Centennial changes of drought/flood spatial pattern in eastern China for the last 2000 years

The statistical characteristics of the bicentennial changes of the drought/flood spatial pattern over the eastern part of China have been analyzed from 101 AD to 1900 AD, and their relationship with the cold/warm climatic variation in the same time span are discussed as well. The main conclusions are as follows. (I) During the period of the 2nd ～ 11th centuries, the spatial pattern of drought/flood in the eastern part of China was characterized by thc east-west differentiation. Namely, it was dry in the west (northwest) while it was wet in the east (southeast). (ii) From the 12th to 15th centuries, the east-west differentiation coexisted with the south-north differentiation, and the former was still the dominant pattern. (iii) However, the dominant spatial pattern changed to the south- north differentiation during the 16th ～ 19th centuries, namely, it was dry in the north and wet in the south. As for the dry-wet demarcation line. It shifted westward in warn times, and once reached Datong-Taiyuan-Xi' an-Hanzhong; whereas in cold times, it retreated southeastward and reached Ji' nan-Heze-Nanyang. Furthermore, the transmeridian (W-E) dry-wet demarcation line was replaced by the meridian (N-S) dry-wet demarcation line during the two coldest periods. Moreover, in cold times, it was dry in northern China, and it was wet in the middle and lower reaches of Changjiang River and regions south of Changjiang River; in warm times, however, it was wet in northern China, and was dry in eastern China, especially in the lower reaches of Changjiang River and regions south of Changjiang River.