UNDERWATER RADIATION MEASUREMENTS: CONSEQUENCES OF AN INCREASED UV-B RADIATION - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 186

2. Methods
UV can be measured underwater in the same way as done in air. The most
commonly used instrumentation is broadband meters, which are robust, without any
moveable parts and easy to deploy into the water. Spectroradiometers too have been
deployed, also used in combination with fibres and an optical head. Both downwards
and upwards radiation can be measured and the instruments are deployed at different
depth in order to measure attenuation as a function of depth. For measuring profiles a
surface unit is strongly recommended to correct for rapid changes in radiation reaching
the surface as the profile is carried out.
The instrumentation used in this work was a Biospherical PUV500/510
radiometer with 4 channels in UV (305 nm, 320 nm, 340 nm and 380 nm) and one
channel measuring Photosynthetic Active Radiation (PAR) in addition to temperature
and depth sensors (Figure 1)
Figure 1. Underwater radiometer measuring downward radiation at 4 UV bands (305 nm, 320 nm,
340 nm and 380 nm) and PAR (Biospherical PUV500) underwater unit (black right) and air unit
(Biospherical PUV 510) (white left).
Calibration of underwater radiometers are done in the same way as for
instrument measuring in air 5 . Examples of profiles for 4 UV channels are shown in
Figure 2 . The difference in UV irradiance at the ground for different wavelength can be
observed from the surface values. The absolute irradiance level depended on solar