Groundwater recharge in suburban areas of Hanoi,Vietnam: effect of decreasing surface-water bodies and land-use change     

Kuroda  Keisuke  Hayashi  Takeshi  Do  An Thuan  Canh  Vu Duc  Nga  Tran Thi Viet  Funabiki  Ayako  Takizawa  Satoshi 《Hydrogeology Journal》2017,25(3):727-742

Over-exploited groundwater is expected to remain the predominant source of domestic water in suburban areas of Hanoi, Vietnam. In order to evaluate the effect on groundwater recharge, of decreasing surface-water bodies and land-use change caused by urbanization, the relevant groundwater systems and recharge pathways must be characterized in detail. To this end, water levels and water quality were monitored for 3 years regarding groundwater and adjacent surface-water bodies, at two typical suburban sites in Hanoi. Stable isotope (δ¹⁸O, δD of water) analysis and hydrochemical analysis showed that the water from both aquifers and aquitards, including the groundwater obtained from both the monitoring wells and the neighboring household tubewells, was largely derived from evaporation-affected surface-water bodies (e.g., ponds, irrigated farmlands) rather than from rivers. The water-level monitoring results suggested distinct local-scale flow systems for both a Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA). That is, in the case of the HUA, lateral recharge through the aquifer from neighboring ponds and/or irrigated farmlands appeared to be dominant, rather than recharge by vertical rainwater infiltration. In the case of the PCA, recharge by the above-lying HUA, through areas where the aquitard separating the two aquifers was relatively thin or nonexistent, was suggested. As the decrease in the local surface-water bodies will likely reduce the groundwater recharge, maintaining and enhancing this recharge (through preservation of the surface-water bodies) is considered as essential for the sustainable use of groundwater in the area.

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Climate-growth relationships of subalpine fir (Abies fargesii) across the altitudinal range in the Shennongjia Mountains, central China   总被引：1，自引：0，他引：1  

Haishan Dang  Yanjun Zhang  Kerong Zhang  Mingxi Jiang  Quanfa Zhang 《Climatic change》2013,117(4):903-917

Dendroecological techniques were employed to explore the growth response of subalpine fir (Abies fargesii) to climatic conditions across its altitudinal range in both the north and south aspects in the Shennongjia Mountains, central China. Correlation function analyses indicated that temperatures in current summer were significantly negatively correlated with fir radial growth at the lower limits, while temperatures in previous autumn and in current spring showed significantly positive correlations with fir radial growth at the mid- and high-elevations in both aspects. Radial growth of the subalpine fir was significantly and positively influenced by precipitation in previous autumn and in current spring at the lower elevations and by precipitation in current spring at the mid-elevations, while precipitation had no significant effects on its radial growth at the upper elevations. Moving correlation functions showed that temperatures in early spring of the current year (i.e., February-April) had a relatively stable effect on tree growth over time at the mid- and upper-elevations in both aspects. Thus, the growth of the subalpine fir responded differently to climatic conditions along the altitudinal gradient, showing that the importance of temperatures for the fir radial growth increased while the importance of precipitation decreased with increasing altitude in both aspects in the Shennongjia Mountains, central China.  相似文献   

辽宁省夏季多模式降水预报检验及晴雨预报技术研究     

聂安祺  李得勤  滕方达  陆井龙  王当 《气象与环境学报》2020,36(5):10-17

利用辽宁省291个国家气象观测站的降水资料,对2019年夏季（6-9月）8种模式降水预报及中央气象台格点降水预报进行了检验评估和比较,并采用消空方法进行晴雨预报技术研究。结果表明：2019年,EC模式具有最优的暴雨预报性能,而日本模式暴雨TS评分最高;中尺度模式对于局地性暴雨和短时强降水具有较好的预报潜力,性能较好的是GRAPES_MESO模式和睿图东北3 km模式;全球模式对24 h暴雨的预报频率比实况偏低30%,3 h强降水则偏低60%,中尺度模式对24 h暴雨的预报频率比实况偏高30%,3 h强降水则偏低20%。由于对小量级降水存在较多空报,各模式原始预报的晴雨预报大多呈现空报偏多的情况;使用小量级降水剔除的消空策略能够明显提高晴雨准确率,消空之后EC模式具有最优的晴雨预报性能。分别使用24 h和3 h累计降水量优化消空策略,发现分别取1.0 mm和0.8 mm的阈值进行消空可以使24 h晴雨准确率提高15.58%,3 h晴雨准确率提高10%-30%。  相似文献   

热带季节内振荡与影响广西的热带气旋生成发展的联系     

覃卫坚  党国花 《气象研究与应用》2020,(1):1-5

利用1978-2013年美国NOAA逐候MJO指数和中国气象局上海台风研究所热带气旋资料,研究了MJO与影响广西热带气旋发生发展的联系。结果表明,当MJO处于非洲大陆和西印度洋时,热带气旋生成区域上空为异常东风带;而当MJO处于西太平洋时,热带气旋生成区域北侧为东风异常带、南侧为西风异常带,有利于季风槽或气旋性环流加强,导致影响广西热带气旋频数偏多。当MJO处于东印度洋时,南海上空风场存在明显的向南分量,热带气旋生成数少、位置偏南;而当MJO处于东太平洋时,热带西太平洋对流受到抑制,导致影响广西热带气旋偏少。  相似文献   

The Cenozoic on-shore basins of Northern Vietnam: Biostratigraphy,vertebrate and invertebrate faunas     

Madelaine Böhme  Jérôme Prieto  Simon Schneider  Nguyen Viet Hung  Do Duc Quang  Dang Ngoc Tran 《Journal of Asian Earth Sciences》2011,40(2):672-687

A first account of paleontological data from three Cenozoic on-shore basins in Northern Vietnam, i.e. the Na Duong, Cao Bang, and Hang Mon basins, reveals a rich fossil fauna and flora of supposed Oligocene age, offering a great potential for taxonomic, paleoenvironmental, and paleobiogeographic studies. Two excavation campaigns unearthed well-preserved fossil remains of mammals, crocodiles, at least six turtle species, some 20 fish taxa, some other 20 mollusc species, and different plant remains. The majority of these taxa are regarded as new to science. However, close affinities to modern faunas of northern Southeast Asia demonstrate the importance of these fossils for an evaluation of the biological history of this modern biodiversity hot spot. Moreover, the fossil assemblages may help to disentangle the intricate Cenozoic tectonic evolution of Southeast Asia by application of paleobiogeographic modelling. Finally, the discovery of complex paleo-food-webs and the presence of several taxa indicative of certain ecological conditions provide a solid base for autecologic, synecologic and paleoclimatic studies. The potential biostratigraphic value of the macrofauna has to be demonstrated yet, as evolutionary concepts for most of the respective groups have not been proposed to date.  相似文献   

地理信息系统图例库的研究   总被引：7，自引：1，他引：6  

党安荣  乔彦友 《地理科学》1996,16(4):370-376

图例库是地理信息系统（ＧＩＳ）的有机组成部分,开发灵活实用的图例库是研制ＧＩＳ软件的重要内容之一,关系到ＧＩＳ成果图形表达的科学性。借鉴ＩＮＴＥＲＧＲＡＰＨ／ＩＧＤＳ的图例库设计思想,引入“符合集合”及“操作函数”的概念,从图例库的基本内涵、实体内容及主要操作等几方面论述了作者对图例库的研究成果。  相似文献   

五台山变质地体的区域变质相带和变质期次   总被引：5，自引：2，他引：5  

党修鹏 《岩石学报》1993,9(1):55-69

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A Study on the Dissolution Kinetics of Basalt—Water Interaction under Different pH Conditions I：Release of Elements and pH Neutralization Effect     

党志  侯英 《中国地球化学学报》1993,12(2):183-191

Experimental research on the chemical weathering of alkaline-olivine basalt from Huangyi Mountain,Kuandain County,Liaoning.Province and olivine basalt from Dayangke,Mingxi County,Fujian Province has shown that the acidity of the solution tends to become neutral regardless of what the acidity of the starting solution would be during basalt0-water interaction.We call this phenome-non“pH neutralized Effect”.The dissolved species in the solution were determined and unreacted and reacted sample-surface chemical components involved or uninvolved in reaction were analyzed using X-ray photoelectron spectroscopy(XPS).The results revealed two different mechanisms of dissolution of basalt in acidic and basic solutions.  相似文献   

8805号登陆台风特大暴雨的数值模拟   总被引：3，自引：1，他引：3  

张福青  蒋全荣  党人庆 《热带气象学报》1996,12(3):257-264

应用中尺度模式ＭＭ４,使用了一种简单的模式台风处理方法,成功地模拟了８８０５号台风登陆前后的演变及其伴随的特五暴雨过程,即对分析的台风中心物理量场进行修正而形成与实况极为一致的初值,以期能更好地模拟台风过程。从模拟结果可以看出,台风降水强度中心基本上是随台风登陆移动而变化的,每一时期的降水中心基本上与台风移动的路径一致或略偏前方,在登陆时的降水最大,这种降水变化与台风上升运动的烛一致的,上升运动越  相似文献   

On-Going Galaxy Formation     

Jonathan Braine  P.-A. Duc  U. Lisenfeld  V. Charmandaris  O. Vallejo  S. Leon  E. Brinks 《Astrophysics and Space Science》2002,281(1-2):407-408

We investigate the process of galaxy formation as can be observed in the only currently forming galaxies - the so-called Tidal Dwarf Galaxies, hereafter TDGs - through observations of the molecular gas detected via its CO (Carbon Monoxide) emission. These objects are formed of material torn off of the outer parts of a spiral disk due to tidal forces in a collision between two massive galaxies. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of gas and a bona fide galaxy. We have detected CO in 8 TDGs (Braine, Lisenfeld, Duc and Leon, 2000: Nature 403, 867; Braine, Duc, Lisenfeld, Charmandaris, Vallejo, Leon and Brinks: 2001, A&A 378, 51), with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few 10⁸ M _⊙. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular gas masses is observed, in accord with the transformation of HI into H₂. Although TDGs share many of the properties of small irregulars, their CO luminosity is much greater (factor ∼ 100) than that of standard dwarf galaxies of comparable luminosity. This is most likely a consequence of the higher metallicity (≳sim 1/3 solar) of TDGs which makes CO a good tracer of molecular gas. This allows us to study star formation in environments ordinarily inaccessible due to the extreme difficulty of measuring the molecular gas mass. The star formation efficiency, measured by the CO luminosity per Hα flux, is the same in TDGs and full-sized spirals. CO is likely the best tracer of the dynamics of these objects because some fraction of the HI near the TDGs may be part of the tidal tail and not bound to the TDG. Although uncertainties are large for individual objects, as the geometry is unknown, our sample is now of eight detected objects and we find that the ‘dynamical’ masses of TDGs, estimated from the CO line widths, seem not to be greater than the ‘visible’ masses (HI + H₂ + a stellar component). Although higher spatial resolution CO (and HI) observations would help reduce the uncertainties, we find that TDGs require no dark matter, which would make them the only galaxy-sized systems where this is the case. Dark matter in spirals should then be in a halo and not a rotating disk. Most dwarf galaxies are dark matter-rich, implying that they are not of tidal origin. We provide strong evidence that TDGs are self-gravitating entities, implying that we are witnessing the ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas, which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献