Title: Solar UV measurements at the Agricultural University of Norway Cecilia Futsaether and Arne Auen Grim
1Solar UV measurements at theAgricultural
University of NorwayCecilia Futsaether and Arne
Auen Grimnes, Dept. of Agricultural Engineering,
Agricultural University of Norway, N-1432 Ås,
Norway.
2Measurement 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.
3The meteorological station
4Meteorological measurements
5Solar 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.
6Solar 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
7The Eppley radiometer
8Norwegian 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.
9Norwegian 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.
10Further 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.
11References
- 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.