This summer's devastating floods are the result of abnormal weather conditions in the country's south generated by excessive moisture on the Qinghai-Tibet Plateau and a massive rain belt in the western Pacific Ocean, according to a leading mainland climatologist. Li Weijing , a vice-director of the National Climate Centre at the China Meteorological Administration, said several factors had increased moisture in the south in the lead-up to the floods. 'More than usual amounts of snow and ice accumulated on the Qinghai-Tibet Plateau during the winter and spring of this year,' Dr Li said. As it warmed in summer, the snow melted and raised water levels in rivers. The plateau, with an average elevation of 4,000 metres, is the source of China's major rivers. Dr Li said a powerful rain belt produced by western Pacific Ocean subtropical anticyclones - high pressure systems - and summer monsoons prevailing in the South China Sea from the end of last month had sped up convection and ensured there was ample water vapour in the south. The volume of rain this month in regions south of the Yangtze River is as much as double the average for this time of year. The situation is particularly acute in Guangxi and the central and eastern parts of Guangdong.