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.