An ensemble weighting approach for dendroclimatology: drought reconstructions for the northeastern Tibetan Plateau.
Traditional detrending methods assign equal mean value to all tree-ring series for chronology developments, despite that the mean annual growth changes in different time periods. We find that the strength of a tree-ring model can be improved by giving more weights to tree-ring series that have a stronger climate signal and less weight to series that have a weaker signal. We thus present an ensemble weighting method to mitigate these potential biases and to more accurately extract the climate signals in dendroclimatology studies. This new method has been used to develop the first annual precipitation reconstruction (previous August to current July) at the Songmingyan Mountain and to recalculate the tree-ring chronology from Shenge site in Dulan area in northeastern Tibetan Plateau (TP), a marginal area of Asian summer monsoon. The ensemble weighting method explains 31.7% of instrumental variance for the reconstructions at Songmingyan Mountain and 57.3% of the instrumental variance in the Dulan area, which are higher than those developed using traditional methods. We focus on the newly introduced reconstruction at Songmingyan Mountain, which showsextremely dry (wet) epochs from 1862-1874, 1914-1933 and 1991-1999 (1882-1905). These dry/wet epochs were also found in the marginal areas of summer monsoon and the Indian subcontinent, indicating the linkages between regional hydroclimate changes and the Indian summer monsoon.
Key Laboratory of Humid Subtropical Eco-Geographical Process (Ministry of Education), College of Geographical Sciences, Fujian Normal University, Fuzhou, Fujian Province, China ; Key Laboratory of Western China's Environmental Systems (Ministry of Education), Research School of Arid Environment and Climate Change, Lanzhou University, Lanzhou, Gansu Province, China ; Department of Geosciences and Geography, University of Helsinki, Helsinki City, Helsinki, Finland.
Keyan
K
Fang
Institute of Botany and Landscape Ecology, Greifswald University, Greifswald, Mecklenburg-Vorpommern, Germany.
Martin
M
Wilmking
Tree-Ring Lab, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, United States of America ; Department of Environmental Science, William Paterson University, Wayne, New Jersey, United States of America.
Nicole
N
Davi
Key Laboratory of Humid Subtropical Eco-Geographical Process (Ministry of Education), College of Geographical Sciences, Fujian Normal University, Fuzhou, Fujian Province, China.
Feifei
F
Zhou
Key Laboratory of Western China's Environmental Systems (Ministry of Education), Research School of Arid Environment and Climate Change, Lanzhou University, Lanzhou, Gansu Province, China.
Changzhi
C
Liu
D000531:Altitude; D002681:China; D002980:Climate; D055864:Droughts; D004463:Ecology / Q000379:methods; D017753:Ecosystem; D005843:Geography; D011891:Rain; D012621:Seasons; D013696:Temperature; D013997:Time Factors; D014197:Trees / Q000254:growth & development*