Spatial and temporal variability of annual and seasonal precipitation over the desert region of China during 1951–2005     

Ligang Xu  Hongfei Zhou  Chuan Liang  Li DU  Hui Li 《水文研究》2010,24(20):2947-2959

The spatial and temporal variations of precipitation in the desert region of China (DRC) from 1951 to 2005 were investigated using a rotated empirical orthogonal function (REOF), the precipitation concentration index (PCI) and the Mann–Kendall trend test method (M‐K method). In addition, the association between variation patterns of precipitation and large‐scale circulation were also explored using the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data. The results indicated that the spatial pattern of precipitation was primarily the local climate effect significant type, with the first three EOFs explaining a total of 55·3% of the variance, and the large‐scale climate system effect type, which explained 9·8% of the variance. Prior to the 1970s, the East Asian summer monsoon was stronger, which resulted in abundant precipitation in the Inner Mongolia region. Conversely, the climate of the Xinjiang region was controlled by westerly circulation and had lower precipitation. However, this situation has been reversed since the 1980s. It is predicted that precipitation will decrease by 15–40 and 0–10 mm/year in the Inner Mongolia plateau and southern Xinjiang, respectively, whereas it will likely increase by 10–40 mm/year in northern Xinjiang. Additionally, 58–62% of the annual rainfall occurred during summer in the DRC, with precipitation increasing during spring and summer and decreasing in winter. The intra‐annual precipitation is becoming uniform, but the inter‐annual variability in precipitation has been increasing in the western portions of the DRC. The probability of precipitation during the study period increased by 30% and 22·2% in the extreme‐arid zones and arid zones, respectively. Conversely, the probability of precipitation during the study period decreased by 18·5% and 37·5% in the semi‐arid zones and semi‐wet zones, respectively. It is predicted that the northwest portion of the DRC will become warmer and wetter, while the central portion will become warmer and drier and the northeast portion will be subjected to drought. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Isotopic composition (δ18O and δD) of precipitation and groundwater in a semi‐arid,mountainous area (Guadiana Menor basin,Southeast Spain)     

F. Fernndez‐Chacn  J. Benavente  J. C. Rubio‐Campos  C. Kohfahl  J. Jimnez  H. Meyer  H. Hubberten  A. Pekdeger 《水文研究》2010,24(10):1343-1356

We characterize the precipitation and groundwater in a mountainous (peaks slightly above 3000 m a.s.l.), semi‐arid river basin in SE Spain in terms of the isotopes ¹⁸O and ²H. This basin, with an extension of about 7000 km², is an ideal site for such a study because fronts from the Atlantic and the Mediterranean converge here. Much of the land is farmed and irrigated both by groundwater and runoff water collected in reservoirs. A total of approximately 100 water samples from precipitation and 300 from groundwater have been analysed. To sample precipitation we set up a network of 39 stations at different altitudes (800–1700 m a.s.l.), with which we were able to collect the rain and snowfall from 29 separate events between July 2005 and April 2007 and take monthly samples during the periods of maximum recharge of the aquifers. To characterize the groundwater we set up a control network of 43 points (23 springs and 20 wells) to sample every 3 months the main aquifers and both the thermal and non‐thermal groundwater. We also sampled two shallow‐water sites (a reservoir and a river). The isotope composition of the precipitation forms a local meteoric water line (LMWL) characterized by the equation δD = 7·72δ¹⁸O + 9·90, with mean values for δ¹⁸O and δD of − 10·28‰ and − 69·33‰, respectively, and 12·9‰ for the d‐excess value. To correlate the isotope composition of the rainfall water with groundwater we calculated the weighted local meteoric water line (WLMWL), characterized by the equation δD = 7·40δ¹⁸O + 7·24, which takes into account the quantity of water precipitated during each event. These values of (dδD/dδ¹⁸O)< 8 and d‐excess (δD–8δ¹⁸O)< 10 in each curve bear witness to the ‘amount effect’, an effect which is more manifest between May and September, when the ground temperature is higher. Other effects noted in the basin were those of altitude and the continental influence. The isotopic compositions of the groundwater are represented by the equation δD = 4·79δ¹⁸O − 18·64. The groundwater is richer in heavy isotopes than the rainfall, with mean values of − 8·48‰ for δ¹⁸O and − 59·27‰ for δD. The isotope enrichment processes detected include a higher rate of evaporation from detrital aquifers than from carbonate ones, the effects of recharging aquifers from irrigation return flow and/or from reservoirs' leakage and enrichment in δ¹⁸O from thermal water. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Long‐term dynamics of fire refuges in boreal mixedwood forests          下载免费PDF全文

SAMIRA OUARMIM  HUGO ASSELIN  CHRISTELLE HÉLY  YVES BERGERON  ADAM A. ALI 《第四纪科学杂志》2014,29(2):123-129

  相似文献   

感潮河段丁坝局部冲刷三维数值模拟   总被引：1，自引：1，他引：0       下载免费PDF全文

张新周  窦希萍  王向明  王惠民  赵晓冬  徐雪松 《水科学进展》2012,23(2):222-228

针对局部冲刷和一般冲刷的不同,建立了考虑垂向水流作用的局部冲刷三维紊流泥沙数学模型,并对往复流和单向流作用下的丁坝局部冲刷进行了验证计算和数值模拟。结果表明,往复流作用下丁坝局部冲刷在冲刷过程和冲淤形态上与单向流有明显不同,若采用单向流作用下的局部冲刷模型试验结果来指导往复流作用下丁坝头防护工程的设计和施工是不利的。  相似文献   

分离重力区域场与局部场的Matlab趋势分析法          下载免费PDF全文

吴琼  秦丽丽 《甘肃地质》2012,(2):88-92

趋势分析法作为场分离的一种方法,当地形情况复杂、测区面积较大时,往往很难达到场分离的要求。文章通过改变多项式数学模型的阶次,选择最优的多项式数学模型进行趋势分析。通过对剖面趋势分析和曲面趋势分析的对比得知,在同一地质模型上剖面趋势分析效果较曲面趋势分析效果好,由此运用切割法将叠加异常数据直接截取,获得多个剖面进行趋势分析,再由剖面趋势分析得到曲面趋势分析。实验结果表明趋势分析效果理想,能达到场分离的要求。  相似文献   

面向类型特征的自适应阈值遥感影像变化检测     

刘红超  张磊 《遥感学报》2020,24(6):728-738

为了实现两个不同年份单时相遥感影像之间的土地覆盖变化检测，提出了一种基于土地覆盖类型特征自适应确定阈值的遥感影像变化检测方法。以2015年土地覆盖数据为基础，综合2013年和2015年Landsat 8-OLI影像数据，首先，采用时相不变点群法TIC（Temporally Invariant Cluster）保证了两期影像辐射水平的一致性。其次，对两期影像进行多尺度分割，并在各级尺度下构建分割对象的变化向量。然后，采用最大类间方差的方法分别进行单一变化阈值变化检测以及基于土地覆盖类型的多阈值变化检测分析，并利用目视解译样点进行精度验证与评价。结果表明：（1）单一阈值变化检测结果的总体精度为79.6%，Kappa系数为0.601，多阈值变化检测结果的总体精度为87.2%，Kappa系数为0.741，多阈值变化检测具有更高的精度。（2）进一步逐土地覆盖类型精度评价可知，多阈值变化检测能在一定程度上减弱物候期的影响，具有更高的稳定性。该研究以土地覆盖数据为底图，逐类别的选取变化检测阈值，提高了变化区域检测的精度，在大范围高效更新土地覆盖数据的应用中具有一定的参考价值。  相似文献   

地方院校一流本科专业建设的探索与实践——以河南城建学院测绘工程专业为例     

高宁  高彩云  丁磊香 《测绘与空间地理信息》2022,(2):13-15,20

地方院校在"一流本科"建设浪潮中,迎来前所未有的发展机遇与挑战.河南城建学院测绘工程专业,基于专业定位与特色优势,积极探索一流本科专业建设策略,以学生为中心,社会需求为导向,从人才培养模式、课程建设、师资队伍、实践教学环境、教育质量保证体系等方面深入改革,提升专业社会综合服务能力,提高人才培养质量,推动一流本科专业建设...  相似文献   

Experimental verification of the turbulent effects on laser beam propagation in space     

《Atmósfera》2014,27(4):385-401

  相似文献   

过山车钢结构精度测量及局部坐标系数据应用     

徐晓玉  刘屈钱 《测绘通报》2022,(12):165-169

常规基于人工的坐标分解计算,在应对逐渐提升的建造要求及特殊产品的应用需求时,存在效率不高、人为误判等情况,本文通过对局部坐标分解应用进行研究及自动坐标分解与重新定向,有效解决了过山车类复杂结构建造尺寸精度管控过程中数据的修正及合格判定问题,为同类复杂空间钢结构的高精度测量检验偏差修正积累了丰富的应用经验。  相似文献   

中国煤矿安全生产水平空间差异与影响因素     

周天墨  陈鹏飞  陈佳林  诸云强  王晓爽  祁彦民  李威蓉  孙凯  王曙  程全英 《地理研究》2022,41(4):1194-1211

基于2001—2019年分省百万吨死亡率,利用泰尔指数、变异系数和地理探测器等对中国煤矿安全生产水平空间差异程度及其驱动因素展开定量化研究,为及时获取区域煤矿安全态势、提升煤矿事故精准预警与防范提供支持。结果显示：① 依据百万吨死亡率可将中国煤矿安全生产水平分为南方区（川云渝贵湘鄂桂赣粤苏浙闽）、东北区（黑吉辽）、西北区（青新甘）、华北区（京冀鲁豫皖）和中北区（晋陕蒙宁）5个区域,各区煤矿安全水平依次升高。② 煤矿安全水平总体差异经历了总体稳定且差异均衡期（2001—2007年）、总体及差异波动上升期（2008—2015年）、总体稳定但区间差异加大期（2016—2019年）3个发展阶段后仍保持缓慢增长态势,区内差异开始缩减但区间差异持续扩大。③ 影响五大区安全水平的因素各异,采掘环境对东北区、西北区和南方区影响大;供需情况和企业管理类指标的变化更易引起东北区、华北区和中北区安全水平变动;监察执法类指标对中北区以外的各区均具有较高的影响力;各区百万吨死亡率对经济环境均产生响应,但指标的影响系数处于中等水平。④ 监察执法、供需情况和经济环境类指标与其他类别指标普遍具有较强的非线性增强效应,通过调整监察执法类指标更易对安全水平变动产生效果。  相似文献