A CEOF Analysis on Distribution and Interannual Variation of Drought and Flood in China During the Last 100 Years

By using the complex empirical orthogonal function (CEOF) analysis, the spatial and temporal distribution and interannual variation of drought and flood in the east of China in 1850~1991 are investigated. It is found that there are mainly three distribution types of drought and flood in summer of China. In the first type, drought or flood appears in most areas of China around the Changjiang valley, their spatial phases are approximately the same, and there are 10.7 and 3.1 year periodic changes, respectively. There occurred abrupt increase in the time-amplitude during 1923~1924. The second one is the distribution which of drought and flood in the north of China is opposite to that in the south of China, the change of spatial phase from north to south is remarkable, and there are 4.3 year periodic change. There occurred abrupt decrease during 1884~1885. The third one is the distribution which alone the Changjiang and Huaihe valley is opposite to that in North China and Sorth China, the spatial phase moves toward both from north and south to medium or to their reverse direction, respectively, and there are 3.4 year periodic change. The abrupt increase occurred during 1911~1912.