Abstract: Based on the historical record, dry/wet series since 1470-2008 AD in Northwest China were reconstructed and analyzed. The dry/wet series for 7 regions are expressed by five grades, and dry/wet climate is obtained from a cluster analysis on annual data during 1470-2008 at 19 stations in Northwest China. The variation feature of the dry/wet series, such as phase characteristics, periodicity and abrupt change, are presented. The results show that the reconstruction of sequence reliability is high, and it can be used as a dry/wet climate change research. Wavelet analysis shows that those periodicities existed in the last 500 years, such as the periods of around 11 year, 25-35 year, 80-100 year. Among them, 11 years and 35 years periodicities in the whole analysis period are relatively stable than 80-100 years periodicities. The signs of abrupt changes in the 7 regional dry/wet series were detected by moving t-test. It is indicated that abrupt climatic changes have occurred for every regions in Northwest China during 1470-2008 AD. Both edge of the study area, such as Shaanxi and Yushu, abrupt signal appears fewest times; Ningxia and Golmud is second; the signal appears most times in the middle study area such as Lanzhou, Zhang ye, Xining. It means middle area is the sensitive area of dry/wet climate change. The dry/wet abrupt signal mainly concentrated in the 17th century, dry/wet climate change in recent century is relatively stable.

Key words: dry/wet climate, climate reconstruction, periodicities, abrupt change, Northwest China