Geochemical and stable isotopic variability within two rivers rising under the same mountain,but belonging to two distant watersheds     

Stanislav Frančišković-Bilinski  Vlado Cuculić  Halka Bilinski  Hermann Häusler  Philipp Stadler 《Chemie der Erde / Geochemistry》2013

Complementary geochemical and stable isotope investigations of the Gorski Kotar karst aquifer system in western Croatia were obtained for the first time, to answer the question whether both studied rivers drain the same aquifer system or not. The two main rivers, the Kupa and the Rje?ina, rise under the same mountain range, but belong to two different watersheds (Black Sea and Adriatic Sea). The karst aquifer of Gorski Kotar is a potentially important source of drinking water for two neighboring countries, Croatia and Slovenia (Central and South Europe), and is strongly influenced by both Mediterranean and continental weather conditions. It is a part of the Dinaric karst, which is “locus typicus” for karst worldwide and one of the most typical karst areas in the world.  相似文献   

Hydrological considerations for dam siting in arid regions: a Saudi Arabian study     

ZEKAI ŞEN  KHALID AL-SUBA'I 《水文科学杂志》2013,58(2):173-186

Abstract

In any dam siting study in arid regions, rainfall records, runoff measurements and their greatest magnitudes are very important. Unfortunately, the data are scarce and, therefore, empirical approaches and charts obtained from similar regions in other parts of the world are necessary for complete applications. The lack of observed data presents the major problem for runoff modelling in arid regions. These regions have characteristically high rainfall intensity and consequent flash floods with large amounts of sediments. Occurrence of rainfall is sporadic, both temporally and spatially, which makes the interpretation of the rainfall-runoff relationship quite difficult. Flood estimations play a significant role in dam siting from the point of view of water availability. This paper presents the basic calculations of floods and sediment amounts that are necessary in dam siting and construction in an arid area by considering the southwestern part of the Kingdom of Saudi Arabia.  相似文献   

Skeletal Microstructures of the Chiton Ischnochiton hakodadensis and a Comparison with the Cambrian Halkieria     

ZHANG Xiaochuan  YAO Jinxian 《《地质学报》英文版》2014,88(5):1378-1387

Halkieria is an Early Cambrian fossil genus with proposed phylogenetic affinities ranging from stem group lophotrochozoan to stem-group aculiferan. Skeletal similarities are often cited as evidence in support of a mollusk interpretation for Halkieria and related Cambrian fossils. The skeletal microstructures of the polyplacophoran mollusk （chiton） Ischnochiton hakodadensis, which bears perinotum elements resembling sclerites of halkieriids and other coeloscleritophoran small shelly fossils （SSFs）, were studied to evaluate the interpretations. There are both similarities and differences between chiton skeletal structures and halkieriid sclerites： 1） the head valve of L hakodadensis and the dorsal shell of Halkieria evangelista share a similar pattern of fine concentric growth lines, but halkieriid dorsal shells lack other polyplacophoran valve characteristics, including V-shaped indentation, radiate ribs; 2） the arrangement of I. hakodadensis perinotum elements in three zones is somewhat similar to the arrangement pattern of halkieriid sclerites; 3） the inner perinotum scales of L hakodadensis （-200 μm in diameter） have a base and a blade, remarkably similar in morphology to halkieriid palmate sclerites （-400 μm in diameter）. However, I. hakodadensis perinotum scales are nearly solid whereas halkieriid sclerites are hollow. These observations add a microstructural dimension to the skeletal comparison between mollusks and halkeriids, and may prove to be useful in resolving the phylogenetic affinity of Halkieria and the Halwaxiidae.  相似文献   

Geochemistry,provenance and tectonic setting of the Late Cambrian–Early Ordovician Seydişehir Formation in the Çaltepe and Fele areas,SE Turkey     

Mehmet Muzaffer Karadağ 《Chemie der Erde / Geochemistry》2014

The major, trace and rare earth element (REE) contents of metapelite (MPL), metapsammite (MPS) and metamarl (MM) samples from the Cambro-Ordovician Seydi?ehir Formation were analyzed to investigate their provenance and tectonic setting. The MPS, MPL, and MM samples have variable SiO₂ concentrations, with average values of 72.36, 55.54, and 20.95 wt%, moderate SiO₂/Al₂O₃ ratios (means of 6.88, 3.23, and 3.80), moderate to high Fe₂O₃ + MgO contents (means of 5.14, 9.55, 3.56 wt%), and high K₂O/Na₂O ratios (means of 3.26, 3.64, 2.90), respectively. On average, the chemical index of alteration (CIA) values of the MPS and the MPL are 65.87 and 71.96, respectively, while the chemical index of weathering (CIW) values are 74.54 and 85.09, respectively. These data record an intermediate to high degree of alteration (weathering) of plagioclase to illite/kaolinite in the samples’ provenance. The chondrite-normalized REE patterns of all the sample groups are similar and are characterized by subparallel light rare earth elements (LREE)-enriched, relatively flat heavy rare earth elements (HREE) patterns with pronounced Eu anomalies (mean of 0.69) and moderate fractionation [average (La/Yb)_N = 8.7]. Plots of sediments in ternary diagrams of La, Th, Sc and elemental ratios (La/Sc, Th/Sc, Cr/Th, Eu/Eu*, La/Lu, Co/Th, La/Sc and Sc/Th), which are critical for determining provenance, and REE patterns indicate that the metaclastic units of the Seydi?ehir Formation were derived dominantly from felsic to intermediate magmatic rocks and not from a mafic source. The La–Sc–Th and Th–Sc–Zr/10 ternary diagrams of the Seydi?ehir Formation are typical of continental island arc/active continental margin tectonic settings. The geologic location and geochemistry of the Seydi?ehir Formation suggest that it was deposited in an Andean-type retroarc foreland basin during the Late Cambrian–Early Ordovician period. The Neoproterozoic intermediate to felsic magmatic rocks and metaclastic sediments with felsic origins of the Sand?kl?–Afyon Basement Complex (SBC) and their equivalent units, which are thought to be overlain by the younger units in the study area, may be the dominant source rocks for the Seydi?ehir Formation.  相似文献   

Generalized Square Conservative Multistep Finite Difference Scheme Incorporating Historical Observations          下载免费PDF全文

GONG Jing  WANG Bin  JI Zhong-Zhen 《大气和海洋科学快报》2013,(4):223-226

In this paper,a multistep finite difference scheme has been proposed,whose coefficients are determined taking into consideration compatibility and generalized quadratic conservation,as well as incorporating historical observation data.The schemes have three advantages:high-order accuracy in time,generalized square conservation,and smart use of historical observations.Numerical tests based on the one-dimensional linear advection equations suggest that reasonable consideration of accuracy,square conservation,and inclusion of historical observations is critical for good performance of a finite difference scheme.  相似文献   

2019年7月17日江苏东南部特大暴雨的 双偏振雷达观测分析     

王坤  王啸华  夏昕  李敏  顾沛澍  彭小燕 《气象科学》2022,42(5):610-621

利用S波段双偏振雷达数据,结合再分析数据、自动气象站、探空和二维闪电探测数据,采用多普勒雷达风场反演和粒子相态识别等方法,分析了2019年7月17日江苏省东南部多站破历史记录的超强降水对流风暴的偏振特征和云微物理特征;并选取了打破当地强降水历史记录如皋站和潞城站,分析了影响两站的对流单体的异同。影响如皋的对流风暴几无闪电活动,对流质心接近地面,上升气流相对较弱。且0 ℃和-35 ℃层间霰粒子数目相对较少,闪电几乎不存在。在融化层以下,由于强烈的暖雨过程,较大的冰相粒子落下并融化和低层雨滴的聚并增长,导致低层雨滴数量迅速增加,带来地面极端强降水。潞城地区雷暴活动明显,影响其对流风暴发展旺盛。-35~0 ℃层存在强烈的上升运动,抬升低层大量的液相粒子通过淞附作用形成的霰,并与高层冰晶不断碰撞,在云层中形成强大的电场,产生强烈的负闪,且在地面产生了极强的降水。这表明融化层以上的冰相微观物理过程,对于降水的发生和增强非常重要。  相似文献   

The Impact of an Abnormal Zonal Vertical Circulation in Autumn of Super El Ni?o Years on Non-tropical-cyclone Heavy Rainfall over Hainan Island     

Fei WANG  Lifang SHENG  Xiadong AN  Haixia ZHOU  Yingying ZHANG  Xiaodong LI  Yigeng DING  Jing YANG 《大气科学进展》2022,39(11):1914-1924

This study reveals a significant positive connection between autumn non-tropical-cyclone heavy rainfall on Hainan Island and the intensity of Eastern Pacific (EP) El Ni?o events. That is, the amount of rainfall in super EP El Ni?o years is more than that in normal EP El Ni?o years. Comparing EP El Ni?o years of different intensities, the cooler sea surface temperature in the northwestern Pacific during super EP El Ni?o years stimulates a negative surface latent heat flux (LHF) anomaly and abnormal anticyclonic circulation at 850 hPa. Under these conditions, an abnormal zonal vertical circulation develops in the northern South China Sea once a positive LHF anomaly and abnormal cyclonic circulation (ACC) at 850 hPa occur in the Beibu Gulf. The abnormal zonal vertical circulation further strengthens the ascending motion over Hainan Island, as the critical factor that leads to excessive rainfall. Further analysis shows that the positive LHF anomaly, which can be attributed to the increased latent heat transfer which resulted from the increased surface wind speed, is an important trigger for the ACC. However, the ACC is also the supplier of favorable moisture conditions because it intensifies vapor convergence over Hainan Island and meridionally transports moisture from the South China Sea to northeastern Hainan Island, thereby generating heavy rainfall. This paper emphasizes that the impact of El Ni?o events, especially super El Ni?o events, on rainfall over Hainan Island cannot be ignored, even if the traditional view is that frequent rainfall occurs mainly in La Ni?a years.  相似文献   

Toward Understanding the Extreme Floods over Yangtze River Valley in June?July 2020: Role of Tropical Oceans※     

Shaolei TANG  Jing-Jia LUO  Jiaying HE  Jiye WU  Yu ZHOU  Wushan YING 《大气科学进展》2021,38(12):2023-2039,中插8-中插11

The extreme floods in the Middle/Lower Yangtze River Valley (MLYRV) during June?July 2020 caused more than 170 billion Chinese Yuan direct economic losses. Here, we examine the key features related to this extreme event and explore relative contributions of SST anomalies in different tropical oceans. Our results reveal that the extreme floods over the MLYRV were tightly related to a strong anomalous anticyclone persisting over the western North Pacific, which brought tropical warm moisture northward that converged over the MLYRV. In addition, despite the absence of a strong El Ni?o in 2019/2020 winter, the mean SST anomaly in the tropical Indian Ocean during June?July 2020 reached its highest value over the last 40 years, and 43％ (57％) of it is attributed to the multi-decadal warming trend (interannual variability). Based on the NUIST CFS1.0 model that successfully predicted the wet conditions over the MLYRV in summer 2020 initiated from 1 March 2020 (albeit the magnitude of the predicted precipitation was only about one-seventh of the observed), sensitivity experiment results suggest that the warm SST condition in the Indian Ocean played a dominant role in generating the extreme floods, compared to the contributions of SST anomalies in the Maritime Continent, central and eastern equatorial Pacific, and North Atlantic. Furthermore, both the multi-decadal warming trend and the interannual variability of the Indian Ocean SSTs had positive impacts on the extreme floods. Our results imply that the strong multi-decadal warming trend in the Indian Ocean needs to be taken into consideration for the prediction/projection of summer extreme floods over the MLYRV in the future.  相似文献   

The vertical structure of the F ring of Saturn from ring-plane crossings     

Britt R. Scharringhausen  Philip D. Nicholson 《Icarus》2013

We present a photometric model of the rings of Saturn which includes the main rings and an F ring, inclined to the main rings, with a Gaussian vertical profile of optical depth. This model reproduces the asymmetry in brightness between the east and west ansae of the rings of Saturn that was observed by the Hubble Space Telescope (HST) within a few hours after the Earth ring-plane crossing (RPX) of 10 August 1995. The model shows that during this observation the inclined F ring unevenly blocked the east and west ansae of the main rings. The brightness asymmetry produced by the model is highly sensitive to the vertical thickness and radial optical depth of the F ring. The F-ring model that best matches the observations has a vertical full width at half maximum of 13 ± 7 km and an equivalent depth of 10 ± 4 km. The model also reproduces the shape of the HST profiles of ring brightness vs. distance from Saturn, both before and after the time of ring-plane crossing. Smaller asymmetries observed before the RPX, when the Earth was on the dark side of the rings, cannot be explained by blocking of the main rings by the F ring or vice versa and are probably instead due to the intrinsic longitudinal variation exhibited by the F ring.  相似文献   

Study on The Prediction Method of Characteristic Parameters of Solar X-ray Flares     

Guo Ce  Xue Bing-sen  Lin Zhao-xiang 《Chinese Astronomy and Astrophysics》2013

Solar ?ares are important events for the space weather. The predic- tion of relevant parameters of solar ?ares has practical signi?cance for evaluating the effect of sudden ionospheric disturbance (SID). The data of soft X-ray ?ux observed by the GOES-8 satellite in the 23th solar cycle are used to predict the peak intensities and ending times of X-class ?ares with the method of data ?t- ting. Using this method to analyze the X-class ?ares in the 23th solar cycle, it is possible to predict the peak ?ux of an X-class ?are 17 minutes in advance at most. And the ending time of an X-class ?are may be predicted about 60 minutes in advance at most. The predicted results indicate that the prediction method has certain effectiveness and applicability.  相似文献