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91.
Muhammad Mubashar Dogar Fred Kucharski Syed Azharuddin 《Journal of Earth System Science》2017,126(2):30
ENSO is considered as a strong atmospheric teleconnection that has pronounced global and regional circulation effects. It modifies global monsoon system, especially, Asian and African monsoons. Previous studies suggest that both the frequency and magnitude of ENSO events have increased over the last few decades resulting in a need to study climatic impacts of ENSO magnitude both at global and regional scales. Hence, to better understand the impact of ENSO amplitude over the tropical and extratropical regions focussing on the Asian and African domains, ENSO sensitivity experiments are conducted using ICTPAGCM (‘SPEEDY’). It is anticipated that the tropical Pacific SST forcing will be enough to produce ENSO-induced teleconnection patterns; therefore, the model is forced using NINO3.4 regressed SST anomalies over the tropical Pacific only. SPEEDY reproduces the impact of ENSO over the Pacific, North and South America and African regions very well. However, it underestimates ENSO teleconnection patterns and associated changes over South Asia, particularly in the Indian region, which suggests that the tropical Pacific SST forcing is not sufficient to represent ENSO-induced teleconnection patterns over South Asia. Therefore, SST forcing over the tropical Indian Ocean together with air–sea coupling is also required for better representation of ENSO-induced changes in these regions. Moreover, results obtained by this pacemaker experiment show that ENSO impacts are relatively stronger over the Inter-Tropical Convergence Zone (ITCZ) compared to extratropics and high latitude regions. The positive phase of ENSO causes weakening in rainfall activity over African tropical rain belt, parts of South and Southeast Asia, whereas, the La Niña phase produces more rain over these regions during the summer season. Model results further reveal that ENSO magnitude has a stronger impact over African Sahel and South Asia, especially over the Indian region because of its significant impact over the tropical Atlantic and the Indian Ocean through Walker circulation. ENSO-induced negative (positive) NAO-like response and associated changes over Southern Europe and North Africa get significantly strong following increased intensity of El Niño (La Niña) in the northern (southern) hemisphere in the boreal winter (summer) season. We further find that ENSO magnitude significantly impacts Hadley and Walker circulations. The positive phase of ENSO (El Niño) overall strengthens Hadley cell and a reverse is true for the La Niña phase. ENSO-induced strengthening and weakening of Hadley cell induces significant impact over South Asian and African ITCZ convective regions through modification of ITCZ/monsoon circulation system. 相似文献
92.
Syed Muhammad Zubair Younis Muhammad Majid Ahmad Ammar 《Arabian Journal of Geosciences》2017,10(18):404
The impacts of floods and droughts are intensified by climate change, lack of preparedness, and coordination. The average rainfall in study area is ranging from 200 to 400 mm per year. Rain gauge generally provides very accurate measurement of point rain rates and the amounts of rainfall but due to scarcity of the gauge locations provides very general information of the area on regional scale. Recognizing these practical limitations, it is essential to use remote sensing techniques for measuring the quantity of rainfall in the Middle Indus. In this research, Tropical Rainfall Measuring Mission (TRMM) estimation can be used as a proxy for the magnitude of rainfall estimates from classical methods (rain gauge), quantity, and its spatial distribution for Middle Indus river basin. In order to use TRMM satellite data for discharge measurement, its accuracy is determined by statistically comparing it with in situ gauged data on daily and monthly bases. The daily R 2 value (0.42) is significantly lower than monthly R 2 value (0.82), probably due to the time of summation of TRMM 3-hourly precipitation data into daily estimates. Daily TRMM data from 2003 to 2012 was used as input forcing in Soil and Water Assessment Tool (SWAT) hydrological model along with other input parameters. The calibration and validation results of SWAT model give R 2 = 0.72 and 0.73 and Nash-Sutcliffe coefficient of efficiency = 0.69 and 0.65, respectively. Daily and monthly comparison graphs are generated on the basis of model discharge output and observed data. 相似文献
93.
Fluvial depositional systems constitute diverse host for the hydrocarbons all over the globe. Nevertheless, predicting the hydrocarbon sands within these assorted sand systems is a challenge for the prospect generation. We apply the continuous wavelet transform of spectral decomposition technique to a 3D seismic data of the Miano Gas Field in the Indus Platform, Pakistan. Full spectrum seismic attributes like the amplitude and root mean square (RMS) detect the reservoir sands down to a restricted reservoir compartment. Nonetheless, the continuous wavelet transforms can be advantageous in imaging and enactment of these clastic reservoirs within the whole reservoir zone. Rock physics reveal high-quality reservoir with an average porosity ~25% together with the discrimination of lithology/fluids, signifying the bright chances for ascertaining the potential stratigraphic reservoirs. 相似文献
94.
Mohsin Muhammad Mu Yongtong Memon Aamir Mahmood Kalhoro Muhammad Talib Shah Syed Baber Hussain 《中国海洋湖沼学报》2017,35(4):936-946
Pakistani marine waters are under an open access regime.Due to poor management and policy implications,blind fishing is continued which may result in ecological as well as economic losses.Thus,it is of utmost importance to estimate fishery resources before harvesting.In this study,catch and effort data,1996-2009,of Kiddi shrimp Parapenaeopsis stylifera fishery from Pakistani marine waters was analyzed by using specialized fishery software in order to know fishery stock status of this commercially important shrimp.Maximum,minimum and average capture production of P.stylifera was observed as 15 912 metric tons(mt)(1997),9 438 mt(2009) and 11 667 mt/a.Two stock assessment tools viz.CEDA(catch and effort data analysis) and ASPIC(a stock production model incorporating covariates) were used to compute MSY(maximum sustainable yield) of this organism.In CEDA,three surplus production models,Fox,Schaefer and Pella-Tomlinson,along with three error assumptions,log,log normal and gamma,were used.For initial proportion(IP) 0.8,the Fox model computed MSY as 6 858 mt(CV=0.204,R~2=0.709) and 7 384 mt(CV=0.149,R~2=0.72) for log and log normal error assumption respectively.Here,gamma error produced minimization failure.Estimated MSY by using Schaefer and Pella-Tomlinson models remained the same for log,log normal and gamma error assumptions i.e.7 083 mt,8 209 mt and 7 242 mt correspondingly.The Schafer results showed highest goodness of fit R~2(0.712) values.ASPIC computed MSY,CV,R~2,F_(MSY)and B_(MSY) parameters for the Fox model as 7 219 mt,0.142,0.872,0.111 and 65 280,while for the Logistic model the computed values remained 7 720 mt,0.148,0.868,0.107 and 72 110 correspondingly.Results obtained have shown that P.stylifera has been overexploited.Immediate steps are needed to conserve this fishery resource for the future and research on other species of commercial importance is urgently needed. 相似文献
95.
The variation of potential gradient in mist, haze, and fog has been studied. During the formation of these hydrometers the
potential gradients were found to increase. Large positive potential gradients were observed during dense fog conditions.
Possible charge generation mechanisms responsible for these potential gradients during fog formation are discussed. 相似文献
96.
97.
Rambabu Singh A. S. Venkatesh Tajdarul H. Syed L. Surinaidu Srinivas Pasupuleti S. P. Rai Manoj Kumar 《Environmental Earth Sciences》2018,77(15):548
The present study explores the use of stable isotopes and major ion chemistry of various water sources such as mine water, groundwater, river water, and rainwater to identify the dominant hydrogeochemical process that controls the water quality in the active opencast coal mining area of the Korba Coalfield, India. Different hydrochemical models have revealed that the study area is mostly characterized by two facies alongside a dominance by ion exchange: i.e., a slightly mineralized Ca2+–Mg2+–Cl? and a meteorically derived Ca2+–HCO3? fresh water facies. In the isotope bivariate plot, the samples plot to the right of the LMWL and slopes observed in pre (4.94) and post-monsoon (5.85) seasons are not as steep as the LMWL (7.95) and this warrants the suggestion that meteoric water is the major source that replenishes the dynamic groundwater resource in the study area after being subjected to evaporation. The negative d-excess values (<?0) and enrichment of the δ18O ratio observed at some locations suggests a non-equilibrium process and a “mechanism of mixing”. A noteworthy fact is that isotopically river water is in tandem with the mine water samples for both seasons and testifies to a hydraulic connectivity between Hasdeo River water and mine water through a major fault. It is substantiated by mine inflows assessed by the sump test for Kusmunda and Gevra, which is two times higher than the predicted values by Darcy’s law. The wide variation in the isotopic composition is attributed to different vapor sources viz., southwest monsoon (SW) that originates in the Arabian Sea and locally driven air moisture from surface water bodies. 相似文献
98.
Groundwater is a valuable natural resource for drinking, domestic, livestock use, and irrigation, especially in arid and semi-arid regions like the Garmiyan belt in Kurdistan region. The Awaspi watershed is located 50 km east of Kirkuk city, south Kurdistan, Iraq; and covers an area of 2146 km2. The paper presents result of a study aimed at: (1) mapping and preparing thematic layers of factors that control groundwater recharge areas, and (2) determination of sites suitable for groundwater recharge. We used available data such as geological map, groundwater depth map, digital elevation model (DEM), Landsat 8 imagery, and tropical rainfall measuring mission (TRMM) data for this study. These data, supplemented by slope features, lithology, land use land cover, rainfall, groundwater depth, drainage density, landform, lineament density, elevation and topographic position index, were utilized to create thematic maps to identify suitable areas of groundwater recharge, using GIS and remote sensing techniques. Analytic hierarchy process (AHP) was applied to weight, rank, and reclassify these maps in the ArcGIS 10.3 environment, to determine the suitable sites for groundwater recharge within the Awaspi watershed. Fifty-five percent of the total area of the watershed was found to be suitable for groundwater recharge; whereas 45% of the area was determined to have poor suitability for groundwater recharge, but can be used for surface water harvesting. 相似文献
99.
Incised-valley shale systems are renowned as the fruitful exploration domains. However, the stratigraphic heterogeneity is significant, and thus, identifying the porous compartments within the thin-bedded and fractured shale system is one of the unconventional stratigraphic challenges. We present an innovative scheme for the exploration of the porous unconventional resources within the south Indus basin, Pakistan. The continuous wavelet transforms (CWT) exclusively detects the porous shales within the complete fractured system as compared to the full spectrum seismic data interpretation tool. The seismic amplitude, instantaneous frequency, and reflection strength tools show some tuning effects due to lithology and fluids. However, the tuning block of 28 Hz envelope sub-bands in conjunction with instantaneous phase tool accurately mark out the shale-plugged pinch out reservoirs. The synthetic wedge model based on the conventional seismic wavelet resolves the shale bed (incised-valley shale-filled lens) of about 23 m thickness, but shows limited imaging capability due to frequency band limitation for the porous shale locale. The acoustic impedance based on instantaneous spectral porosity modeling using the tuning volume of 28 Hz CWT has spectacularly resolved the thin-beds (gas shows) within the porosity range of 20 to 30%, which may have implications for future exploration of unconventional stratigraphic plays. 相似文献
100.
HAN Jibin XU Jianxin Syed Asim HUSSAIN JIANG Hongchen MA Yunqi XU Kai MA Haizhou 《《地质学报》英文版》2021,95(2):531-540
The Gas Hure Salt Lake(GHSL) in the northwestern Qaidam Basin, western China, is rich in boron(B)resources, but its B-resource origin is hardly known. Hydrochemical compositions and B isotope characteristics of different waters were collected around the GHSL, including the river water, stream water, spring water, salt-lake brine,intercrystalline brine, well water, drilling brine, and solar pond brine. The hydrochemical signatures suggest that silicates,carbonates and evaporates are the main B-bearing rocks during the water dynamic. The reservoir estimation of B resources shows that the Kulamulekesay River(KLMR) and the Atekan River(ATKR) contribute annually 18.3 tons and 22.84 tons of B, respectively, with a total amount of 11.72 × 10~4 tons of B during the past 5.7 ka. In comparison with the known B reservoir(32.96 × 10~4 tons) in the GHSL, a significant amount of B in the GHSL was probably recharged from deep fluids and sediments around the GHSL. The B concentration and B-enrichment degree are shaped by the evaporation process,which are highly elevated at the carnallite and bischofite stages. 相似文献