Modeling of climate change impacts on Lake Burullus,coastal lagoon (Egypt)     

《国际泥沙研究》2021,36(6):756-769

Coastal lagoons are particularly vulnerable to climate change, in particular, Sea Level Rise (SLR) due to their shallowness. Lake Burullus provides a variety of socio-economic services as the second largest coastal lagoon in Egypt. Recently, it has experienced significant ecological deterioration. Thus, its ecosystem is fragile in the face of anthropogenic induced changes. The main objective of the current study is to investigate the climate change impacts on characteristics of Lake Burullus. A depth averaged hydro-ecological modeling system, MIKE21, was applied to develop an eco - hydrodynamic model for the lake. The developed model was calibrated and verified for two successive years: July 2011–June 2012 and July 2012–June 2013. The model simulations exhibited good agreement with the measurements during the calibration and verification processes. Six different Regional Climate Models (RCMs) were compared, using six different statistical metrics, to determine the most accurate one for the study area. The required meteorological input, including surface air temperature, precipitation, and evaporation were derived from the selected RCM. The meteorological input was extracted for two different years in the 21 ^st century considering one Representative Concentration Pathways (RCPs) scenario, based on the Intergovernmental Panel on Climate Change (IPCC) 5th Report. Regional SLR projections for the Mediterranean Sea for the selected RCP scenario and the two studied years were obtained. These future climate change estimates were used to modify the validated model of the lake. A sensitivity analysis was applied to assess effect of future climatic conditions and SLR, separately. The results revealed that the lake water depths will increase and it will be warmer and more saline. Significant spatial variability of the studied parameters under climate change forcing is expected. Consequently, climate change is going to restrict the lake's ability to preserve the present-day species. An urgent management plan involving adaptation works, should be implemented to reduce such potential species losses in Egyptian lagoons.  相似文献   

Mechanism of collision model for bedload transport     

Chenwei Zhao 《国际泥沙研究》2021,36(5):577-581

The current study introduces a new particle–particle collision model as well as a classical particle–wall collision model to simulate the process of bedload transport. Large eddy simulation and two-way coupling Lagrangian point–particle models also are applied. Flow conditions for all simulations are done based on previous experiments and four comparison cases are studied. The bedload function result obtained using this model agrees with the previous studies, which proves that the model is reasonable and effective in dealing with bedload transport in turbulent flow. Otherwise, failure to consider the particle–particle collision, Basset force, or Saffman lift force in the model lead to underestimating the bedload transport rate.  相似文献   

Interfacial instability of sand patterns induced by turbulent shear flow   总被引：1，自引：0，他引：1  

Sk Zeeshan Ali  Subhasish Dey 《国际泥沙研究》2021,36(4):449-456

When a turbulent shear flow above a plane sand surface entrains sand grains,it generates a variety of sand patterns.Fluvial sand forms two major interfacial patterns:meso-scale dunes and antidunes,and large-scale bars.Measurements have evidenced that under erosive conditions,meso-scale patterns either change to or coexist with large-scale patterns.However,it remains elusive what exactly drives the switching of interfacial patterns and how the switching occurs.Here,we showdcombing a flow model with a grain transport model,allowing for both the surface and suspended sand fluxes dthat the switching of patterns emerges from the shear-driven complex feedback between grain transport and topographic perturbations.The switching predominantly depends on the magnitudes of the Rouse number and the grain size to undisturbed flow depth ratio.The model offers quantitative predictions of the maximum amplification of sand patterns and unveils a new attraction erepulsion phenomenon.  相似文献   

广州城市交通系统与空间格局互动影响研究   总被引：3，自引：2，他引：1  

毛蒋兴  闫小培 《地理与地理信息科学》2004,20(6):76-80

该文在评述国内外相关研究的基础上,阐释城市交通系统与空间格局之间的互动影响关系。对广州城市交通系统与空间格局之间的互动影响关系的研究结果表明：广州城市交通系统的发展对空间格局的形成与发展有引导作用;城市空间格局的变化会产生反馈作用,客观上影响着交通系统的空间布局,两者之间存在—个互动反馈作用环。  相似文献   

青藏高原大气水汽收支特征及影响     

柏晶瑜  徐祥德 《地理学报(英文版)》2004,14(1)

Based on 1961-2000 NCEP/NCAR monthly mean reanalysis datasets, vapor transfer and hydrological budget over the Tibetan Plateau are investigated. The Plateau is a vapor sink all the year round. In summer, vapor is convergent in lower levels (from surface to 500 hPa) and divergent in upper levels (from 400 to 300 hPa), with 450 hPa referred to as level of non-divergence. Two levels have different hydrologic budget signatures: the budget is negative at the upper levels from February to November, i.e., vapor transfers from the upper levels over the plateau; as to the lower, the negative (positive) budget occurs during the winter (summer) half year. Evidence also indicates that Tibetan Plateau is a "vapor transition belt", vapor from the south and the west is transferred from lower to upper levels there in summer, which will affect surrounding regions, including eastern China, especially, the middle and lower reaches of the Yangtze. Vapor transfer exerts significant influence on precipitation in summertime months. Vapor transferred from the upper layers helps humidify eastern China, with coefficient -0.3 of the upper budget to the precipitation over the middle and lower reaches of the Yangtze (MLRY); also, vapor transferred from east side (27.5°-32.5°N) of the upper level has remarkable relationship with precipitation, the coefficient being 0.41. The convergence of the lower level vapor has great effects on the local precipitation over the plateau, with coefficient reaching 0.44, and the vapor passage affects the advance and retreat of the rainbelt. In general, atmospheric hydrologic budget and vapor transfer over the plateau have noticeable effects on precipitation of the target region as well as the ambient areas.  相似文献   

Summer season variability of the north residual cap of Mars as observed by the Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES)     

W.M. Calvin  T.N. Titus 《Planetary and Space Science》2008,56(2):212-226

Previous observations have noted the change in albedo in a number of North Pole bright outliers and in the distribution of bright ice deposits between Mariner 9, Viking, and Mars Global Surveyor (MGS) data sets. Changes over the summer season as well as between regions at the same season (L_s) in different years have been observed. We used the bolometric albedo and brightness temperature channels of the Thermal Emission Spectrometer (TES) on the MGS spacecraft to monitor north polar residual ice cap variations between Mars years and within the summer season for three northern Martian summers between July 1999 and April 2003. Large-scale brightness variations are observed in four general areas: (1) the patchy outlying frost deposits from 90 to 270°E, 75 to 80°N; (2) the large “tail” below the Chasma Boreale and its associated plateau from 315 to 45°E, 80 to 85°N, that we call the “Boreale Tongue” and in Hyperboreae Undae; (3) the troughed terrain in the region from 0 to 120°E longitude (the lower right on a polar stereographic projection) we have called “Shackleton's Grooves” and (4) the unit mapped as residual ice in Olympia Planitia. We also note two areas which seem to persist as cool and bright throughout the summer and between Mars years. One is at the “source” of Chasma Boreale (∼15°E, 85°N) dubbed “McMurdo”, and the “Cool and Bright Anomaly (CABA)” noted by Kieffer and Titus 2001. TES Mapping of Mars’ north seasonal cap. Icarus 154, 162-180] at ∼330°E, 87°N called here “Vostok”. Overall defrosting occurs early in the summer as the temperatures rise and then after the peak temperatures are reached (L_s∼110) higher elevations and outlier bright deposits cold trap and re-accumulate new frost. Persistent bright areas are associated with either higher elevations or higher background albedos suggesting complex feedback mechanisms including cold-trapping of frost due to albedo and elevation effects, as well as influence of mesoscale atmospheric dynamics.  相似文献   

Identification of a new outflow channel on Mars in Syrtis Major Planum using HRSC/MEx data     

N. Mangold  V. Ansan  D. Baratoux  F. Costard  L. Dupeyrat  H. Hiesinger  Ph. Masson  G. Neukum  P. Pinet 《Planetary and Space Science》2008,56(7):1030-1042

Syrtis Major Planum is a volcanic plain dominated by lava flows. High resolution stereo camera (HRSC) images of the northern Syrtis Major region display erosional features such as grooves, teardrop-shaped islands and valleys. These landforms are characteristics of outflow channels seen on Mars, therefore implying that a flood event took place in this region. The flow of 100 km long and a few kilometer wide followed the local slopes in most locations. Maximum flood discharges estimated from images and topography vary from about 0.3×10⁶ to 8×10⁶ m³/s, and therefore are in the range of terrestrial mega-floods in the Scablands or Lake Bonneville. In North Syrtis Major, the relationships with surrounding lava flows and the timing of the flood coeval to Syrtis Major volcanic activity suggest that it could be related to the subsurface water discharge mobilized by the volcanic activity. The proximity of Noachian age basement rocks 20 km away from the flood and below lava flows might have played a role in its formation and water presence.  相似文献   

The approximation of neutrino heat conduction with neutrino scattering     

A. V. Yudin  D. K. Nadyozhin 《Astronomy Letters》2008,34(3):198-209

We have developed an algorithm for taking into account the neutrino scattering in the approximation of neutrino heat conduction. We show that in the case of incoherent neutrino scattering (e.g., by electrons), the coefficients of the temperature and chemical potential gradients are averaged over the neutrino energy using functions that can be found by numerically solving integral equations. The coherent scattering by free nucleons and atomic nuclei can be described by introducing a transport cross section. We suggest a new method for calculating the neutrino—electron scattering functions that is based on Fermi—Dirac functions of integer indices.  相似文献   

济阳坳陷西部惠民凹陷第三纪火山岩型油藏成藏机理研究   总被引：12，自引：4，他引：8  

初宝杰  向才富  姜在兴  夏斌  于俊峰 《大地构造与成矿学》2004,28(2):201-208

在全面剖析济阳坳陷惠民凹陷第三纪火成岩空间分布规律的基础上 ,对本区火山岩的成藏机理进行了深入研究 ,总结了惠民凹陷火山岩型油气藏的成藏模式。惠民凹陷的主要烃源岩来自于南部的临南洼陷和北部的滋镇洼陷 ,由于本区火成岩主要沿 2个生烃凹陷间隆起带的临邑帚状断裂带展布 ,保证了火山岩带有充足的油源条件。油气运移的输导体系是由渗透性砂岩、断层、裂缝和不整合面的三维空间组合 ,研究区的临邑帚状断裂带、多期发育的裂缝和不整合面对油气向火山岩储层的运移至关重要。储集空间是储层质量好坏的决定因素 ,惠民凹陷的火山岩储层存在各种的原生储集空间 ,同时由于次生的断层活动和火成岩拱张作用形成了丰富的次生储集空间 ,极大地改善了本区火成岩的储层物性 ,是本区形成各类火成岩圈闭和油藏的保证。本区火成岩存在 3种类型的油气藏 ,即火成岩作为储层、火成岩作为盖层或遮挡层以及火成岩侵入动力型油气藏  相似文献   

Natural Attenuation of Fuel Hydrocarbon Contaminants:Correlation of Biodegradation with Hydraulic Conductivity in a Field Case Study     

LU Guo-ping~  ZHENG Chun-miao~ 《地球科学进展》2004,19(3):403-408

Two biodegradation models are developed torepresent natural attenuation of fuel－hydrocarbon contaminants as observed in a comprehensive natural-gradient tracer test in a heterogeneous aquifer on the Columbus Air Force Basein Mississippi,USA．The first, a first-order mass loss model,describes the irreversible losses of BTEX and its individual components, i．e．,benzene（B）,toluene（T）,ethyl benzene（E）,and xylene（X）．The second, a reactive pathway model,describe ssequential degradation pathways for BTEX utilizing multiple electron acceptors,including oxygen,nitrate,iron and sulfate,and via methanogenesis．The heterogeneous aquifer is represented by multiple hydraulic conductivity（ K） zones delineated on the basis of numerous flowmeter K measurements．A direct propagation artificial neural network（DPN）is used as an inverse modeling tool to estimate the biodegradation rate constants associated with each of the K zones．In both the mass loss model and the reactive pathway model,the biodegradation rate constants show an increasing trend with the hydraulic conductivity．The finding of correlation between biodegradation kinetics and hydraulic conductivity distributions is of general interest and relevance to characterization and modeling of natural attenuation of hydrocarbons in other petroleum-product contaminated sites．  相似文献