Sea Level Changes Along Bangladesh Coast in Relation to the Southern Oscillation Phenomenon   总被引：1，自引：1，他引：0  

O. P. Singh Tariq Masood Ali Khan  Tad S. Murty  Md. Sazedur Rahman 《Marine Geodesy》2013,36(1):65-72

Interannual variations of sea level along the Bangladesh coast are quite pronounced and often dominate the long-term sea level trends that are taking place. The El Niño/Southern Oscillation (ENSO) induced variation is an important component of interannual mode of variations. The present article deals with the relationship between the sea level variations along the Bangladesh coast and the Southern Oscillation phenomenon. The mean tide level data of monsoon season (June to September) pertaining to Hiron Point (in Sundarbans) and Char Changa (on the mouth of Meghna River) have been analyzed and correlated to the Southern Oscillation Index (SOI). The annual variation of mean tide level in the coastal areas of Bangladesh reveals that the tide level reaches its peak during the monsoon season. The maximum tide level during the calendar year is recorded in August. Thus, it is not surprising that the inundation of the coastal belt of Bangladesh due to the floods is most common during the summer monsoon season, especially from July to September. Therefore, the sea level variations during the monsoon are of paramount importance to Bangladesh. The results of the present study show that both at Hiron Point and Char Changa there is a substantial difference between the mean tide level during the El Niño and La Niña monsoons. The mean tide level at Hiron Point is higher by about 5 cm during August of La Niña years as compared to that during the El Niño years. The difference at Char Changa, which is located at the mouth of Meghna River, is much higher. This is probably due to the increased fresh water discharge into the Meghna River during La Niña years. Thus at the time of crossing of a monsoon depression, the chances of widespread inundation are higher during a La Nin~a year as compared to that during an El Niño year. The Correlation Coefficients (CCs) between Mean Tide Levels (MTLs) at Hiron Point and Char Changa and the SOI during September (at the end of monsoon) are +0.33 and +0.39 respectively. These CCs are statistically significant at 90% and 95% levels, respectively. These results may find applications in the preparedness programs for combating sea level associated disasters in Bangladesh.  相似文献   

Research Note: Full‐waveform inversion of the unwrapped phase of a model     

Tariq Alkhalifah 《Geophysical Prospecting》2014,62(2):397-403

Reflections in seismic data induce serious non‐linearity in the objective function of full‐ waveform inversion. Thus, without a good initial velocity model that can produce reflections within a half cycle of the frequency used in the inversion, convergence to a solution becomes difficult. As a result, we tend to invert for refracted events and damp reflections in data. Reflection induced non‐linearity stems from cycle skipping between the imprint of the true model in observed data and the predicted model in synthesized data. Inverting for the phase of the model allows us to address this problem by avoiding the source of non‐linearity, the phase wrapping phenomena. Most of the information related to the location (or depths) of interfaces is embedded in the phase component of a model, mainly influenced by the background model, while the velocity‐contrast information (responsible for the reflection energy) is mainly embedded in the amplitude component. In combination with unwrapping the phase of data, which mitigates the non‐linearity introduced by the source function, I develop a framework to invert for the unwrapped phase of a model, represented by the instantaneous depth, using the unwrapped phase of the data. The resulting gradient function provides a mechanism to non‐linearly update the velocity model by applying mainly phase shifts to the model. In using the instantaneous depth as a model parameter, we keep track of the model properties unfazed by the wrapping phenomena.  相似文献   

Assessment of Land use/land cover Change in the North-West District of Delhi Using Remote Sensing and GIS Techniques   总被引：1，自引：0，他引：1  

Atiqur Rahman  Sunil Kumar  Shahab Fazal  Masood A Siddiqui 《Journal of the Indian Society of Remote Sensing》2012,40(4):689-697

Land is one of the prime natural resources. A city grows not only by population but also by changes in spatial dimensions. Urban population growth and urban sprawl induced land use changes and land transformation. The land transformation is a natural process and cannot be stopped but it can be regulated. Many geographical changes at the urban periphery are associated with the transfer of land from rural to urban purpose. There is an urgent need for fast growing areas like Delhi, which can be easily done by high-resolution remote sensing data. Land use/land cover of North West of Delhi has been analyzed for the time period of 1972?C2003. The remote sensing data used in study is Aster image of 2003 with a spatial resolution of 15?m and other data of 1972 Survey of India (SOI) toposheet at the scale of 1:50,000. Supervised digital classification using maximum likelihood classifier was applied for preparing land use/land cover. A change detection model was applied in ERDAS Imagine to find out the land use/land cover during 1972 to 2003. Eight land use classes was identified but main dominated classes were built up and agricultural land. A drastic change has been recorded during 30 years of time i. e. (1972-2003). In 1972, 92.06% of the land was under agricultural practice, which reduced to 64.71% in 2003. This shows 27.35% decrease in agricultural land in three decades. On the other hand built up area was 6.31% in 1972, which increased to 34% in 2003. One of the main cause of this land use change is the population growth due to the migration in the district from small cities and rural areas of Delhi.  相似文献   

Bright side? The impacts of Three Gorges Reservoir on local ecological service of soil conservation in southwestern China     

Qinli Xiong  Yang Xiao  Zhiyun Ouyang  Kaiwen Pan  Lin Zhang  Xingjin He  Hua Zheng  Xiaoming Sun  Xiaogang Wu  Akash Tariq  Lingjuan Li 《Environmental Earth Sciences》2017,76(8):323

Three Gorges Reservoir in China was running since June 2003, and its impacts on soil erosion (SE) and soil conservation (SC) have attracted major public attentions. We quantified the soil conservation service of ecosystems in the Three Gorges Reservoir Area (TGRA) based on a GIS platform using the universal soil loss equation. We revealed the changes of spatial and temporal patterns of soil conservation (SC) and soil erosion (SE) after project construction as well as impact factors on local SE and SC. Results showed that the total amounts and mean capacity of soil conservation services in the TGRA were 15.38-billion t a^?1 and 2134.73 t ha^?1 a^?1, respectively. Northeast reservoir area owned better services than the southwest, and the regions with a capacity of >5000 t ha^?1 a^?1 were primary located in mountain areas. An increasing trend in SC appeared in the TRGA and “with increasing SC” totaled 22690.5 km² (38.9%), while the areas “with decreasing SC” amounted to 3460.4 km² (5.9%) between 2000 and 2010. Moreover, the pattern of changing SC was continuous in this area. The spatial characteristics of soil conservation service in the TGRA were primarily affected by slope, climate and terrain features. In addition, the reforestation and/or forest protection would contribute to soil erosion control in the TGRA. The results revealed a great spatial heterogeneity of soil conservation service in this region, which may provide useful suggestions for land management, soil erosion control and ecosystem protection in the TGRA in China.  相似文献   

Observed damages in Pakistan due to 16 April 2013 Iran earthquake     

Muhammad Masood Rafi  Sarosh H. Lodi  Muhammad Ahmed  Naveed Alam 《Bulletin of Earthquake Engineering》2015,13(2):703-724

  相似文献   

An approach to digitize analog form of accelerograms recorded at Tarbela—Pakistan     

M. Rizwan  M. Ilyas  A. Masood  I. Towhata 《Soil Dynamics and Earthquake Engineering》2008,28(4):328-332

Pakistan has a long history of seismological activity. The devastation caused by Kashmir earthquake has been administered all over the world. In Pakistan first seismological network, consisting of analog accelerograms and seismographs, was setup in early 1969 at Tarbela, where the largest water reservoir of the country is located. An approach to convert analog ground motion records into digital form is explained using a simple technique. The digitized data was compared with the original analog record and found in good agreement. The data has been used to plot response spectra. The digitized data will be available for seismic response analysis of structures and seismic risk analysis of the region.  相似文献   

The role of visual saliency in the automation of seismic interpretation          下载免费PDF全文

Muhammad Amir Shafiq  Tariq Alshawi  Zhiling Long  Ghassan AlRegib 《Geophysical Prospecting》2018,66(Z1):132-143

In this paper, we propose a workflow based on SalSi for the detection and delineation of geological structures such as salt domes. SalSi is a seismic attribute designed based on the modelling of human visual system that detects the salient features and captures the spatial correlation within seismic volumes for delineating seismic structures. Using this attribute we cannot only highlight the neighbouring regions of salt domes to assist a seismic interpreter but also delineate such structures using a region growing method and post‐processing. The proposed delineation workflow detects the salt‐dome boundary with very good precision and accuracy. Experimental results show the effectiveness of the proposed workflow on a real seismic dataset acquired from the North Sea, F3 block. For the subjective evaluation of the results of different salt‐dome delineation algorithms, we have used a reference salt‐dome boundary interpreted by a geophysicist. For the objective evaluation of results, we have used five different metrics based on pixels, shape, and curvedness to establish the effectiveness of the proposed workflow. The proposed workflow is not only fast but also yields better results as compared with other salt‐dome delineation algorithms and shows a promising potential in seismic interpretation.  相似文献   

Singularity. A manifesto for incomparable geographies     

Tariq Jazeel 《Singapore journal of tropical geography》2019,40(1):5-21

This paper is a methodological response to the challenge of decolonizing geographical knowledge. It mobilizes post‐ and de‐colonial critiques of geographical knowledge production and conceptual work, suggesting how such work unwittingly disfigures the precise contours of the places and socio‐spatial formations on which geographers work, drawing them into implicit and reductive forms of comparison. Drawing on research and sources from South Asia, the paper moves instead toward more uncertain engagements with, and dispositions to, the production of geographical knowledge; ones attuned to the poetics of planetary difference. The paper speculates on five intellectual and methodological resources, or tactics, aimed toward producing geographical scholarship attuned to the tableaux of heterogeneous and incomparable singularities at large across the world: theory and reading; friction and fragments; translation/untranslatability; abiding by; and poetics.  相似文献   

Web GIS: Implementation issues   总被引：1，自引：0，他引：1  

ZHENG Kou gen  SOOMRO Tariq Rahim PAN Yun he 《中国地理科学(英文版)》2000,10(1):74-79

1　ＩＮＴＲＯＤＵＣＴＩＯＮＷｉｔｈｔｈｅｒａｐｉｄｅｘｐａｎｓｉｏｎａｎｄｄｅｖｅｌｏｐｍｅｎｔｏｆＩｎ ｔｅｒｎｅｔａｎｄＷＷＷ (ＷｏｒｌｄＷｉｄｅＷｅｂｏｒＷｅｂ) ,ＷｅｂＧＩＳ (ＷｅｂＧｅｏｇｒａｐｈｉｃａｌＩｎｆｏｒｍａｔｉｏｎＳｙｓｔｅｍ )ｉｓｂｅ ｃｏｍｉｎｇｅｖｅｒｍｏｒｅｐｏｐｕｌａｒａｎｄａｓａｒｅｓｕｌｔｎｕｍｅｒｏｕｓｓｉｔｅｓｈａｖｅａｄｄｅｄＧＩＳｃａｐａｂｉｌｉｔｙｏｎｔｈｅｉｒＷｅｂｓｉｔｅｓ(ＢＯＳＴＯＮｅｔａｌ .,1994 ;ＰＵＴＺ ,1994 ;ＳＨＩＦＦＥＲ ,1995;ＳＯＶＩ…  相似文献   

Neighboring cage fish farming affecting water and seabed quality of the jordanian northern gulf of aqaba, red sea     

Al-Zibdah Mohammad  Oqaily Firas  Al-Najjar Tariq  Manasrah Riyad 《Ocean Science Journal》2008,43(1):9-16

Environmental qualities of coastal water and bottom sediment were assessed at Jordan's northernmost tip of Gulf of Aqaba to evaluate possible impacts of the bordering fish pen cages in Eilat. Results showed significant differences between surface and bottom water in the chemical and physical variables in the different months of the year (2004-2005). Chlorophyll a was also significantly higher in bottom water when compared to that of the offshore water. Nitrate and ammonia were significantly higher in bottom water than the surface water at each individual station. The upper 2 cm of sediment sample recorded higher values of total phosphorus and organic matter. Seasonality affected the content of total phosphorus, organic matter, redox potential and color especially at the sediment layer below 3 cm of the sediment core. The present investigation showed slight modification of water and sediment qualities but no clear sign of eutrophication was observed. However, to maintain sustainability of healthy environmental conditions at the northern tip of Gulf of Aqaba potentials of any possible environmental risks arising from the fish farms or any other coastal investment should be carefully considered.  相似文献