This dataset contains direct measurement of solar actinic UV flux from which photolysis frequencies are calculated made at the Institute of Atmospheric Physics land station (IAP), Beijing site during the summer and winter APHH-Beijing campaigns for the Atmospheric Pollution & Human Health in a Chinese Megacity (APHH) programme. Photolysis rates were derived from the product of absorption cross-section of the precursor molecule, the quantum yield of the photo-product and the actinic flux density (cm-2s-1nm-1). The actinic flux is measured between 280 - 650 nm (<1 nm resolution) using a spectral radiometer attached to a quartz receiver optic. Absorption cross sections and quantum yields are taken from the latest IUPAC recommendations. The instrument was calibrated between 250 - 750 nm using a spectral Irradiance of Standard Tungsten-Halogen lamp before and after the campaign.

Biologically relevant radiation has been recorded since February 1997 using a Bentham spectroradiometer at Rothera. The Bentham spectroradiometer is sited on the roof of the Bonner Laboratory at Rothera. It measures spectral global irradiance between 280 and 600 nm (wavelengths from below UV-B to the middle of the visible range) with a step size of 0.5 nm and a resolution of 1 nm. Scans are recorded at various time intervals depending on the time of day and season peaking at every 30 minutes while the sun is above the horizon from the beginning of September until the end of April. These scans can be used to measure the amount of solar radiation reaching the earth''s surface at Rothera. It provides particularly useful background data for studies on the effects of increased UV-B, due to the ozone hole, on the plants and microbes in regions around Rothera.