Radiation measurements

The measured wavebands are

• ultraviolet A and B (UVA and UVB, 0.28–0.40 µm)
• photosynthetically active radiation (PAR, 0.4–0.7 µm)
• global shortwave radiation (0.3–4.8 µm)
• thermal infrared radiation (5–40 µm).

A spectroradiometer (Bentham) is measuring the spectrum of incident radiation within wavelengths of 0.28–0.58 µm on the roof of A building.

Basic measurements of the different wavebands of incident radiation (global, UV, PAR) were initially done at the top of the 18-m tall radiation/REA tower and moved to the top of the new 35-m tower in February 2017.

The diffuse component is measured for PAR, reflected radiation for PAR and global radiation.

Direct solar radiation is also measured with automatically tracking sunphotometer for determining atmospheric aerosols and water vapour.

The radiative energy balance of the site is determined with net radiometer (0.3–30 µm), not installed at the moment.

Relationships between reflected and incident radiation at specific wavelengths indicate the optical properties of the vegetation.
The measurements include canopy spectral reflectance, PRI (Photochemical Reflectance Index, 531 and 570 nm) and NDVI (Normalised Difference Vegetation Index, 652 and 860 nm).

Reflected radiation components and spectral measurements are mostly measured in the tall tower (mast).

Spatial and temporal distribution of PAR below the tree canopy is measured at 0.6 m height from the ground in the vicinity of the towers and inside the intensively studied mini-watershed.
The instrumentation consists of

• 4x Li-Cor LI-190SZ quantum sensors (maapar, northeast of REA cottage)
• 15x Apogee SQ-100 quantum sensors in groups of 5 sensors (canpar1 and canpar2 between main cottage and REA cottage, canpar3 east of phototower2)
• ~200 PAR diodes in arrays of 24 or 48 sensors (light pole, retired in 2008)