Polar caps on active stars: magnetic flux emergence and transport     

D. H. Mackay  M. Jardine  A. Collier Cameron  J.-F. Donati  G. A. J. Hussain 《Monthly notices of the Royal Astronomical Society》2004,354(3):737-752

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Uncertainty analysis of runoff and sedimentation in a forested watershed using sequential uncertainty fitting method     

Tanveer Abbas  Ghulam Nabi  Muhammad W. Boot  Fiaz Hussain  Muhammad I. Azam  HuiJun Jin  Muhammad Faisal 《寒旱区科学》2016,8(4):297-310

The Soil and Water Assessment Tool(SWAT) was implemented in a small forested watershed of the Soan River Basin in northern Pakistan through application of the sequential uncertainty fitting(SUFI-2) method to investigate the associated uncertainty in runoff and sediment load estimation. The model was calibrated for a 10-year period(1991–2000) with an initial 4-year warm-up period(1987–1990), and was validated for the subsequent 10-year period(2001–2010). The model evaluation indices R~2(the coefficient of determination), NS(the Nash-Sutcliffe efficiency), and PBIAS(percent bias) for stream flows simulation indicated that there was a good agreement between the measured and simulated flows. To assess the uncertainty in the model outputs, p-factor(a 95% prediction uncertainty, 95PPU) and r-factors(average wideness width of the 95 PPU band divided by the standard deviation of the observed values) were taken into account. The 95 PPU band bracketed 72% of the observed data during the calibration and 67% during the validation. The r-factor was 0.81 during the calibration and 0.68 during the validation. For monthly sediment yield, the model evaluation coefficients(R~2 and NS) for the calibration were computed as 0.81 and 0.79, respectively; for validation, they were 0.78 and 0.74, respectively. Meanwhile, the 95 PPU covered more than 60% of the observed sediment data during calibration and validation. Moreover, improved model prediction and parameter estimation were observed with the increased number of iterations. However, the model performance became worse after the fourth iterations due to an unreasonable parameter estimation. Overall results indicated the applicability of the SWAT model with moderate levels of uncertainty during the calibration and high levels during the validation. Thus, this calibrated SWAT model can be used for assessment of water balance components, climate change studies, and land use management practices.  相似文献   

A case study of Precambrian to Eocene sediments’ hydrocarbon potential assessment in Central Indus Basin of Pakistan     

Shazia Asim  Peimin Zhu  Shahid Nadeem Qureshi  Muhammad Tayyab Naseer 《Arabian Journal of Geosciences》2015,8(12):10339-10357

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应用CEDA和ASPIC软件包对巴基斯坦国的多齿蛇鲻(Saurida tumbil)渔业的最大持续产量的初步研究     

KALHORO Muhsan Ali  LIU Qun  MEMON Khadim Hussain  WARYANI Baradi  SOOMRO Shamsher Hyder 《海洋学报(英文版)》2015,34(2):68-73

The catch and effort data analysis(CEDA) and ASPIC(a stock assessment production model incorporating covariates) computer software packages were used to estimate the maximum sustainable yield(MSY) from the catch and effort data of Greater lizardfish Saurida tumbil fishery of Pakistan from 1986 to 2009. In CEDA three surplus production models of Fox, Schaefer and Pella-Tomlinson were used. Here initial proportion(IP) of 0.5 was used because the starting catch was roughly 50% of the maximum catch. With IP = 0.5, the estimated MSY from Fox model were 20.59 mt and 38.16 mt for normal and log-normal error assumptions, while the MSY from Schaefer and Pella-Tomlinson were 60.40, 60.40 and 60.40 mt, for normal, log-normal and gamma error assumptions respectively. The MSY values from Schaefer and Pella-Tomlinson models of three error assumptions were the same. The R2 values from those three models were above 0.6. When IP = 0.5, the MSY values estimated from ASPIC from Fox were 132 mt, and from logistic model were 69.4 mt, with R2 value above 0.8. Therefore we suggest the MSY of S. tumbil fishery from Pakistan to be 60–70 mt, which is higher than the latest catch, thus we would recommend that the fishing efforts for this fishery may be kept at the current level.  相似文献   

Multi-topographical landscape: comparative vulnerability of climate-induced disaster-prone rural area of Pakistan     

Memon  Manzoor Hussain  Ahmed  Rafiq 《Natural Hazards》2022,111(2):1575-1602

Pakistan, being an agro-based economy, is considered most vulnerable to the impacts of climate change. The country is susceptible to many natural catastrophes and climate-induced events due to intra-geographical and intra-topographical disparities. This paper is an attempt to measure the relative vulnerability of diverse topographies in rural areas of Pakistan using vulnerability and capacity index tool. The results are based on the findings of primary survey data (350 households from 17 rural communities). Accordingly, and as expected, the key relative differences are attributed to topographical conditions besides the basic quandary of rural areas of Pakistan. The topographical attributes are largely linked to the nature of hazards and relative impacts. While the other aspects of vulnerability in all topographies stem out of inappropriate infrastructure, low education, and institutional factors. The absence of multi-sectoral and productive economic opportunities also poses an adverse impact on the resilience of households in rural areas. The women and households headed by females are found relatively more vulnerable than male-headed households.

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腾格里沙漠盐湖氯同位素地球化学特征     

韩凤清  毛庆飞  马茹莹  张燕霞  孙宇强  韩继龙  年秀清  刘文玉  SYED Asim Hussain  马喆 《湖泊科学》2018,30(4):1152-1160

δ~(37)Cl值可以用来指示盐湖演化过程中卤水的蒸发浓缩程度、可能的补给来源和控制因素,本文对腾格里沙漠地区12个代表性盐湖卤水样品开展了氯同位素组成研究.结果表明,研究区内沙漠盐湖卤水的δ~(37)Cl值变化范围为-0.10‰~1.36‰,平均值为0.55‰;其中,硫酸钠亚型卤水的δ~(37)Cl值范围为-0.10‰~1.36‰(平均值为0.56‰),硫酸镁亚型卤水的δ~(37)Cl值范围为0.14‰~0.82‰(平均值为0.48‰).对比柴达木盆地现代盐湖分析数据,发现区内沙漠盐湖的δ~(37)Cl平均值明显大于柴达木盆地盐湖的δ~(37)Cl平均值,并且,硫酸钠亚型卤水δ~(37)Cl最高,硫酸镁亚型卤水次之,氯化物型卤水最小.基于不同盐湖地下水咸化程度以及盐湖卤水中δ~(37)Cl值与Br/Cl系数关系的研究,揭示了研究区东部和东北部盐湖可能受到第三系地层咸水的补给,而其他盐湖主要受蒸发浓缩作用影响.δ~(37)Cl值分布特征则显示,腾格里沙漠地区部分盐湖在形成过程中可能受到区域构造活动诱发的第三系深部水补给及水-岩作用等多重因素的影响.  相似文献   

High-resolution X-ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure     

Arif Hussain  Peter D. W. Haughton  Patrick M. Shannon  Jonathan N. Turner  Colm S. Pierce  Arnau Obradors-Latre  Simon P. Barker  Ole J. Martinsen 《Sedimentology》2020,67(6):2850-2882

Hybrid event beds form when turbidity currents that transport or locally acquire significant quantities of mud decelerate. The mud dampens turbulence driving flow transformations, allowing both mud and sand to settle into dense, near-bed fluid layers and debris flows. Quantifying details of the mud distribution vertically in what are often complex tiered deposits is critical to reconstructing flow processes and explaining the diverse bed types left by mud-bearing gravity flows. High-resolution X-ray fluorescence core scanning provides continuous vertical compositional profiles that can help to constrain mud distribution at sub-millimetre scale, offering a significant improvement over discrete sampling. The approach is applied here to cores acquired from the Pennsylvanian Ross Sandstone Formation, western Ireland, where a range of hybrid event beds have been identified. Raw X-ray fluorescence counts are calibrated against element concentrations and mineral abundances determined on coincident core plugs, with element and element log-ratios used as proxies to track vertical changes in abundances of quartz, illite (including mica), chlorite and calcite cement. New insights include ‘stepped’ (to higher values) as opposed to ‘saw-tooth’ vertical changes in mud content and the presence of compositional banding that would otherwise be overlooked. Hybrid event beds in basin floor sheets that arrived ahead of the prograding fan system have significantly cleaner sandy components than those in mid-fan lobes. The latter may imply that the heads of the currents emerging from mid-fan channels entrained significant mud immediately before they collapsed. Many of the H3 debrites are bipartite with a sandier H3a division attributed to re-entrainment and mixing of a trailing debris or fluid mud flow (H3b) with sand left by the forward part of the flow. Hybrid event bed structure may thus partly reflect substrate interaction and mixing during deposition, and the texture of the bed divisions may not simply mirror those in the suspensions from which they formed.  相似文献   

Shrinking greenery: Land use and land cover changes in Kurram Agency,Kohi Safid Mountains of north-western Pakistan     

Kamal Hussain  Fazlul Haq  Fazlur Rahman 《山地科学学报》2018,15(2):296-306

Deforestation and other Land Use and Land Cover (LULC) changes, driven by variety of physical and anthropogenic factors, have altered the mountainous environment. Mountains around the world including northern and north western belts of Pakistan are highly sensitive to deforestation and other LULC changes, which have profound impacts on various sectors of bio-physical and socio-economic systems. Assessment of LULC changes has high significance for protection, conservation and monitoring mountainous environment. The present study is an attempt to assess the landscape changes with particular reference to forest cover depletion in Kurram Agency located in the north western mountain belt of Pakistan. For detailed comparative analysis the study area has been divided into three sections, which coincide with the present administrative divisions of the Agency, i.e., Upper, Lower and Central Kurram. Temporal span of this study covers four decades. In this study, land use map of 1970 and land sat satellite imageries of 1987, 2000 and 2014 were used as spatial data sets. The images were processed and classified into six LULC classes through geospatial packages and change detection maps were prepared for each division and time period. Findings of the study reveal two trends in the four major LULC categories. Forest and rangeland have shrunk, on average, by 15% and 7.5% respectively while, bare soil and rocks outcrops have expanded by 89% and agriculture land by 7.2% in Kurram agency. The water bodies and snow cover have minor fluctuation in its land area. Major causes of shrinking greenery is attributed to high influx of Afghan refugees and high energy demand of growing population. However, with outflow of the refugees from Kurram agency the general trend in forest cover has reverted and deforestation rate has slowed down.  相似文献   

Factors Influencing the Atmospheric Depositional Fluxes of Stable Pb, 210Pb, and 7Be into Chesapeake Bay   总被引：3，自引：0，他引：3  

Guebuem Kim  N. Hussain  J. R. Scudlark  T. M. Church 《Journal of Atmospheric Chemistry》2000,36(1):65-79

Atmospheric depositional fluxes of ⁷Be and²¹⁰Pb (bulk) and stable Pb (wet) were measuredsimultaneously for one year (from September 1995–August 1996) atStillpond, Maryland on the uppereastern shore of the Chesapeake Bay. The annual total(bulk) depositional fluxes of ²¹⁰Pb and ⁷Bewere 0.78 and 13 dpm cm^-2, respectively, andagree well with other previously reported results atnearby locations such as Norfolk, VA and Lewes, DE. The wet depositional flux of stable Pb (58 ng cm^-2 yr^-1)was also similar to thatmeasured at other Chesapeake sites during 1990–1991(55 ng cm^-2 yr^-1, for both Wye and Elms,Maryland). This suggests that a constant Pb flux hasbeen reached since the mandatory use of unleadedgasoline was instituted. The concentrations of⁷Be, ²¹⁰Pb, and to a lesser extent stable Pbwere diluted exponentially by precipitation, based onconcentrations versus precipitation plots. Due tohigher enrichment of ²¹⁰Pb in the lowertroposphere, the dilution effect was largest on²¹⁰Pb (i.e., controlled mainly by below-cloudscavenging processes), and thus its depositional fluxincrease is negligible as precipitation amountincreases. A good correlation between the amount ofprecipitation and total depositional flux of ⁷Beand stable Pb, which are more enriched in the uppertroposphere, suggests that precipitation amount isimportant in controlling their fluxes (i.e.,controlled by both below-cloud scavenging and in-cloudcondensation processes). Based on ⁷Be versus²¹⁰Pb plots, it appears that ⁷Be, relativeto ²¹⁰Pb, is less efficiently scavenged bysnowfall. Our results suggest that in addition toprecipitation amounts, marine air-mass transport orsnowfall may be important factors in controlling theseasonal variability of the fallout fluxes of tracemetals in coastal areas.  相似文献   

Disintegration of uncertainties associated with real-time multi-satellite precipitation products in diverse topographic and climatic area in Pakistan     

Muhammad MASOOD  Ghulam NABI  Muhammad BABUR  Aftab Hussain AZHAR  Muhammad KALEEM ULLAH 《山地科学学报》2021,(3):716-734

Satellite-based Precipitation Estimates(SPEs)have gained importance due to enhanced spatial and temporal resolution,particularly in Indus basin,where raingauge network has fewer observation stations and drainage area is laying in many countries.Formulation of SPEs is based on indirect mechanism,therefore,assessment and correction of associated uncertainties is required.In the present study,disintegration of uncertainties associated with four prominent real time SPEs,IMERG,TMPA,CMORPH and PERSIANN has been conducted at grid level,regional scale,and summarized in terms of regions as well as whole study area basis.The bias has been disintegrated into hit,missed,false biases,and Root Mean Square Error(RMSE)into systematic and random errors.A comparison among gauge-and satellite-based precipitation estimates at annual scale,showed promising result,encouraging use of real time SPEs in the study area.On grid basis,at daily scale,from box plots,the median values of total bias(-0.5 to 0.5 mm)of the used SPEs were also encouraging although some under/over estimations were noted in terms of hit bias(-0.15 to 0.05 mm/day).Relatively higher values of missed(0.3 to 0.5 mm/day)and false(0.5 to 0.7 mm/day)biases were observed.The detected average daily RMSE,systematic errors,and random errors were also comparatively higher.Regional-scale spatial distribution of uncertainties revealed lower values of uncertainties in plain areas,depicting the better performance of satellite-based products in these areas.However,in areas of high altitude(>4000 m),due to complex topography and climatic conditions(orographic precipitation and glaciated peaks)higher values of biases and errors were observed.Topographic barriers and point scale gauge data could also be a cause of poor performance of SPEs in these areas,where precipitation is more on ridges and less in valleys where gauge stations are usually located.Precipitation system’s size and intensity can also be a reason of higher biases,because Microwave Imager underestimate precipitation in small systems(<200 km²)and overestimate in large systems(>2000 km²).At present,use of bias correction techniques at daily time scale is compulsory to utilize real time SPEs in estimation of floods in the study area.Inter comparison of satellite products indicated that IMERG gave better results than the others with the lowest values of systematic errors,missed and false biases.  相似文献