Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-...Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-line of the middle Qilian Mountains within the upper reaches of Heihe River Basin, Northwest China for a long-term reconstruction of temperature at the study site. In this paper, tree-ring chronology was used to examine climate-growth associations considering local climate data obtained from Qilian Meteorological Station. The results showed that temperatures correlated extremely well with standardized growth indices of trees (r=0.564, P<0.001). Tree-ring chronology was highest correlated with annual mean temperature (r=0.641, P<0.0001). Annual mean temperature which spans the period of 1445–2011 was reconstructed and explained 57.8% of the inter-annual to decadal temperature variance at the regional scale for the period 1961–2011. Spatial correlation patterns revealed that reconstructed temperature data and gridded temperature data had a significant correlation on a regional scale, indicating that the reconstruction represents climatic variations for an extended area surrounding the sampling sites. Analysis of the temperature reconstruction indicated that major cold periods occurred during the periods of 1450s–1480s, 1590s–1770s, 1810s–1890s, 1920s–1940s, and 1960s–1970s. Warm intervals occurred during 1490s–1580s, 1780s–1800s, 1900s–1910s, 1950s, and 1980s to present. The coldest 100-year and decadal periods occurred from 1490s–1580s and 1780s–1800s, respectively, while the warmest 100 years within the studied time period was the 20<sup>th</sup> century. Colder events and intervals coincided with wet or moist conditions in and near the study region. The reconstructed temperature agreed well with other temperature series reconstructed across the surrounding areas, demonstrating that this reconstructed temperature could be used to evaluate regional climate change. Compared to the tree-ring reconstructed temperature from nearby regions and records of glacier fluctuations from the surrounding high mountains, this reconstruction was reliable, and could aid in the evaluation of regional climate variability. Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Ni?o–Southern Oscillation (ENSO).展开更多
针对我国高寒山区河流的最佳集水面积阈值确定的问题,选取黑河上游山区为研究区,利用SWAT(soil and w ater assessment tool)模型的流域离散模块(w atershed delineator)基于DEM提取河网,探讨河网总长度与集水面积阈值关系曲线法和适度...针对我国高寒山区河流的最佳集水面积阈值确定的问题,选取黑河上游山区为研究区,利用SWAT(soil and w ater assessment tool)模型的流域离散模块(w atershed delineator)基于DEM提取河网,探讨河网总长度与集水面积阈值关系曲线法和适度指数法在高寒山区的适用性.结果表明:两种方法所对应的最佳集水面积阈值相差较大,所提取的河网难以反映河流真实情况,效果较差,主要原因是上述方法仅考虑流域面积、地形和几何特征的影响,缺乏对降水和其他下垫面因子的综合考虑.相较而言,利用蓝线河网推求最佳集水面积的适度指数法的效果较好.在高寒山区进行河网提取时,应综合考虑影响河网发育的各个因素,在流域分区的基础上,通过不同集水面积阈值实验,获取更高精度的数字河网,改善分布式水文模型的空间离散效果.展开更多
基金supported by the National Natural Science Foundation of China(91025002,30970492)the National Key Technology Research&Development Program(2012BAC08B05)the Key Project of the Chinese Academy of Sciences(KZZD-EW-04-05)
文摘Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-line of the middle Qilian Mountains within the upper reaches of Heihe River Basin, Northwest China for a long-term reconstruction of temperature at the study site. In this paper, tree-ring chronology was used to examine climate-growth associations considering local climate data obtained from Qilian Meteorological Station. The results showed that temperatures correlated extremely well with standardized growth indices of trees (r=0.564, P<0.001). Tree-ring chronology was highest correlated with annual mean temperature (r=0.641, P<0.0001). Annual mean temperature which spans the period of 1445–2011 was reconstructed and explained 57.8% of the inter-annual to decadal temperature variance at the regional scale for the period 1961–2011. Spatial correlation patterns revealed that reconstructed temperature data and gridded temperature data had a significant correlation on a regional scale, indicating that the reconstruction represents climatic variations for an extended area surrounding the sampling sites. Analysis of the temperature reconstruction indicated that major cold periods occurred during the periods of 1450s–1480s, 1590s–1770s, 1810s–1890s, 1920s–1940s, and 1960s–1970s. Warm intervals occurred during 1490s–1580s, 1780s–1800s, 1900s–1910s, 1950s, and 1980s to present. The coldest 100-year and decadal periods occurred from 1490s–1580s and 1780s–1800s, respectively, while the warmest 100 years within the studied time period was the 20<sup>th</sup> century. Colder events and intervals coincided with wet or moist conditions in and near the study region. The reconstructed temperature agreed well with other temperature series reconstructed across the surrounding areas, demonstrating that this reconstructed temperature could be used to evaluate regional climate change. Compared to the tree-ring reconstructed temperature from nearby regions and records of glacier fluctuations from the surrounding high mountains, this reconstruction was reliable, and could aid in the evaluation of regional climate variability. Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Ni?o–Southern Oscillation (ENSO).
文摘针对我国高寒山区河流的最佳集水面积阈值确定的问题,选取黑河上游山区为研究区,利用SWAT(soil and w ater assessment tool)模型的流域离散模块(w atershed delineator)基于DEM提取河网,探讨河网总长度与集水面积阈值关系曲线法和适度指数法在高寒山区的适用性.结果表明:两种方法所对应的最佳集水面积阈值相差较大,所提取的河网难以反映河流真实情况,效果较差,主要原因是上述方法仅考虑流域面积、地形和几何特征的影响,缺乏对降水和其他下垫面因子的综合考虑.相较而言,利用蓝线河网推求最佳集水面积的适度指数法的效果较好.在高寒山区进行河网提取时,应综合考虑影响河网发育的各个因素,在流域分区的基础上,通过不同集水面积阈值实验,获取更高精度的数字河网,改善分布式水文模型的空间离散效果.
