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,and 1978-1989) 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 (1710s,1830s-1840s and 1890s-1900s) and drought periods (1660s,1680s-1690s,1730s-1740s,1820s and 1950s) 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.
[1] MANN Michael E,BRADLEY Raymond S,HUGHES Malcolm K.Global-scale temperature patterns and climate forcing over the past six centuries[J].Nature,1998,392(6678):779-787.
[2] 陈贝,吴涧.青藏高原热力异常对四川省及周边区域气象要素影响分析[J]. 高原山地气象研究,2010,30(3):1-11.[CHEN Bei,WU Jian.Analysis on the influence of Tibetan Plateau thermal anomalies to meteorological elements in Sichuan and neighboring areas[J].Plateau and Mountain Meteorology Research,2010,30(3):1-11.]
[3] ZHAO P,YANG S,YU R C.Long-term changes in rainfall over Eastern China and large-scale atmospheric circulation associated with recent global warming[J].Journal of Climate,2010,23(6):1544-1562.
[4] 王荣英,周顺武,闫巨盛,等.近30年青藏高原上空大气温度变化特征[J].高原山地气象研究,2011,31(1):1-5.[WANG Rongying,ZHOU Shunwu,YAN Jvsheng,et al.Analysis of temporal and spatial characteristics about upper-air temperature over Tibetan Plateau during last 30 years[J].Plateau and Mountain Meteorology Research,2011,31(1):1-5.]
[5] 郑飒飒,李跃清,齐冬梅,等.青藏高原夏季风对长江中下游气候的影响及与南亚高压的联系[J].高原山地气象研究,2014,34(2):30-38.[ZHENG Sasa,LI Yueqing,QI Dongmei,et al.The impact of Tibetan Plateau summer monsoon on the climate of the Yangtze River Basin and contact with South Asia[J].Plateau and Mountain Meteorology Research,2014,34(2):30-38.]
[6] 胡超,张鹏飞.两种厄尔尼诺类型期高原地区大气环流的对比分析[J].高原山地气象研究,2015,35(4):50-55.[HU Chao,ZHANG Pengfei.Analysis of contrast between two atmospheric circulations at plateau section during the period of El-Nino[J].Plateau and Mountain Meteorology Research,2015,35(4):50-55.]
[7] 汤懋苍,李存强,张建.青藏高原及其四周的近代气候变化[J].高原气象,1988,7(1):39-49.[TANG Maocang,LI Cunqiang,ZHANG Jian.The climate change of Qinghai-Xizang Plateau and its neighbourhood[J].Plateau Meteorology,1988,7(1):39-49.]
[8] LIU X D,CHEN B D.Climatic warming in the Tibetan Plateau during recent decades[J].International Journal of Climatology,2000,20(14):1729-1742.
[9] THOMPSON L G,YAO T D,DAVIS Mary E,et al.Tropical climate instability:The last glacial cycle from a Qinghai Tibetan ice core[J].Science,1997,276(5320):1821-1825.
[10] BRIFFA K R,OSBORN T J,SCHWEINGRUBER F H,et al.Low-frequency temperature variations from a northern tree ring density network[J].Journal of Geophysical Research,2001,106(D3):2929-2941.
[11] MANN M E,BRADLEY R S,HUGHES M K.North Hemisphere temperatures during the past millennium:Inferences,uncertainties,and limitations[J].Geophysical Research Letters,1999,26(6):759-763.
[12] 秦宁生,时兴合,邵雪梅,等.川西高原树木年轮所指示的平均最高气温变化[J].高原山地气象研究,2008,28(4):18-24.[QIN Ningsheng,SHI Xinghe,SHAO Xuemei,et al.Average maximum temperature change recorded by tree rings in West Sichuan Plateau[J].Plateau and Mountain Meteorology Research,2008,28(4):18-24.]
[13] 秦宁生,邵雪梅,时兴合,等.青南高原树轮年表的建立及与气候要素的关系[J].高原气象,2003,22(5):445-450.[QIN Ningsheng,SHAO Xuemei,SHI Xinghe,et al. Tree-ring chronology in southern Qinghai and its relation to climatic element[J].Plateau Meteorology,2003,22(5):445-450.]
[14] 秦宁生,邵雪梅,靳立亚,等.青海南部高原圆柏年轮指示的近500年来气候变化[J].科学通报,2003,48(19):2068-2072.[QIN NingSheng,SHAO Xuemei,JIN Liya,et al.Climate change over southern Qinghai Plateau in the past 500 years recorded in Sabina tibetica tree rings[J].Chinese Science Bulletin,2003,48(19):2068-2072.]
[15] 时兴合,秦宁生,邵雪梅,等.青海杂多圆柏年轮指示的近700年旱涝变化[J].高原气象,2009,28(4):769-776.[SHI Xinghe,QIN Ningsheng,SHAO Xuemei,et al.The drought and flood signals in recent 700 years indicated by long tree-rings of Sabina tibetica in Zaduo of Qinghai Province[J].Plateau Meteorology,2009,28(4):769-776.]
[16] 秦宁生,靳立亚,时兴合,等.利用树轮资料重建通天河流域518年径流量[J].地理学报,2004,59(4):550-556,[QIN Ningsheng,JIN Liya,SHI Xinghe,et al.A 518-year runoff reconstruction of Tongtian River Basin using tree-ring width chronologies[J].Acta Geographica Sinica,2004,59(4):550-556.]
[17] LIANG E Y,SHAO X M,QIN N S.Tree-ring based summer temperature reconstruction for the source region of the Yangtze River on the Tibetan Plateau[J].Global and Planetary Change,2008,61(3-4):313-320.
[18] 叶秣麟,秦宁生,白爱娟,等.利用树轮宽度重建黄河源区1618-2009年5~6月最高气温[J].气候变化研究进展,2015,11(2):86-92.[YE Molin,QIN Ningsheng,BAI Aijuan,et al.Using tree-ring width to reconstruct the maximum air temperature of Yellow River source region in May-June over 1618-2009[J].Progressus Inquisitiones de Mutatione Climatis,2015,11(2):86-92.]
[19] HOLMES R L.Computer-assisted quality control in tree-ring dating and measurement[J].Tree-Ring Bulletin,1983,44(3):69-75.
[20] COOK E R.A time series analysis approach to tree-ring standardization[D].Tucson:The Ph.D Dissertation of University of Arizona,1985.
[21] FANG K Y,GOU X H,PETERS K,et al.Removing biological trends from tree-ring series:Testing modified hugershoff curves[J].Tree-Ring Research,2010,66(1):51-59.
[22] 王梦麦,戴君虎,白洁,等.利用树木年轮重建六盘山地区1900年以来的干湿变化[J].古地理学报,2009,11(3):355-360.[WANG Mengmai,DAI Junhu,BAI Jie,et al.Reconstruction of humidity changes from tree rings in Liupan Mountains area since 1900[J].Journal of Palaeogeography,2009,11(3):355-360.]
[23] 魏凤英.现代气候统计诊断与预测技术[M].北京:气象出版社,1999:1-275.[WEI Fengying.Modern weather forecasting techniques and statistical diagnosis[M].Beijing:China Meteorological Press,1999:1-275.]
[24] KOHLER M A.On the use of double-mass analysis for testing the consistency of meteorological records and for making required adjustment[J].Bulletin of the American Meteorological Society,1949,30(1):188-189.
[25] GUEHL J M,AUSSENAC G.Photosynthesis decrease and stomatal control of gas exchange in Abies alba Mill. in response to vapor pressure difference[J]. Plant Physiology,1987,83(2):316-322.
[26] LANG E Y,ECKSTEIN D,LIU H Y.Climate-growth relationships of relict Pinus tabulaeformis at the northern limit of its natural distribution in northern China[J].Journal of Vegetation Science,2008,19(3):393-406.
[27] MANN M E,LEES J M.Robust estimation of background noise and signal detection in climatic time series[J].Climatic Change,1996,33(3):409-445.
[28] 邢佩.青藏高原树轮气候重建与中国东部树种的树轮气候学评价——以青海三江源、西藏昌都和浙江古田山地区为例[D].北京:中国科学院大学博士论文,2013.[XING Pei.Climate reconstruction on the Qinghai-Tibetan Plateau based on tree ring and dendroclimatological evaluation of tree species in eastern China:A case study in Sanjiangyuan region of Qinghai,Changdu prefecture of Tibet and Gutian mountain of Zhejiang[D].Beijing:The Ph.D Dissertation of University of Chinese Academy of Sciences,2013.]
[29] GOU X H,CHEN F H,JACOBY G,et al.Rapid tree growth with respect to the last 400 years in response to climate warming,northeastern Tibetan Plateau[J].International Journal of Climatology,2007,27(11):1497-1503.
[30] ZHANG Q B,CHENG G D,YAO T D,et al.A 2,326-year tree-ring record of climate variability on the northeastern Qinghai-Tibetan Plateau[J].Geophysical Research Letters,2003,30(14):1739.
[31] HUANG J G,ZHANG Q B.Tree rings and climate for the last 680 years in Wulan area of northeastern Qinghai-Tibetan Plateau[J].Climatic Change,2007,80:369-377.
[32] LIANG E Y,SHAO X M,XU Y.Tree-ring evidence of recent abnormal warming on the southeast Tibetan Plateau[J].Theor Appl Climatol,2009,98:9-18.
[33] COOK E R,ANCHUKAITIS K J,BUCKLEY B M,et al.Asian monsoon failure and megadrought during the last millennium[J].Science,2010,328(5977):486-489.
[34] 吕军,屠其璞,钱君龙,等.利用树木年轮稳定同位素重建天目山地区相对湿度序列[J].气象科学,2002,22(1):47-51.[LV Jun,TU Qipu,QIAN Junlong,et al.Relative humidity series reconstructed by using stable isotopes in tree ring of Tianmu Mountain[J].Scientia Meteorologica Sinica,2002,22(1):47-51.]
[35] 温克刚,王莘.中国气象灾害大典-青海卷[M].北京:气象出版社,2006:1-200.[WEN Kegang,WANG Xin.Chinese meteorological disasters encyclopedia:Qinghai volume[M].Beijing:China Meteorological Press,2006:1-200.]
