Monitoring cryosphere and associated flood hazards in high mountain ranges of Pakistan using remote sensing technique     

Arshad Ashraf  Rakhshan Roohi  Rozina Naz  Naveed Mustafa 《Natural Hazards》2014,73(2):933-949

Knowledge of Himalayan cryosphere seems to be an outstanding requirement for assessment of glacier storage, water balance analysis, planning of water resources and flood hazard monitoring. A stepwise approach through mapping glaciers and glacial lakes using satellite remote sensing data and investigating potential glacial lake outburst flood (GLOF) hazards was adopted for the three Hindukush, Karakoram and Himalayan (HKH) ranges of Pakistan. The findings of the study revealed 5,218 glaciers in the cryosphere of HKH ranges. The cumulative glacial cover of over 15,000 km² contains ice reserves of about 2,738 km³. About 46 % of the Karakoram glaciers are contributing 77 % to the total glacial cover and 87 % to the cumulative ice reserves of the country. The 33 % Himalayan glaciers and 21 % Hindukush glaciers contribute only 3 and 10 % ice reserves, respectively. Among 2,420 glacial lakes identified in the three HKH ranges, 52 were classified as critical lakes that can pose GLOF hazard for the downstream communities. Most of the potential hazardous lakes lie in the Karakoram and Himalayan ranges, the monitoring of which is crucial to reduce high risk of future floods hazard in this fragile mountain ecosystem of the Himalayan region.  相似文献   

Determinants of farmers’ choice of coping and adaptation measures to the drought hazard in northwest Balochistan,Pakistan   总被引：2，自引：0，他引：2  

Muhammad Ashraf  Jayant K. Routray  Muhammad Saeed 《Natural Hazards》2014,73(3):1451-1473

This study identifies the coping and adaptation behavior of the farm households and also examines the factors that influence farmers’ choice for drought-induced adaptation strategies. The study employs a multivariate probit model on 215 farm households’ survey data from northwest Balochistan, Pakistan. The findings reveal that the farmers have shown considerable fortitude in coping with the impacts of drought on their agro-based practices and employed several adaptation initiatives both at on-farm and off-farm levels. These include crop management, water management, adjustment in agricultural inputs, income diversification, economization of expenditure and consumption smoothing, migrating to other places to seek alternative sources of income, assets depletion, and borrowing. Empirically, it is depicted that landholding, annual income, livestock ownership, credit access, farmer-to-farmer extension, GOs/NGOs support increase the probability of farmers’ decision to cope and adapt better with drought hazard. This study implies for specific policy and practice-oriented solutions in order to cope with and adapt in drought situation.  相似文献   

Infinitesimal Orbits Around the Libration Points in the Elliptic Restricted Three Body Problem     

Ashraf Hamdy  Mostafa K. Ahmed  Mohamad Radwan  Fawzy Ahmed Abd El-Salam 《Earth, Moon, and Planets》2003,93(4):261-273

The objective of the present work is to develope explicit analytical expressions for the small amplitude orbits of the infinitesimal mass about the equilibrium points in the elliptic restricted three body problem. To handle this dynamical problem, the Hamiltonian for the elliptic problem is formed with the true anomaly and then with the eccentric anomaly as independent variables. The origin is then transformed to a fixed point and the Hamiltonian is developed up to O(4) in the eccentricity, e, (which plays the role of the small parameter of the problem) of the primaries. The integration of the model problem under consideration is undertaken by means of a perturbation technique based on Lie series developments, which leads to the solution of the canonical equations of motion.  相似文献   

Palaeoenvironmental Evolution During the Holocene in Itapeva Lake, RS, Brazil:Palynological and Geochemical Records     

Meyer K.E.B  Reichnart K  Marques T.M  Ashraf A.R  Mosbrugger V 《世界地质(英文版)》2002,5(2)

Based on palynological and geochemical data (Organic Carbon-Corg and Sulphur-S) of sedimentary samples from a vibrocore, considerations about the palaeoenvironmental evolution of Itapeva Lake region during the Holocene are made. The analysed core (BOXVI) consists in its lowermost part of a fine to medium sand packet, rich in glauconitic minerals, whose upper limit is considered to be the Holocene-Pleistocene contact. Using Cluster analysis on palynomorphs combined with Corg and S data, it was possible to distinguish four zones related to the Holocene transgression-regression cycle. Variations in Corg and S data permitted the recognition of changes in palaeosalinity. Zone 1 represents the beginning of the Holocene sedimentation; palynomorphs composition reveals a marsh environment under predominating freshwater conditions. In Zone 2, the occurrence of dinoflagellate cysts and high S values, indicating brackish water, reflects Holocene sea level highstand around 5100yrs. B.P. High concentration of Cyperaceae associated with a significant increase in Corg in Zone 3 indicates a typical marsh environment influenced at least sometimes by higher saline water, reflecting a regression phase. Salvinia natans (L)All. and Cyperaceae grains are considered to be the most significant palynomorpha in Zone 4, characterising a freshwater marsh. Based on the occurrence of dinoflagellates sample 2, Operculodinium sp., related to marine to estuarine environments, a question arises regarding about the time at which Barrier Ⅳ became completely closed.  相似文献   

Alternative climate data sources for distributed hydrological modelling on a daily time step   总被引：1，自引：0，他引：1  

Ashraf El‐Sadek  Max Bleiweiss  Manoj Shukla  Steve Guldan  Alexander Fernald 《水文研究》2011,25(10):1542-1557

Two major criteria in choosing climate data for use in hydrological modelling are the period of record of the data set and the proximity of the collection platform(s) to the basin under study. Conventional data sets are derived from weather stations; however, in many cases there are no weather stations sufficiently close to a basin to be representative of climate conditions in that basin. In addition, it is often the case either that the period of record for the weather station(s) does not cover the period of the proposed simulation or that there are gaps in the data. Therefore, the objectives of this study are to investigate alternative climate data sources for use in hydrological modelling and to develop a protocol for creating hydrological data sets that are spatially and temporally harmonized. The methods we used for constructing daily, spatially distributed, climatic data sets of precipitation, maximum and minimum temperature, wind speed, solar radiation, potential evapotranspiration, and relative humidity are described. The model used in this study was the Soil and Water Assessment Tool implemented on the Mimbres River Basin located in southwestern New Mexico, USA, for the period 2003–2006. Our hydrological simulations showed that two events in January and February 2005 were missed, while an event in August 2006 was well simulated. We have also investigated the usefulness of several other precipitation data sets and compared the simulation results. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Nonlinear propagation of dust-acoustic waves in a magnetized nonextensive dusty plasma     

S. Ashraf  S. Yasmin  M. Asaduzzaman  A. A. Mamun 《Astrophysics and Space Science》2013,348(2):495-500

A theoretical investigation has been made of obliquely propagating dust-acoustic solitary waves in a magnetized three-component dusty plasma, which consists of a negatively charged dust fluid, ions, and nonextensive electrons. The reductive perturbation method has been employed to derive the Korteweg-de Vries equation which admits a solitary wave solution. It has been shown that the combined effects of external magnetic field (obliqueness), ions, and electron nonextensivity change the behavior of these electrostatic solitary structures that have been found to exist with positive and negative potential in this dusty plasma model. The implications of our results in astrophysical and cosmological scenarios like vicinity of the Moon, magnetospheres of Jupiter and Saturn, dark-matter halos, hadronic matter, quark-gluon plasma, protoneutron stars, stellar polytropes etc. have been mentioned.  相似文献   

In Situ Time Series Estimation of Downwelling Diffuse Attenuation Coefficient at Southern Bay of Bengal     

P. Muhamed Ashraf  S. S. Shaju  D. Gayatri  P. Minu  B. Meenakumari 《Journal of the Indian Society of Remote Sensing》2013,41(3):725-730

The present study is aimed to determine the bio-optical characteristics of oceanic waters during South west monsoon in Bay of Bengal using hyperspectral radiometer. The variability of diffuse attenuation coefficient, K_d(λ), with chlorophyll a showed a good relation at shorter wavelengths, indicating the effect of phytoplankton on K_d(λ). The determination coefficient, R² at 412, 443, 490 and 555 nm were greater than 0.931. A good linear relation between K_d(490) and K_d(λ) was observed at shorter wavelengths. These relationships of K_d(λ) provides a platform to study the underwater light field during Southwest monsoon in Bay of Bengal.  相似文献   

Reliability assessment of water structures subject to data scarcity using the SCS-CN model     

Ayman G. Awadallah  Haitham Saad  Ashraf Elmoustafa  Ahmed Hassan 《水文科学杂志》2013,58(4):696-710

ABSTRACT

When discharge measurements are not available, design of water structures relies on using frequency analysis of rainfall data and applying a rainfall–runoff model to estimate a hydrograph. The Soil Conservation Service (SCS) method estimates the design hydrograph first through a rainfall–runoff transformation and next by propagating runoff to the basin outlet via the SCS unit hydrograph (UH) method. The method uses two parameters, the Curve Number (CN) and the time of concentration (T_c). However, in data-scarce areas, the calibration of CN and T_c from nearby gauged watersheds is limited and subject to high uncertainties. Therefore, the inherent uncertainty/variability of the SCS parameters may have considerable ramifications on the safety of design. In this research, a reliability approach is used to evaluate the impact of incorporating the uncertainty of CN and T_c in flood design. The sensitivity of the probabilistic outcome against the uncertainty of input parameters is calculated using the First Order Reliability Method (FORM). The results of FORM are compared with the conventional SCS results, taking solely the uncertainty of the rainfall event. The relative importance of the uncertainty of the SCS parameters is also estimated. It is found that the conventional approach, used by many practitioners, might grossly underestimate the risk of failure of water structures, due to neglecting the probabilistic nature of the SCS parameters and especially the Curve Number. The most predominant factors against which the SCS-CN method is highly uncertain are when the average rainfall value is low (less than 20 mm) or its coefficient of variation is not significant (less than 0.5), i.e. when the resulting rainfall at the design return period is low. A case study is presented for Egypt using rainfall data and CN values driven from satellite information, to determine the regions of acceptance of the SCS-CN method.