Capabilities of satellite precipitation datasets to estimate heavy precipitation rates at different temporal accumulations          下载免费PDF全文

Ali Mehran  Amir AghaKouchak 《水文研究》2014,28(4):2262-2270

The importance of satellite datasets as alternative sources of precipitation information has been argued in numerous studies. Future developments in satellite precipitation algorithms as well as utilization of satellite data in operational applications rely on a more in‐depth understanding of satellite errors and biases across different spatial and temporal scales. This paper investigates the capability of satellite precipitation data sets with respect to detecting heavy precipitation rates over different temporal accumulations. In this study, the performance of Tropical Rainfall Measuring Mission real time (TRMM‐RT), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks and CPC MORPHing (CMORPH) is compared against radar‐based gauge‐adjusted Stage IV data. The results show that none of the high temporal resolution (3‐h) datasets are ideal for detecting heavy precipitation rates. In fact, the detection skill of all products drops as the precipitation thresholds (i.e. 75 and 90 percentiles) increase. At higher temporal accumulations (6, 12 and 24 h), the detection skill improves for all precipitation products, with CMORPH showing a better detection skill compared to all other products. On the other hand, all precipitation products exhibit high false alarm ratios above the heavy precipitation thresholds, although TRMM‐RT lead to a relatively smaller level of false alarms. These results indicate that further efforts are necessary to improve the precipitation algorithms so that they can capture heavy precipitation rates more reliably. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Influence of Penetration Rate and Indenter Diameter in Strength Measurement by Indentation Testing on Small Rock Specimens     

Mohammad Haftani  Bahman Bohloli  Alireza Nouri  Mohammad Reza Maleki Javan  Mahdi Moosavi  Majid Moradi 《Rock Mechanics and Rock Engineering》2015,48(2):527-534

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Analysis of precipitation extremes with the assessment of regional climate models over the Willamette River Basin,USA     

Andrew Halmstad  Mohammad Reza Najafi  Hamid Moradkhani 《水文研究》2013,27(18):2579-2590

An appropriate, rapid and effective response to extreme precipitation and any potential flood disaster is essential. Providing an accurate estimate of future changes to such extreme events due to climate change are crucial for responsible decision making in flood risk management given the predictive uncertainties. The objective of this article is to provide a comparison of dynamically downscaled climate models simulations from multiple model including 12 different combinations of General Circulation Model (GCM)–regional climate model (RCM), which offers an abundance of additional data sets. The three major aspects of this study include the bias correction of RCM scenarios, the application of a newly developed performance metric and the extreme value analysis of future precipitation. The dynamically downscaled data sets reveal a positive overall bias that is removed through quantile mapping bias correction method. The added value index was calculated to evaluate the models' simulations. Results from this metric reveal that not all of the RCMs outperform their host GCMs in terms of correlation skill. Extreme value theory was applied to both historic, 1980–1998, and future, 2038–2069, daily data sets to provide estimates of changes to 2‐ and 25‐year return level precipitation events. The generalized Pareto distribution was used for this purpose. The Willamette River basin was selected as the study region for analysis because of its topographical variability and tendency for significant precipitation. The extreme value analysis results showed significant differences between model runs for both historical and future periods with considerable spatial variability in precipitation extremes. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Upper‐crustal extension during oblique collision: the Temsamane extensional detachment (eastern Rif,Morocco)     

Guillermo Booth‐Rea  Antonio Jabaloy‐Sánchez  Ali Azdimousa  Lahcen Asebriy  Mercedes Vázquez Vílchez  José Miguel Martínez‐Martínez 《地学学报》2012,24(6):505-512

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The use of GIS and remote sensing for the assessment of waterlogging in the dryland irrigated catchments of Farafra Oasis,Egypt     

Mohammed El Bastawesy  Rafat Ramadan Ali 《水文研究》2013,27(2):206-216

This paper investigates the interplay of the hydrogeological characteristics, soil properties and recent land reclamation projects on the distribution of waterlogging and salinization within the Farafra Oasis. The multi‐temporal remote sensing data and field observations show that new reclaimed areas have been recently cultivated in distant areas from the old agricultural land. These new cultivations have developed widespread waterlogging, seepage channels and soil salinization. Analyses of the Shuttle Radar Topography Mission digital elevation model (DEM) showed that both old and new agricultural areas are located within same closed drainage basin. The fluvial channels of these catchments, which were developed during wet climatic pluvial, have largely been obliterated by the prevailing aridity and often buried under aeolian deposits. However, the new cultivations have been developed on the fingertips of these fluvial channels, while the old fields occupy the low‐level playas. The soil of the new cultivated areas is mainly lithic with a high calcium carbonate content, thus limiting the downward percolation of excess irrigation water and therefore developing perched water table and seepage through the palaeo‐channels. The automatically extracted drainage networks from DEM resemble fluvial patterns and coincide with the seepage channels slowly heading toward old cultivation. The inactive alluvial channels and landforms have to be considered when planning for new cultivation in dryland catchments to better control waterlogging and salinization hazard. It is highly recommended that newly developed seepage channels have to be detected and intercepted before reaching old agriculture areas. Therefore, the ‘dry‐drainage’ concept can be implemented as the seepage water can be conveyed into nearby playas reserved for evaporation. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Factors controlling specific sediment yield in the upper Indus River basin,northern Pakistan     

Khawaja Faran Ali  Dirk H. de Boer 《水文研究》2008,22(16):3102-3114

Estimates of sediment yield are essential in water resources analysis, modelling and engineering, in investigations of continental denudation rates, and in studies of drainage basin response to changes in climate and land use. The availability of high resolution, global environmental datasets offers an opportunity to examine the relationships between specific sediment yield (SY_sp) and drainage basin attributes in a geographical information system (GIS) environment. This study examines SY_sp at 14 long‐term gauging stations within the upper Indus River basin. Twenty‐nine environmental variables were derived from global datasets, the majority with a 1 × 1 km resolution. The SY_sp ranges from 194 to 1302 t km^?2 yr^?1 for sub‐basins ranging from 567 to 212 447 km². The high degree of scatter in SY_sp is greatly reduced when the stations are divided into three groups: upper, glacierized sub‐basins; lower, monsoon sub‐basins; and the main Indus River. Percentage snow/ice cover (LC_s) emerges as the single major land cover control for SY_sp in the high mountainous upper Indus River basin. A regression model with percentage snow/ice cover (LC_s) as the single independent variable explains 73·4% of the variance in SY_sp for the whole Indus basin. A combination of percentage snow/ice cover (LC_s), relief and climate variables explains 98·5% of the variance for the upper, glacierized sub‐basins. For the lower monsoon region, a regression model with only mean annual precipitation (P) explains 99·4% of the variance. Along the main Indus River, a regression model including just basin relief (R) explains 92·4% of the variance in SY_sp. Based on the R²_adj and P‐value statistics, the variables used are capable of explaining the majority of variance in the upper Indus River basin. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Vertical distribution and mobilization of arsenic in shallow alluvial aquifers of Chapai-Nawabganj district, Northwestern Bangladesh     

A. H. M. Selim Reza  Jiin-Shuh Jean 《Journal of the Geological Society of India》2012,80(4):531-538

Core sediments from two boreholes and groundwater from fifty four As-contaminated well waters were collected in the Chapai-Nawabganj area of northwestern Bangladesh for geochemical analysis. Groundwater arsenic concentrations in the uppermost aquifer (10 to 40 m of depth) range from 2.76?C315.15 mg/l (average 48.81 mg/l). Arsenic concentration in sediments ranges from 3.26?C10 mg/kg. Vertical distribution of arsenic in both groundwater and sediments shows that maximum As concentration (462 mg/l in groundwater and 10 mg/kg in sediments) occurs at a depth of 24 m. In January 2008, 2009 and 2010, maximum As concentration occurs at the same depth. Environmental scanning electron microscope (ESEM) with EDAX was used to investigate the presence of major and trace elements in the sediments. The dominant groundwater type is Ca-HCO₃ with high concentrations of As and Fe, but with low levels of NO₃ ^? and SO₃ ^?2. Statistical analysis clearly shows that As is closely associated with Fe (R² = 0.64) and Mn (R² = 0.91) in sediments while As is not correlated with Fe and Mn in groundwater samples. Comparatively low Fe and Mn concentrations in some groundwater, suggest that probably siderite and/or rhodochrosite precipitated as secondary mineral on the surface of the sediment particles. The correlations along with results of sequential leaching experiments suggest that reductive dissolution of FeOOH and MnOOH mediated by anaerobic bacteria represents mechanism for releasing arsenic into the groundwater.  相似文献   

An investigation into the fault patterns in the Chadegan region, west Iran: Evidence for dextral brittle transpressional tectonics in the Sanandaj-Sirjan Zone     

Abbas Babaahmadi  Mohammad MohajjelAbbas Eftekhari  Ali Reza Davoudian 《Journal of Asian Earth Sciences》2012,43(1):77-88

The NW-SE trending Sanandaj-Sirjan Zone (SSZ) is the internal part of the Zagros continental collision zone, which mainly consists of metamorphic rocks deformed in a dextral transpressional zone. This dextral transpression is attributed to brittle deformation related to late Cenozoic Arabia-Eurasia oblique continental collision. Major NW-trending faults, including the Dalan, Garmdareh, Yasechah, Sheida, and Ben faults, are reverse faults with a dextral strike-slip component. These faults were displaced by NW-trending synthetic and NE-trending antithetic faults. There are also E-trending thrusts and N-trending normal faults developing in directions that are, respectively, almost normal and parallel to the major shortening direction. The NW-trending Ben, Yasechah, and Sheida faults are NE-dipping faults, and the Dalan and Garmdareh faults are SW-dipping faults. These faults indicate the presence of a transpressive flower structure zone that probably led to the exhumation of Jurassic high-grade metamorphic rocks, such as eclogite, in the central part of the study area.  相似文献   

Review: Groundwater flow and transport modeling of karst aquifers, with particular reference to the North Coast Limestone aquifer system of Puerto Rico   总被引：7，自引：2，他引：5  

Reza Ghasemizadeh  Ferdinand Hellweger  Christoph Butscher  Ingrid Padilla  Dorothy Vesper  Malcolm Field  Akram Alshawabkeh 《Hydrogeology Journal》2012,20(8):1441-1461

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Composition, age, and origin of the ~620?Ma Humr Akarim and Humrat Mukbid A-type granites: no evidence for pre-Neoproterozoic basement in the Eastern Desert, Egypt     

Kamal A. Ali  Abdel-Kader M. Moghazi  Ayman E. Maurice  Sayed A. Omar  Qiang Wang  Simon A. Wilde  Ewais M. Moussa  William I. Manton  Robert J. Stern 《International Journal of Earth Sciences》2012,101(7):1705-1722

The Humr Akarim and Humrat Mukbid plutons, in the central Eastern Desert of Egypt, are late Neoproterozoic post-collisional alkaline A-type granites. Humr Akarim and Humrat Mukbid plutonic rocks consist of subsolvus alkali granites and a subordinate roof facies of albite granite, which hosts greisen and Sn–Mo-mineralized quartz veins; textural and field evidence strongly suggest the presence of late magmatic F-rich fluids. The granites are Si-alkali rich, Mg–Ca–Ti poor with high Rb/Sr (20–123), and low K/Rb (27–65). They are enriched in high field strength elements (e.g., Nb, Ta, Zr, Y, U, Th) and heavy rare earth elements (La _n /Yb _n ?=?0.27–0.95) and exhibit significant tetrad effects in REE patterns. These geochemical attributes indicate that granite trace element distribution was controlled by crystal fractionation as well as interaction with fluorine-rich magmatic fluids. U–Pb SHRIMP zircon dating indicates an age of ~630–620?Ma but with abundant evidence that zircons were affected by late corrosive fluids (e.g., discordance, high common Pb). εNd at 620?Ma ranges from +3.4 to +6.8 (mean?=?+5.0) for Humr Akarim granitic rocks and from +4.8 to +7.5 (mean?=?+5.8) for Humrat Mukbid granitic rocks. Some slightly older zircons (~740?Ma, 703?Ma) may have been inherited from older granites in the region. Our U–Pb zircon data and Nd isotope results indicate a juvenile magma source of Neoproterozoic age like that responsible for forming most other ANS crust and refute previous conclusions that pre-Neoproterozoic continental crust was involved in the generation of the studied granites.  相似文献