Precipitatation Series Over The Past 1000 Years Are Preliminarily Reconstructed And Analysed In The North-west Of China

The North-west of China is sensitive area of climate change. Climate change research in this area can help to understand climate change regular and provide evidence for climate forecast. In this study, based on consistency characteristic of precipitation variation in different area from the north-west of China, the annual precipitation were reconstructed in the North of Xinjiang province and in the middle part of the North-west China using tree-ring, which series length are from 1543 to 2001 and from 1005 to 2001, respectively.The reconstructed series are analyzed with statistical methods. The pluvial periods of low-frequency are found that the North of Xinjiang province is the same with middle part of the North-west China in AD 1557-1591, 1620-1641, 1732-1746, 1868-1906, 1935-1962 and 1981-2001, and the drought periods in 1697-1731, 1808-1844,and 1916-1932.The periodic cycles from forty years to seventy years are significant in the North of Xinjiang province, and quasi-200-year cycle is present during the whole time period (AD 1543-2001), while quasi-200-year cycle is significant and quasi-120-year and 50-year cycle is present in different time in middle part of the North-west China. In particular, the periodic statistical characteristics are different among each time periods.The study show periodic variation of quasi-200-year cycle, quasi-120-year cycle and the periodic cycles from forty years to seventy years is common in North-west of China.The abrupt changes are also detected in the annual precipitation series, by the scanning t test, the scanning F test and the scanning Lepage test methods. The abrupt changes of the average value are at the same time present in AD 1820s-1830s and in the first two years of 20 century in two regions. In North of Xinjiang province abrupt changes are found frequently and the scale time is large in comparison with in middle part of the North-west China.Through comparing with different researcher, we found that abrupt changes happen consistently in the first semicentury of 18 century, in the last of 19 century and 20 century in different area.