Influence of the El Niño southern oscillation on the total ozone column and clear-sky ultraviolet radiation over China

The influence of the El Niño Southern Oscillation (ENSO) on the total ozone column (TOC) and clear-sky ultraviolet (UV) radiation over China is analysed using various datasets and a chemistry-climate model. Higher TOC values than normal are found over most parts of China during El Niño events. La Niña events have almost the opposite effect on TOC anomalies over China. It is particularly noticeable that the maximum response of the TOC to ENSO shifts northward from southern China in winter to northern China in summer. The seasonal shift of the centre of TOC anomalies is related to the seasonal shift of the location of the East Asia westerly jet, accompanied by tropopause height changes and anomalous circulations induced by Rossby wave trains along the jet. The differences in the TOC between El Niño and La Niña events can cause up to 6-10% clear-sky erythemal UV changes over the middle and lower reaches of the Yangtze River in winter and the northwestern Tibetan Plateau during spring, which may have public health consequences.