obstacles (houses or trees) are
  located within 50 m of the perimeter of the
  field. A small area of the field is reserved for
  plant growth studies.

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The meteorological station
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Meteorological measurements
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Solar UV measurements

• Solar radiation measurements have been conducted
  since 1950. Broadband ultraviolet measurements
  were commenced in 1977 in conjunction with a
  joint research project between the five Nordic
  countries 1. The aim of the project was to
  chart the spectral distribution of solar
  radiation in the Nordic area in order to provide
  agronomists studying the effects of radiation on
  plant growth with data.
• Solar radiation (385-2800 nm) has since been
  measured using Eppley spectral pyranometers
  equipped with different glass filters. An Eppley
  TUVR radiometer which measures integrated
  irradiances over the wavelength range 290-385 nm
  has been used to measure UV radiation. The UV
  radiometer has been operating fairly continuously
  since 1977. The radiometer is logged 50 times per
  minute and the mean values for 10 min, 1 h and 24
  h time intervals are stored.
• The data has been used to study UV effects on
  plant growth and the mechanical properties of
  materials as well as to assess atmospheric models
  of radiative transfer.

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Solar irradiance measurements
Eppley radiometer (UV, 295-385 nm)
Global irradiance
irradianceGG14 (495-2800 nm)
irradiance RG2 (630-2800 nm)
irradiance RG8 IR (695-2800 nm)
Global irradiance
Radiation energy balance
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The Eppley radiometer
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Norwegian intercomparison 1995 I

• The first Norwegian UV- and PAR intercomparison
  meeting 2 was held at the University of Oslo in
  the period 5-9 June 1995. Outdoor synchronous
  solar UV measurement as well as measurements of a
  portable lamp unit from the Swedish Radiation
  Protection Authority (SSI) were conducted.
• The Eppley radiometer was examined for stability
  during the measurement period. In addition, the
  lamp and sky measurements were compared to a
  Macam spectroradiometer (Norwegian Radiation
  Protection Authority). The spectroradiometer had
  been calibrated prior to the intercomparison.
• The Eppley radiometer performed satisfactorily.
  Instrument drift did not occur. The Eppley
  radiometer deviated by approximately 10 from the
  Macam spectroradiometer for both lamp and sky
  measurements.

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Norwegian intercomparison 1995 II

• Eppley TUVR measurements of SSIs 100 W and 150 W
  lamps.

• Ratio between the broadband irradiance provided
  by the Eppley TUVR and the Macam spectrometer for
  daylight (7.06.1995) and lamp measurements. Error
  10.

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Further work

• In order to assure the reliability of the data,
  proper calibration routines for the Eppley
  radiometer must be established. These routines
  should include an in the field method. This
  method should be easy to conduct such that the
  radiometer can be frequently examined for
  abnormalities. The radiometer should also be
  calibrated in the laboratory once a year. The
  calibration factor should be modified
  accordingly.
• The Eppley radiometer has been operating fairly
  continuously since 1977. Valuable data has been
  collected during this period. Additional
  instruments i.e. a multiband filter radiometer or
  another single band filer radiometer should be
  purchased to provide overlap between the data.
• Further analysis of the data will be conducted.
  The databases will be also be made available on
  WWW.

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References

• G. Kvifte, K. Hegg, V. Hansen. 1983. Spectral
  distribution of solar radiation in the Nordic
  countries. Journal of climate and applied
  meteorlogy, 22143-152.
• The 1995 intercomparison of UV- and PAR
  instruments at the University of Oslo. Strålevern
  Rapport 19977, Statens Strålevern. Editors Bjørn
  Johnsen and Merete Hannevik. Authors Bjørn
  Johnsen, Cecilia Futsæther, Arne Dahlback, Arne
  Auen Grimnes, Merete Hannevik, Trond Morten
  Thorseth, Berit Kjeldstad, Tor de Lange, Arvid
  Skartveit, Lars Opedal, Oddbjørn Mikkelborg, Gry
  Storsveen. ISSN 0804-4910.