Tree-ring based reconstruction of relative humidity from May to September in southern Qinghai Plateau during AD 1639—2013
HUANG Xiao-mei;XIAO Ding-mu;QIN Ning-sheng;Chengdu Institute of Plateau Meteorology,CMA/Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province;Sichuan Provincial Meteorological Observatory;Climate Center of Sichuan Province;
The study of relative humidity is important to understand better the past climatic variations. However,there have been few long-term humidity reconstructions using tree-ring widths worldwide. In this paper,we established a reconstruction of mean relative humidity from May to September from AD 1639 to 2013 using Sabina tibetica Kom from the southern Qinghai Plateau region in the northeastern Tibetan Plateau,China. In total,there were 56 tree cores from 28 trees collected at Angsai Township of Zaduo County of Qinghai Province( AS,95°37. 765' E,32°42. 856' N). All samples were surfaced,cross-dated and measured according to standard dendrochronology techniques. The reconstructed equation was stable and reliable and its variance interpretation quantity reached 42. 3%.In the past 375 years,there were five wet periods( 1694—1710,1753—1778,1830—1847,1892—1908,and1978—1989) and eight dry periods( 1646—1673,1682—1693,1711—1731,1735—1752,1796—1809,1817—1829,1848—1861 and 1873—1886) in the reconstructed humidity sequence. The longest wet period is 1753—1778( 26 years),and the longest dry period is 1646—1673( 28 years). There were 12 extremely dry years: 1689,1700,1724,1727,1739,1749,1872,1910,1942,1953,1995 and 1998; and 5 extremely wet years: 1640,1699,1703,1704 and 1873. The multi-taper method( MTM) spectral analysis indicates that there are 3 periodic changes of 28-30 a,6-9 a,2-5 a. The 2-5 a cycle may be related to the Quasi-biennial and Southern Oscillations influenced by the constant change between east wind and west wind in the equatorial stratosphere in a cycle of 26-30 months. The 6-9 a cycle may be related to ENSO. By comparing the reconstructed sequence from this study with a few typical reconstructed series which can reflect the status of dry and wet in the Southern Qinghai Plateau,it is found that there were four curves which shared the same wet periods( 1710 s,1830 s—1840 s and 1890 s—1900 s)and drought periods( 1660 s,1680 s—1690 s,1730 s—1740 s,1820 s and 1950 s) at an inter-annual scale. The result shows that these series presented good consistency on the change of low frequency. Moreover,our relative humidity reconstruction was correlated well with the corresponding grids MADA dataset in the public section during the common period. All of these have proved the accuracy of the reconstruction sequence in this paper.
【Fund】： 国家自然科学基金(41772173);; 中国沙漠气象科学研究基金(Sqj2016002)
【CateGory Index】： P426.1
【CateGory Index】： P426.1