Recent strong decadal change of Meiyu in 121 years

A strong decadal change of the Meiyu periods in the mid-lower Yangtze basin occurred in late 1970s since 1885:a weak Meiyu stage in 1959-1978 abruptly transformed into the strong one during 1979-1999.The average Meiyu amounts of later 21 years increased by 66% compared with the former years,accompanied with a significant increase of the occurrence of the summer waterlogging in the mid-lower Yangtze basin.The change of Meiyu periods is closely related with the frequently postponed phenomena of their ending dates and the later onsets of high summers in the mid-lower Yangtze.In a considerable degree,it reflects an abrupt change of the summer climate in eastern China.Through analysis,it is found that the preceding factors effecting the inter-annual changes of Meiyu in above 2 stages are also very different from each other.The causes of such decadal change are associated with following strengthening anthropogenic activities:China's industrialization has greatly accelerated since 1970s,accompanied with the increase of the atmospheric pollution and the reduction of the solar radiation on the ground,the sand area of northern China also expands fastly by overgrazing,and the enhanced greenhouse effect is significantly manifested in winter warming(especially in February).Meanwhile,the January precipitation of the mid-lower Yangtze tends to increase,and the El-nino events have occurred more frequently since late 1970s.The correlation-scattered diagram formed by above 5 factors clearly shows that the 2 stages with opposite anomalies of Meiyu period are grouped with the 2 totally locations and very different environmental(land-atmosphere) conditions.Now we have very possibly faced again a new stage of lesser Meiyu starting in 2000.