Observed trends of climate and land cover changes in Lake Baikal basin     

Batsuren Dorjsuren  Denghua Yan  Hao Wang  Sonomdagva Chonokhuu  Altanbold Enkhbold  Davaadorj Davaasuren  Abel Girma  Asaminew Abiyu  Lanshu Jing  Mohammed Gedefaw 《Environmental Earth Sciences》2018,77(20):725

Land cover and vegetation in Lake Baikal basin (LBB) are considered to be highly susceptible to climate change. However, there is less information on the change trends in both climate and land cover in LBB and thus less understanding of the watershed sensitivity and adaptability to climate change. Here we identified the spatial and temporal patterns of changes in climate (from 1979 to 2016), land cover, and vegetation (from 2000 to 2010) in the LBB. During the past 40 years, there was a little increase in precipitation while air temperature has increased by 1.4 °C. During the past 10 years, land cover has changed significantly. Herein grassland, water bodies, permanent snow, and ice decreased by 485.40 km², 161.55 km² and 2.83 km², respectively. However, forest and wetland increased by 111.40 km² and 202.90 km², respectively. About 83.67 km² area of water bodies has been converted into the wetland. Also, there was a significant change in Normalized Difference Vegetation Index (NDVI), the NDVI maximum value was 1 in 2000, decreased to 0.9 in 2010. Evidently, it was in the mountainous areas and in the river basin that the vegetation shifted. Our findings have implications for predicting the safety of water resources and water eco-environment in LBB under global change.  相似文献   

Contribution of cross time-frequency analysis in assessment of possible relationships between large-scale climatic fluctuations and rainfall of northern central Algeria     

Bilel Zerouali  Mohamed Mesbah  Mohamed Chettih  Mohammed Djemai 《Arabian Journal of Geosciences》2018,11(14):392

This paper is proposed for the investigation of possible relationships between the large-scale atmospheric circulation phenomena such as the North Atlantic Oscillation (NAO), Southern Oscillation (SOI), Mediterranean Oscillation (MO), Western Mediterranean Oscillation (WeMO) and rainfall of Sebaou river watershed (Northern central Algeria), covering a period of 39 years at monthly scale. Several time and scale-based methods were used: correlation and spectral analysis (CSA), continuous wavelet transform (CWT), multiresolution wavelet analysis (MRWA), cross wavelet analysis (XWT), wavelet coherence transform (WCT) and cross multiresolution wavelet analysis (CMRWA). The rainfall analysis by CSA and CWT has been clearly demonstrating the dominance of 1 year and 1–3-year modes, which they explain 30 to 51% and 25 to 28% of the variance respectively. However, the indices have shown that inter-annual fluctuations up to long-term explain between 60 and 90%. CWT and MRWA indicated significant fluctuations materialising a dry period more marked between the 1980s and 1990s with strong trend towards drier conditions starting from the 1980s, explained by the decadal components D7 and the approximation A7. In addition to the annual component, the XWT spectrums reveal strong coefficients for the SOI between 1992–2005 and 1986–2000 for the modes of 5–10 years and higher than 10 years respectively and less intense for NAO. The WCT between NAO and rainfall indicated the most significant relationship for 1 year, 1–3 years and 3–5 years approximately from the early 1980s corresponding to the dry period. However, the SOI affects rainfall only locally and with significant values more or less localised in the time-frequency space between MO, WeMO and rainfall, but this influence could be significant for low-frequency events. CWMRA shows that the components of 5–10 years and higher than 10 years are the most effective to represent climate index-rainfall significant relationships, where change in Daubechies wavelet properties can improve the correlation across the scales. Furthermore, has indicated that the short-term processes dominate the relationship index-rainfall, which masks the long-term phenomena whose influence can sometimes be very distant. As such, the rainfall variability of the study area has shown fairly significant links, at least locally with large-scale atmospheric circulation phenomena.  相似文献   

Utilization of ASTER and OLI data for lithological mapping of Nugrus-Hafafit area,South Eastern Desert of Egypt     

Ashraf Emam  Zakaria Hamimi  Abdelhamid El-Fakharani  Ezzat Abdel-Rahman  Juan Gomez Barreiro  Mohammed Y. Abo-Soliman 《Arabian Journal of Geosciences》2018,11(23):756

Lithological discrimination of Neoproterozoic rocks occupying Nugrus-Hafafit area, South Eastern Desert of Egypt, has been carried out using Operational Land Imager (OLI) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensors’ imagery data. The applicable processing enhancement techniques include optimum index factor (OIF), band ratioing, principal component analysis (PCA), and minimum noise fraction (MNF) transform. The area comprises varieties of low-grade metamorphosed ophiolitic mélange and island-arc rocks, thrusting over high-grade metamorphic gneissic core complexes, and intruded by syn-, late-, and post-tectonic granitoids. The OLI band ratio 6/7 discriminates clearly the ophiolitic serpentinites-talc-carbonate rocks, while 4/5 ratio image is able to separate between mafic and felsic rocks. Moreover, the ASTER band ratio 6/8 is used to distinguish the amphibole-bearing rocks, including amphibolite and hornblende gneiss. The OLI and ASTER second principal component (PC2) images reflect the contrast spectral behavior of ophiolitic mélange rocks through visible-near-infrared (VNIR) and shortwave (SWIR) regions. The OLI-PC3 shows the ability to delineate the Fe-rich rocks, including amphibolite and metamafics, while ASTER-PC3 is effective for quartz-feldspathic granites and psammitic gneisses. Visual interpretation and integration of processed data with petrography and field investigation resulted in complete differentiation for the different lithologies and creation of a new detailed geological map of Nugrus-Hafafit area.  相似文献   

Laboratory experiments on three-dimensional deformable granular landslides on planar and conical slopes     

Brian C. McFall  Fahad Mohammed  Hermann M. Fritz  Yibin Liu 《Landslides》2018,15(9):1713-1730

Landslides of subaerial and submarine origin may generate tsunamis with locally extreme amplitudes and runup. While the landslides themselves are dangerous, the hazards are compounded by the generation of tsunamis along coastlines, in enclosed water bodies, and off continental shelves and islands. Tsunamis generated by three-dimensional deformable granular landslides were studied on planar and conical hill slopes in the three-dimensional NEES tsunami wave basin at Oregon State University based on the generalized Froude similarity. A unique pneumatic landslide tsunami generator (LTG) was deployed to control the kinematics and acceleration of the naturally rounded river gravel and cobble landslides to simulate broad ranges of landslide shapes and velocities along the slope. Lateral and overhead cameras are used to measure the landslide shapes and kinematics, while acoustic transducers provide the shape of the subaqueous deposits. The subaerial landslide shape is extracted from the camera images as the landslide propagates under gravity down the hill slope, and surface reconstruction of the landslide is conducted using the stereo particle image velocimetry (PIV) system on the conical hill slope. Subaerial landslide surface velocities are measured with a planar PIV system on the planar hill slope and stereo PIV system on the conical hill slope. The submarine deposits are characterized by the runout distances and the deposit thickness distributions. Larger cobbles are observed producing hummock type features near the maximum runout length. These unique laboratory landslide experiments serve to validate deformable landslide models as well as provide the source characteristics for tsunami generation.  相似文献   

Testing and Modeling the Short-Term Behavior of Lime and Fly Ash Treated Sulfate Contaminated CL Soil   总被引：1，自引：1，他引：0  

Ahmed Mohammed  Cumaraswamy Vipulanandan 《Geotechnical and Geological Engineering》2015,33(4):1099-1114

  相似文献   

Facies architecture and sequence development of the Euphrates formation in western Iraq     

Mohammed F. Al-Ghreri  Amer S. Al-jibouri  Ahmed Asker Al-Ahmed 《Arabian Journal of Geosciences》2014,7(7):2679-2687

The Euphrates formation is widely exposed in western Iraq near Al-Qaim area. It extends eastward parallel to the Euphrates River on both sides, crossing Anah, Hadetha, and Al-Baghdadi vicinities. Based on the benthic foraminiferal assemblages and microfacies features, 12 different microfacies types have been recognized into two Stratigraphic sections that are lime mudstone, wackestone, bioclastic wackestone, miliolids wackestone, alveolinids wackestone, packstone, bioclastic packstone, peloidal packstone, miliolids packstone, peneroplids packstone, rotaliids packstone, grainstone, peloidal grainstone, oolitic grainstone, and miliolids grainstone. Accordingly, the depositional environments were recognized on the basis of microfacies identification and interpretation ranging from restricted marine, shoal, to open marine environments. The exposed Euphrates succession is represented by four fourth-order cycles (A, B, C, and D); they are mostly asymmetrical showing slightly lateral variation in thickness and symmetry. These cycles represent a succession episode of sea level rises and stillstands. The nature of these cycles reflects variation in the relative sea level resulted from eustatic and tectonic subsidence. Cycle A is underlain by SB1 of Sheik Alas formation in Al-Baghdadi section and by Anah formation in Wadi Hjar section. Cycle D is overlain by SB1 of Fatha formation in Al-Baghdadi section and by conformable contact of Nfayil formation in Wadi Hjar section. According to sequence development, the study area shows low rate of subsidence and the major controlling factor that affects eustatic sea level fluctuation.  相似文献   

LA-ICP-MS U-Pb zircon geochronology and Hf isotope,geochemistry and kinetics of the Daxigou anorthosite from Kuruqtagh block,NW China     

Qian Yuan  Xiaofeng Cao  Xinbiao Lü  Xiangdong Wang  Enlin Yang  Yuegao Liu  Banxiao Ruan  Hong Liu  Mohammed Abdalla Adama Munir 《中国地球化学学报》2014,33(3):207-220

Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of the Precambrian evolution of the Tarim Basin. In this paper, we studied the petrology, geochemistry, zircon LA-ICPMS U-Pb chronology and zircon Hf isotope of Daxigou anorthosite （DA） which is located at the northem margin of Tarim craton and discussed the rock formation, tectonic and geological significance. Zircons from the intrusions display oscillatory zoning and high Th/U ratios （0.39-1.35）, implying their magmatic origin. Zircon LA-ICP-MS U-Pb dating results indicate that they formed during the Paleoproterozoic age with the weighted 2~6pb/238U average age of 1818~9 Ma, which is significantly different from former＇s Neoproterozoic age, and is co- incidentally identical with its associated syenite granite age within the error range. Studies on petrogeochemistry suggest that DA belongs to medium-sodium peraluminous alkaline type, rich in Pb, La, Th and LILE, and poor in HFSE （Gd, Nd, and Ta）. The chondrite-normalized REE pattern is slightly to the right form. The average Y~REE is 317.2~ 10-6; HREE show moderate fractionation [average LREE/HREE is 14.71, average （La/Yb）N is 24.77; average （LaJSm）N is 3.85, and average （Gd/Yb）y is 3.46]; and the 6Eu and 8Ce are not obvious. Their initial Hf isotope ratios and Hf two-stage model ages range from -6.6 to -4.43 and 2.63 to 2.74 Ga, respectively. Taken together, it is sug- gested that Daxigou anorthosite is a typical volcanic anorthosite and its primary magma could be contaminated by the partial melt Neoarchaean crust and mainly formed in the arc environment, which recoded the tectonic-magma activities response of the Tarim refers to the amalgamation of the supercontinent Columbia.  相似文献   

Relative performance of CMIP5 and CMIP6 models in simulating rainfall in Peninsular Malaysia     

Pour  Sahar Hadi  Shahid  Shamsuddin  Mainuddin  Mohammed 《Theoretical and Applied Climatology》2022,149(1-2):709-725

Theoretical and Applied Climatology - This study evaluated the skills of global climate models (GCMs) of the fifth and sixth Coupled Model Intercomparison Project (CMIP5 and CMIP6) in simulating...  相似文献   

On the recent global mean sea level changes: Trend extraction and El Niño's impact     

Mahdi Haddad  Habib TaibiSi Mohammed Mohammed Arezki 《Comptes Rendus Geoscience》2013,345(4):167-175

The spatial sampling offered by TOPEX and Jason series of satellite radar altimeters and its continuity during the last twenty years are major assets to provide an improved vision of the global mean sea level (GMSL). The objective of this paper is to examine the recent GMSL variations (1993–2012) and to investigate the correlation between the GMSL and ENSO (El Niño-southern oscillation) episodes. For this purpose, a mean sea level anomalies time series, obtained from TOPEX, Jason-1 and Jason-2 measurements, is used to determine the trend of GMSL changes by using a simplified form of an unobserved components model (namely UCM). Then, to investigate the impact of the ENSO phenomenon on the GMSL changes, we considered the sea surface temperature anomalies (SSTA) index over the Niño3 region (5N–5S 150W–90W). Cross wavelet transform and wavelet coherence analysis are performed to expose common power between the GMSL changes and the SSTA index and their relative phase in the time–frequency space. The results indicate that there are in the estimated GMSL's trend a number of fluctuations over short periods that are least partly related to the El Niño/La Niña episodes. Cross wavelet transform and wavelet coherence analysis indicate that a significant correlation between GMSL and ENSO occurred during 1997–1998, 2006–2007, 2009–2010 El Niño events and 2007–2008 and 2010–2011 La Niña ones. All these areas show in-phase relationship, suggesting that GMSL and SSTA index vary synchronously.  相似文献   

Prediction of settlement trough induced by tunneling in cohesive ground   总被引：1，自引：0，他引：1  

Mohammed Y. Fattah  Kais T. Shlash  Nahla M. Salim 《Acta Geotechnica》2013,8(2):167-179

Surface settlements of soil due to tunneling are caused by stress relief and subsidence due to movement of support by excavation. There are significant discrepancies between empirical solutions to predict surface settlement trough because of different interpretations and database collection by different authors. In this paper, the shape of settlement trough caused by tunneling in cohesive ground is investigated by different approaches, namely analytical solutions, empirical solutions, and numerical solutions by the finite element method. The width of settlement trough was obtained by the finite element method through establishing the change in the slope of the computed settlement profile. The finite element elastic-plastic analysis gives better predictions than the linear elastic model with satisfactory estimate for the displacement magnitude and slightly overestimated width of the surface settlement trough. The finite element method overpredicted the settlement trough width i compared with the results of Peck for soft and stiff clay, but there is an excellent agreement with Rankin’s estimation. The results show that there is a good agreement between the complex variable analysis for Z/D = 1.5, while using Z/D = 2 and 3, the curve diverges in the region faraway from the center of the tunnel.  相似文献