The variation of moisture conditions in China during the last 2000 years

Utilizing more than 50,000 reports of droughts and floods found in local records we have reconstructed the history of moisture conditions in eastern China for the last 2000 years. The area studied extends eastward of Gansu province and is situated between Inner Mongolia in the north and Zhejiang in the south. Separate analyses are presented for the semi‐arid, semi‐wet and wet subdivisions of this area. It was possible to develop moisture indices with a time resolution of 5 years in each subregion. The time series of the moisture index presented for the semi‐wet area extends over the period AD 1–1950, while for the other two subregions the period covered is AD 251–1950. Each of the climatic subdivisions is found to undergo prolonged periods of dryness and wetness. The frequency of alternation between dry and wet conditions increases from the semi‐arid region to the semi‐wet region to the wet region. The variations of moisture conditions in the whole area of eastern China is compared with known changes in the level of the Caspian Sea. The variations in the two regions are found to be coherent.