Spatio-temporal variations of δ<Superscript>2</Superscript>H and δ<Superscript>18</Superscript>O in precipitation and shallow groundwater in the Hilly Loess Region of the Loess Plateau,China

Groundwater is of utmost significance to socio-economic development and ecological recovery for the Loess Plateau. However, studies regarding the mechanism governing groundwater recharge over this area appear to be inadequate. This study is to examine the spatio-temporal variations of δ²H and δ¹⁸O in precipitation and shallow groundwater. On the basis of this, the mechanisms governing shallow groundwater recharge were explored. Precipitation and groundwater were sampled monthly from May to October during the period 2004–2006 at 13 sites in the Chabagou Catchment (187 km²). In the Caopingxigou Experimental Watershed (0.1 km²), meteorological variables were observed and rainfall larger than 5 mm was sampled immediately after each rain event. Across the area, 90% of the precipitation occurred from May to September primarily in the form of heavy rains or rainstorms with great spatial variability. There were about 30 localized rains in each year. It was indicated that there existed notable seasonality and pronounced spatial variability in precipitation isotopic compositions. Contributing factors and indications of isotopic compositions, as well as their climatic indications such as monsoon intensities and mixing processes of water vapor, were investigated. The δ²H–δ¹⁸O relation of groundwater was found to be δ²H = 3.22 × δ¹⁸O − 38.1, deviating from the local meteoric water line δ²H = 7.57 × δ¹⁸O + 3.9. The range of δ values in groundwater is shrunken to be 15–21% of that in individual precipitations, and groundwater in the middle reaches shows a wider range of δ values. Isotopic results showed that groundwater originates from precipitation with hydrogen and oxygen isotopic compositions being −69 and −9.7‰, respectively, and most groundwater experiences serious evaporation and adequate mixing with old water during infiltration or percolation in the aerated zone. It was also founded that obvious fluctuations of isotopic compositions in groundwater mainly appear in the middle reaches especially at sites that are close to valleys, suggesting varying sources of groundwater from precipitation, precipitation runoff, isotopically enriched surface water and/or lateral recharge of adjacent groundwater.     

过坝下泄水流中温室气体排放速率的数值模拟

当水流通过泄洪建筑物下泄时,水体中所溶解的温室气体(二氧化碳(CO2)、甲烷(CH4)等)会因为所受压力的瞬间改变而导致溶解度降低,从而造成气液之间传质的发生及水中温室气体的排放.然而,目前对于泄流条件下水中温室气体排放的研究还较为缺乏.鉴于原型观测与模型试验的局限性,本文建立了大坝泄流条件下温室气体排放速率的数学模型...     

深井地震综合观测系统集成

深井地震综合观测中信息系统井下传感器采用数字输出方式,与地面仪器之间基于RS-422方式进行通信;基于Linux操作系统,编写与井下传感器通信控制软件及符合相关行业标准的对外服务软件,并进行相关实验,验证方案的现实可行性.     

中国西北部新疆地区沙漠的形成与演化——Ⅱ.古环境重建(英文)

Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human history periods, this paper reviews the researches and progresses on the development of the sandy deserts in Xinjiang. It pointed out that the features of tectonic structure in Xinjiang had made both the Tarim Basin and the Junggar Basin being influenced greatly by the foehn effects originated from the planetary wind system of westerly, the East Asian ocean-continental monsoon and the topographical mountain-valley winds. The regional patterns of climate and environment since the Quaternary were characterized by the overall persistent drought accompanied by fluctuations in the secondary scale. Formations of aeolian sediments in the basins and at the margins are a potential response to global climate change, particularly the aridification of the Asian hinterland deduced by the uprising of the Tibetan Plateau and its surrounding highlands. For the question about the formation time of the Taklamakan Desert, because the research methods, objects and information carriers used in previous studies are different, there are many disputes in the academic circles at present. Evidences from aeolian deposits/rocks at the edge and in the hinterland of these sandy deserts and their chronological data indicate that an arid climate and land surface aeolian processes have occurred at the edge of the Tarim Basin and its hinterland areas since the Tertiary period. However, the duration time of these processes at mass scale should have begun after the middle Pleistocene and lasted to the Holocene. Occurrence of dune fields in recent 2000 years in the oasis areas should be greatly influenced by human factors.     

华北山区短时段参考作物蒸散量的计算

短时段参考作物蒸散量的估算是研究华北山区小尺度范围内的水分循环和转化的重要环节.因受观测条件的限制,北方半湿润半干旱山区短时段参考作物蒸散量的研究相对较少.本文利用FAO Penman-Monteith公式、FAO Penman修正式和Priestley-Taylor公式对华北山区东台沟小流域观测到的4个月的气象数据进行了逐日的参考作物蒸散量计算,结果显示,FAO Penman修正式的计算值比FAO Penman-Monteith公式的计算值平均偏大16%左右,而且经过统计分析,它们具有很好的相关性,即在代表流域内使用FAO Penman修正式计算出参考作物蒸散量之后,再乘以一个折算系数(如0.84),即可得到与FAO Penman-Monteith公式的计算值较为相近的结果;而Priestley-Taylor公式的计算值与FAO Penman-Monteith公式的计算值相比,差异比较显著.分析其原因,我们认为是由于Priestley-Taylor公式没有考虑空气动力项对参考作物蒸散量的影响.因此,如果在华北山区使用Priestley-Taylor公式计算参考作物蒸散量,必须根据季节对公式中的常数项α重新进行修正.本文通过对2003年8月～2004年8月期间逐日计算得到的ET0(P-T)和ET0(P-M)值进行对比分析后,给出了修正后的不同季节的α值,为华北山区计算作物蒸散量提供了依据.     

A critical overview of pan evaporation trends over the last 50 years

Despite the observed increases in global average temperature, observations across the world show that the rate of pan evaporation at a regional scale has been steadily decreasing over the past 50 years. This is known as the pan evaporation paradox. This paper reviews current reported pan evaporation trends, examines available theoretical explanations about this “paradox”, and discusses current research gaps and priorities. It concludes that: (1) three major potential causes of pan evaporation, solar radiation, vapour pressure deficit (VPD) and wind speed, have been changing in the last 50 years. The magnitude of changes and importance of each of these three causes varies from region to region, as does the pan evaporation trend, although overall there is a decreasing trend. (2) Currently two existing theories explaining the pan evaporation trends have limits and are only valid in some specific regions and seasons. Neither of them provides a fundamental physical-based theory that could be applied everywhere. (3) Further investigations are needed before we can fully understand the global evapotranspiration trend in global warming scenarios.     

OWC在“包头市决策服务质量评价及综合应用业务系统”中的应用

通过OWC控件的应用,实现"包头市气象决策服务质量评价和综合应用业务系统"对包头市气候概况、气候资料的查询,并对灾害性天气预警、气象灾害防御以及农牧业生产提供相关建议。     

武汉一级阶地基坑降水引起土层水位变化及压缩变形研究

武汉一级阶地地层具有典型的二元结构特征,从浅层至深层土体渗透性逐渐增加,在基坑工程开挖降水过程中,随着疏干含水层水位的下降,各层土体水位变化特点各不相同,水位的变化影响着土体固结的压缩变形。采用现场群井抽水试验的方法,通过在抽水试验期间对不同深度含水层水位的观测及不同深度土体沉降的监测,结合各层土体性质及相关理论对武汉一级阶地基坑降水引起的土层水位变化及压缩变形规律进行研究。结果表明,武汉一级阶地基坑降水水位变化存在着明显的时空效应,沉降与水位变化密切相关,且沉降过程中土层中出现架空效应。     

The Energy Transformation and Efficiency of the May 12, 2008 Ms 8.0 Wenchuan Earthquake

<正>The energy transformation and efficiency is now a hot topic among researches of scientific drilling into fault zones(Tanaka et al.,2006;Ma et al.,2006).This study conducted temperature measurements and fault gouge particle analysis of borehole WFSD-1 from the Wenchuan Earthquake Fault Science Drilling Project(WFSD),and discussed the earthquake energy budget.The research progress is illuminated as follows.Through collection and analysis of source time function for the Wenchuan earthquake,this study used triangular