Reconstruction of May—July precipitation in the north Helan Mountain, Inner Mongolia since A.D. 1726 from tree-ring late-wood widths

Inrecentyears,greatprogressofdendroclimatologystudyhasbeenmadeinChina,andlotsofvaluabledatahavebeenobtained.Theclimaticfactors,suchastem-perature,precipitation,etc.,havebeenreconstructedonthebasisoftree-ringdataforthepastseveralcenturies[1—5].Thesedatahaveplayed(orwillplay)animportantroleinbothregionalandglobalchangeresearches[6].Sofar,however,tree-ringdatafromtheboundaryofthedeserttoloessareainnorthwestChinaaresparse[7].Thisstudywillusethetree-ringdataintermsofthestatisticalmethodtoreconstr…     

利用树木年轮重建马鞍山地区7～9月降水量序列

利用采自马鞍山地区兴安落叶松(Dahurian Larch)树轮样芯,建立了树轮标准化年表.根据建立的年表,对马鞍山地区树木生长与月降水量进行了响应分析,重建了该地区1942年以来7~9月降水量序列.检验表明,重建方程稳定,重建序列可信.重建结果显示:马鞍山地区7~9月降水量有较小的逐年减小趋势;1942~1957年马鞍山地区降水量处在枯水期;1957~1989年马鞍山地区降水量处在丰水期;1989年往后马鞍山地区降水量又出现一个枯水期的变化过程.     

A 457-year reconstruction of precipitation in the southeastern Qinghai-Tibet Plateau, China using tree-ring records

This paper presents a 457-year reconstruction of precipitation in the southeastern Qinghai-Tibet Plateau using tree-ring records.Tree-ring samples were collected from the Hengduan Mountains in the southeastern part of the Qinghai-Tibet Plateau,China.A nearly 500-year chronology was developed using tree-ring width records.Correlation analysis shows moisture is the main factor limiting tree growth in this region.Ring-widths were significantly positively correlated with the Palmer Drought Severity Index(PDSI) and precipitation in many months.The highest correlation coefficient was found between the annual growth of trees and precipitation from the previous September to the current June(0.738).Based on this relationship,we reconstructed the precipitation history from 1509 to 2006.The reconstruction explains 54.4%(Radj2=53.5%,N=49,F=56.12) of the actual precipitation variation during the calibration period(1958-2006).During the reliable period of the reconstruction(1549-2006),some low-frequency climate signals are included,indicating this region has been getting wetter in the last 20 years.The reconstruction documents six apparently dry and five pluvial periods and the 17th century dry period lasted longer than any other.When compared with other recent studies,this study and these earlier reconstructions show a similar trend in the variation of drought and pluvial.Further spatial correlation analysis confirms that the reconstructed precipitation adequately represents the rainfall history of the entire Hengduan Mountain area.The Multi-taper method,a type of spectral analysis,reveals that precipitation in this area had significant(P<0.01) spectral peaks at 3-5 a,60 a and 79-85 a.     

A tree-ring-based reconstruction of the Yimin River annual runoff in the Hulun Buir region, Inner Mongolia, for the past 135 years

Based on the relationships between the regional tree-ring chronology(RC) of moisture-sensitive Pinus sylvestris var.mongolica and the monthly mean maximum temperature,annual precipitation and annual runoff,a reconstruction of the runoff of the Yimin River was performed for the period 1868-2002.The model was stable and could explain 52.2% of the variance for the calibration period of 1956-2002.During the past 135 years,21 extremely dry years and 19 extremely wet years occurred.These years represented 15.6% and 14.1% of the total study period,respectively.Six severe drought events lasting two years or more occurred in 1950-1951,1986-1987,1905-1909,1926-1928,1968-1969 and 1919-1920.Four wetter events occurred during 1954-1959,1932-1934,1939-1940 and 1990-1991.Comparisons with other tree-ring-based streamflow reconstructions or chronologies for surrounding areas supplied a high degree of confidence in our reconstruction.Power spectrum and wavelet analyses suggested that the reconstructed annual runoff variation in the Hulun Buir region and surrounding area could be associated with large-scale atmospheric-oceanic variability,such as the Pacific Decadal Oscillation(PDO) and El Ni o-Southern Oscillation(ENSO),and sunspot activity.     

章士钊"农本"思想蠡测

民初政治的乌烟瘴气、社会改造的艰难历程、西方文化和现实社会弊病的日渐暴露,使得章士钊对现实产生了怀疑,对传统萌生了眷念.而一战的深刻触动和1921-1922年欧洲之旅的直接影响,使其内心时刻涌动的传统思想终获"重生","农本"主张随之出炉.     

Millennial temperature reconstruction based on tree-ring widths of Qilian juniper from Wulan, Qinghai Province, China

The climate of the past 1000 years is an important context for evaluating the recent climate warming. However, there are few 1000-year-long climate reconstructions with annual resolution in the Qinghal-Tibet Plateau. In this paper, a dendroclimatic analysis was conducted for the radial growth of Qilian juniper from the upper forest limit in Wulan, Qinghai Province. The results of correlation analysis between the tree-ring widths and the climate variables indicate that the growth of junipers at the upper forest limit is mainly limited by low temperatures of September, November and February of the pregrowth season, and July of the current growth season. There is no significant correlation between the tree-ring widths and precipitation. A mean temperature from the previous year＇s September to the current year＇s April was reconstructed for the Wulan area since A.D. 1000. The reconstruction can explain 40.8% of the instrumental variance in the calibration period （1856-2002）. The reconstruction shows that the 20th century is the warmest 100 years, and the 1990s is the warmest decade during the past 1000 years, while the coldest 100 years and decade occur at 1600-1699 and 1642-1651, respectively. The variations are verified well by the temperature reconstruction of the middle Qilian Mountain （QL） and the total organic carbon （TOC） in the Qinghai Lake sediments. The comparison of our reconstruction with the annual temperature reconstruction of extra-tropical Northern Hemisphere suggests that the climate of Wulan during the Medieval Warm Period is of obvious regional specialty, but there was a good response to the climate of hemispheric scales during the recent 400 years.     

近一个半世纪来得法降水的变化特征

利用香港1853－1996年月降水资料,对香港19个时距,包括1－12月,春、夏、秋、冬、前、后汛期和年降水做了特征分析,发现香港降水有其显著的气候特征。     

我国东北地区主要城市气温和降水量序列的多尺度分析

根据1961~2010年东北地区35个主要城市站的逐日气温及降水资料,采用线性拟合、小波变换、经验正交函数分解、Mann-Kendall突变检验和R/S分析等方法,分析了我国东北地区主要城市的气温和降水的变化。结果表明:近50年东北主要城市年平均气温呈上升趋势,其中20世纪80年代后期至90年代初增温幅度最大;城市气温变化存在明显的16a尺度年代际变化周期和(7~8)a、4 a和准2 a尺度的年际变化周期,其中4a尺度的低频振荡能量最强;城市化进程对气温变化影响显著。东北地区主要城市的年降水量减少趋势明显,其中20世纪60年代中期至80年代初降水减少幅度最大;年总降水变化存在准2 a、4 a和(9~10)a尺度的年际变化周期,其中4 a和(9~10)a振荡能量最强;夏季出现特涝的概率大于特旱,大涝的几率小于大旱;同时7月份是东北局部特大洪涝或干旱的多发时段。     

滇中城市降水特征及其成因分析

基于滇中城市群4个主要城市(昆明、曲靖、玉溪和楚雄)近50年的降水资料, 利用统计分析、小波分析、累计距平和灰色关联度分析等方法, 分析滇中城市降水量的年、季、月变化特征以及影响降水量的各种因子。结果表明, 滇中城市近50年平均降水量为928.1 mm, 整体上呈下降趋势, 并在2009年发生突变; 降水量有干、湿季之分, 雨季(5—10月)降水多, 干季(11月至次年4月)降水少, 最大降水量出现在7月(184.0mm), 最小降水量出现在12月(13.8 mm)。通过小波分析, 发现年降水量呈现22年左右的主周期变化; 夏季降水量呈现以19天为主周期的增减变化, 降水多, 变幅小; 冬季降水量呈现以20天为主周期的增减变化, 降水少, 变幅大。通过灰色关联度分析, 发现自然因子中对降水影响较大的是气温和相对湿度, 人文因子中对降水影响最大的是人口和城市面积, 并且, 自然因子的作用大于人文因子。     

地理地形因子对长江中下游平原降水空间分布影响的估算和分析

本文以长江中下游平原为研究区,采用2001-2010十年的降水整编资料、NCEP风向资料以及DEM数据,利用偏最小二乘法（PLS）对长江中下游平原一月、四月、七月、十月的降水空间分布与地理地形因子及风向因子的关系进行分析、检验和讨论。结果表明：与普通克里格插值法对实测降水量进行降水空间分布估算结果相比,加上地理地形因子及风向因子后的PLS回归模型更能直观反映出该区降水空间分布受到局部地理地形因子及风向因子综合影响的特征,其结果能为该区实行因地制宜的工农业生产提供科学的指导。     

Climate change over southern Qinghai Plateau in the past 500 years recorded in <Emphasis Type="Italic">Sabina tibetica</Emphasis> tree rings

Two tree ring-width chronologies of Sabina tibetica were developed based on cores sampled in Qumalai and Zhiduo, southern Qinghai Plateau. The response function analysis showed that the chronologies were sensitive to temperature and precipitation from April to June in the plateau. Moisture index (MI) was defined, reconstructed and extended back to AD 1550. The cross-validation method was used to check the stability of the calibration equation, and the result indicated that the equation was stable. Six severe dry periods were found in this region in the past 453-year reconstruction, which were 1592 to 1610, 1649 to 1665, 1687 to 1697, 1740 to 1750, 1818 to 1829 and 1918 to 1933. Five severe wetting periods were 1669 to 1682, 1700 to 1709, 1800 to 1814, 1898 to 1909 and 1935 to 1950. Spectrum analysis indicated that there existed long-term cycles of 60.4 and 53.4 a, solar cycle of 11 a and short-term cycles of 8, 6 and 4 a in the reconstructed series.     

Climate change over southern Qinghai Plateau in the past 500 years recorded in Sabina tibetica tree rings

Two tree ring-width chronologies of Sabina tibetica were developed based on cores sampled in Qumalal and Zhiduo, southern Qinghai Plateau. The response function analysis showed that the chronologies were sensitive to temperature and precipitation from April to June in the plateau. Moisture index (MI) was defined, reconstructed and extended back to AD 1550. The cross-validation method was used to check the stability of the calibration equation, and the result indicated that the equation was stable. Six severe dry periods were found in this region in the past 453-year reconstruction, which were 1592 to 1610, 1649 to 1665, 1687 to 1697, 1740 to 1750, 1818 to 1829 and 1918 to 1933. Five severe wetting periods were 1669 to 1682, 1700 to 1709, 1800 to 1814, 1898 to 1909 and 1935 to 1950. Spectrum analysis indicated that there existed long-term cycles of 60.4 and 53.4 a, solar cycle of 11 a and short-term cycles of 8, 6 and 4 a in the reconstructed series.     

Reconstruction of precipitation in the last 140 years from tree ring at south margin of the Tengger Desert, China

Based on the tree ring width index of Pinus tabulaeformis, precipitation in the last 140 years was reconstructed at south margin of the Tengger Desert. The results indicated that there were obvious fluctuations of dry-wet changes in precipitation： two wet periods occurred during 1868-1876 and 1932-1939, and two dry periods during 1877-1894 and 1924-1932, however, the years 1887 and 1888 were a little wet. There were small changes in precipitation during 1895-1923 and 1940-2000. As compared to the average, the maximum increasing range of precipitation amounted to 56% during the wet periods, and 42% during the dry periods. And the range of variability of precipitation exceeded 30% in 19 years. There was no obvious consistent drying or wetting trend in the last 140 years. But since 1940 fluctuating scope of precipitation tended to be smaller, while the frequency of the fluctuation tended to be larger. Power spectrum analyses suggested that precipitation of south margin of the Tengger Desert had significant periodicities of 2.46-2.64 a and quasi periodicity of 11.67 a.     

Decadal change of the East Asian summer monsoon and its related surface temperature in Asia-Pacific during 1880–2004

The East Asian summer monsoon （EASM） and its related change of surface temperature in the past century were not clearly ad- dressed due to absence of atmospheric reanalysis data before 1948. On the benchmark of station-observed sea level pressure （SLP） in China, we utilized multiple SLP datasets and evaluated their qualities in measuring the SLP-based EASM index （EASMI）. It is found that the EASMI based on the SLP of the Hadley center version 2 （HadSLP2） has shown the best performance on the inter- annual and decadal time scales. Instead of showing a linear weakening trend pointed out by the previous study, the EASMI has likely exhibited the decadal variability, characterized by weakened trends during 1880-1906, 1921-1936, and 1960-2004, and with enhanced trends during 1906-1921 and 1936-1960, respectively. Corresponding to the weakened and enhanced periods of EASMI since the 1920s, the surface air temperature （SAT） index （SATI） averaged in eastern China has likely shown a warming and a cooling trend, respectively. However, the decadal abrupt transitions between the two indices do not occur concurrently, which results in a weak correlation between two indices on the decadal time scale. Further analysis indicates that there are four key regions where the SAT is significantly correlated with the EASMI, suggesting the joint impact of surface temperature in Asia-Pacific on the EASM during 1880-2004. In which, the decadal change of SAT near the Lake Baikal plays an important role in the linear trends of the EASM before and after 1960.     

The twentieth century was the wettest period in northern Pakistan over the past millennium

Twentieth-century warming could lead to increases in the moisture-holding capacity of the atmosphere, altering the hydrological cycle and the characteristics of precipitation. Such changes in the global rate and distribution of precipitation may have a greater direct effect on human well-being and ecosystem dynamics than changes in temperature itself. Despite the co-variability of both of these climate variables, attention in long-term climate reconstruction has mainly concentrated on temperature changes. Here we present an annually resolved oxygen isotope record from tree-rings, providing a millennial-scale reconstruction of precipitation variability in the high mountains of northern Pakistan. The climatic signal originates mainly from winter precipitation, and is robust over ecologically different sites. Centennial-scale variations reveal dry conditions at the beginning of the past millennium and through the eighteenth and early nineteenth centuries, with precipitation increasing during the late nineteenth and the twentieth centuries to yield the wettest conditions of the past 1,000 years. Comparison with other long-term precipitation reconstructions indicates a large-scale intensification of the hydrological cycle coincident with the onset of industrialization and global warming, and the unprecedented amplitude argues for a human role.     

High－resolution precipitation variations in the Northeast Tibetan Plateau over the last 800 years documented by sediment cores of Qinghai Lake

Short cores of about 80-cm retrieved from three main basins of th e deepwater areas in Qinghai Lake,the largest inland enclosed lake in China, were studied. Sta-ble isotopes of authigenlc carbonates, grain-size, carbonate and organic matter content at 5-year resolution are used to reconstruct the climatic history over the last 800 years in the Northeastern Tibetan Plateau. Chronology was established according to 210^pb dating and 137^Cs methods and the core corrdation. It is found that cores from different deep basins of the lake can be well correlated. The sedimentary rate is highest in the western basin of the lake and lowest in the east.In the southern basin of the lake where the short core Qing-6is located, the recent average sedimentation rate is 0.1004cm/yr. Variations in effective precipitation recorded by the oxygen isotopes and grain size data durine the last 800 years are consistent with the glacial accumulation record form the Dunde and Guliya ice cores. A dry climate lasted for 300 years from 1200 AD to 1500 AD, followed by a wet period from 1500 to 1560 AD. The two dry periods, 1560 to 1650 AD and 1780 to 1850 AD, were the results of southwest monsoon weakening. The effective precipitation generally increased since 1650 AD due to the strengthening of the Asian South-west Monsoon, resulting in a wet period until the 1950s. Ex-cept the early stage, the Little Ice Age on the Plateau is characterized b y increased effective moisture. Organic mat-ter content, with nearly 200-year cycles, shows similar trend with the atmospheric delta earbon-14 before the 1850s, indi-eating that the bioproductivity responds to solar activity.     

祁连山东部地区高分辨率气候记录研究

利用采自祁连山东部的祁连圆柏树芯样本 ,建立标准化年表 ,并将标准年表的树轮指数与采样点附近的天祝乌鞘岭气象站的温度和降水进行响应函数和相关函数分析 .结果表明 ,树轮标准年表序列与当地 3～ 4月份降水成显著正相关 ,相关系数达 0 .5 2 5 ,不同检验分析方法均说明 ,祁连圆柏树轮宽度年表可以用来重建这一地区近 2 80年来的春季降水变化 .重建的近 2 80年来研究区少雨春季与毗邻的河西走廊干旱区旱灾的历史记录相吻合 ;研究还发现 ,祁连山东部地区春季降水对近 10 0年来全球变暖出现明显的相反响应 ,春季降水有明显的减少趋势 .奇异谱和功率谱分析表明 ,近 30 0年来研究区春季降水主要有准 19a和 15 a两个显著周期     

Meiyu in the middle and lower reaches of the Yangtze River since 1736

＂Yu Xue Fen Cun＂ records during the Qing Dynasty are used to identify the starting and ending dates of Meiyu at the period of 1736-1911. These results, along with the instrumental meteorological records, are used to reconstruct the series of length and precipitation of Meiyu during 1736-2000 over the middle and lower reaches of the Yangtze River. The characteristics of Meiyu are analyzed since 1736. Moreover, the strength of East Asian Summer Monsoon and locations of rainband are discussed, based on the relationship between the length of Meiyu and the Index of East Asian Summer Monsoon. It is found that the starting and ending dates and the length of Meiyu have significant interannual and interdecadal variations. Apart from 7-8 years, 20-30 years and 40 years cycles for the lengths of Meiyu, the centennial oscillation is also presented. The length of Meiyu, monsoon rainband movement over eastern China, and the strength of East Asian Summer Monsoon （EASM） have a very good correlation, which can be expressed in the following： during the periods of 1736-1770, 1821-1870 and 1921-1970, the EASM was stronger, and the monsoon rainband was located in North China and South China easily, corresponding to the decreased length of Meiyu. Whereas during the periods of 1771-1820, 1871-1920 and 1971-2000, the EASM was weaker and monsoon rainband usually stopped at the middle and lower reaches of the Yangtze River, corresponding to the increased length of Meiyu.     

开封市30年降水量和土壤蒸发量特征分析

利用开封市1980-2009年连续30年的降水量资料,分析得出开封市降水量年季变化大、季节分布极不均匀、多雨少雨期交替出现、全年主要降水集中在夏季、夏季平均降水量占全年降水的一半以上的结论,根据开封市1980-2009年各月平均气温和平均湿度,运用伊万诺夫经验公式求出各月及各季的平均土壤蒸发量.开封市月土壤蒸发量与降水...     

十七世纪以来华北中部夏季降水的特征、趋势与影响

本文通过华北中部12务夏季降水曲线的主成分分析,得到代表大区域的夏季降水变化的PPC-1序列．分析显示十七世纪的开始,华北中部是比较湿润的,中叶出现较大的波动,而下半叶降水较为正常;十八世纪整体较为湿润;十九世纪以来,降水呈现下降趋势且年际变化显著增大．谱分析结果显示,夏季降水具有23．8年、8．6年、7．0年和2—5年的显著周期．在假定人类活动强度和其他控制因素不变的情境下,未来4JD年（2011—2050AD）,华北中部地区的夏季降水总体呈现显著下降的趋势．最后,通过分析降水变率与社会进程的时间耦合,认为近四百年来气候变化对中国农耕社会的稳定性具有显著影响．