, Volume 49, Issue 4, pp 408-420
Date: 25 Mar 2006

Precipitation variation in the northeastern Tibetan Plateau recorded by the tree rings since 850 AD and its relevance to the Northern Hemisphere temperature

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Three well-dated Sabina Przewalskii ring-width chronologies from Dulan, China, have been used to reconstruct annual precipitation (from prior July to current June) variations on the northeast Tibetan Plateau since 850 AD. The reconstructions account of the instrumentally recorded precipitation variance are: 54.7% for the period of 1385–2000AD; 50.5% for 1099–1384AD and 45.7% for 850–1098AD. On the millenary scale, the precipitation variation over this region displays “W” shape, which has three peaks and two valleys. The precipitation is low during 1571–1879 AD, and high during 1880–2000 AD. 1900–2000 AD is the century with the highest precipitation over the northeast Tibetan Plateau in the last 1000 years, and 1962–2000 is the period with the highest precipitation, and the highest variability of precipitation as well in the last 1000 years. The reconstructed series also reveals that the variability of annual precipitation is large when the precipitation is more, and contrarily, variability is small when the precipitation is low. With the temperature increasing obviously in the 20th century, the precipitation in the study region significantly increased too, the variability of precipitation became larger, and drought and flooding occurred more frequently.

The yearly tree-ring width (high frequency signal) series in this region reflects the local annually precipitation variation. However, the series with 40-year moving average (low frequency signal) corresponds to the Northern Hemisphere temperature variations on the decadal to centurial scale. It correlates significantly with seven temperature curves of the Northern Hemisphere in the different time spans. For example, the correlation coefficients with the most temperature curves are around 0.9 during the period of 1852–1982 AD. In general, the temperature and the precipitation change synchronously in the Dulan region. It means that low temperature corresponds to low precipitation, and vice versa. This relationship may indicate that the climatic pattern is the combination of warm-wet and cold-dry on centenary to millenary scale over the Northern Tibetan Plateau in the past 1000 years. The departure series of 40-year moving average could be regarded as the millenarian temperature curve with annual resolution over the northeast Tibetan Plateau region.