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81.
Simulating sensitivity of soil moisture and evapotranspiration under heterogeneous soils and land uses 总被引:9,自引:0,他引:9
Soil moisture (SM) plays an important role in land surface and atmospheric interactions. It modifies energy balance at the surface and the rate of water cycling between the land and atmosphere. In this paper we provide a sensitivity assessment of SM and ET for heterogeneous soil physical properties and for three land uses including irrigated maize, rainfed maize, and grass at a climatological time-scale by using a water balance model. Not surprisingly, the study finds increased soil water content in the root zone throughout the year under irrigated farming. Soil water depletes to its lowest level under rainfed maize cultivation. We find a ‘land use’ effect as high as 36 percent of annual total evapotranspiration, under irrigated maize compared to rainfed maize and grass, respectively. Sensitivity analyses consisting of comparative simulations using the model show that soil characteristics, like water holding capacity, influence SM in the root zone and affect seasonal total ET estimates at the climatological time-scale. This ‘soils’ effect is smaller than the ‘land use’ effect associated with irrigation but, it is a source of consistent bias for both SM and ET estimates. The ‘climate’ effect basically masks the ‘soils’ effect under wet conditions. These results lead us to conclude that appropriate representation of land use, soils, and climate are necessary to accurately represent the water and energy balance in real landscapes. 相似文献
82.
Projecting South Asian summer precipitation in CMIP3 models: A comparison of the simulations with and without black carbon 下载免费PDF全文
Considering the importance of black carbon (BC), this study began by comparing the 20th century simulation of South Asian summer climate in IPCC CMIP3, based on the scenario of models with and without BC. Generally, the multi-model mean of the models that include BC reproduced the observed climate relatively better than those that did not. Then, the 21st century South Asian summer precipitation was projected based on the IPCC CMIP3 projection simulations. The projected precipitation in the present approach exhibited a considerable difference from the multimodel ensemble mean (MME) of IPCC AR4 projection simulations, and also from the MME of the models that ignore the effect of BC. In particular, the present projection exhibited a dry anomaly over the central Indian Peninsula, sandwiched between wet conditions on the southern and northern sides of Pakistan and India, rather than homogeneous wet conditions as seen in the MME of IPCC AR4. Thus, the spatial pattern of South Asian summer rainfall in the future may be more complicated than previously thought. 相似文献
83.
Mureed Hussain Nisar Ahmed Wang Yan Chun Perveiz Khalid Azhar Mahmood Sajid Rashid Ahmad Umair Rasool 《Journal of the Geological Society of India》2017,89(3):331-338
The lower Indus basin is one of the largest hydrocarbon producing sedimentary basins in Pakistan. It is characterized by the presence of many hydrocarbon-bearing fields including clastic and carbonates proven reservoirs from the Cretaceous to the Eocene age. This study has been carried out in the Sanghar oil field to evaluate the hydrocarbon prospects of basal sand zone of lower Goru Formation of Cretaceous by using complete suite of geophysical logs of different wells. The analytical formation evaluation by using petrophysical studies and neutron-density crossplots unveils that litho-facies mainly comprising of sandstone. The hydrocarbons potentialities of the formation zone have been characterized through various isoparameteric maps such as gross reservoir and net pay thickness, net-to-gross ratio, total and effective porosity, shaliness, and water and hydrocarbons saturation. The evaluated petrophysical studies show that the reservoir has net pay zone of thickness range 5 to 10 m, net-togross ratio range of 0.17 to 0.75, effective porosity range of 07 to 12 %, shaliness range of 27 to 40 % and hydrocarbon saturation range of 12 to 31 %. However, in the net pay zone hydrocarbon saturation reaches up to 95%. The isoparametric charts of petrophysically derived parameters reveal the aerial distribution of hydrocarbons accumulation in basal sand unit of the lower Goru Formation which may be helpful for further exploration. 相似文献
84.
85.
Mohammad Reza Mansouri Daneshvar Mahmood Khosravi Taghi Tavousi 《Natural Hazards》2014,74(3):1539-1553
Several studies have reported the increased values of surface-latent heat flux (SLHF) and rainfall events prior to the earthquakes as the seismic precursors. In order to investigate the variation of two mentioned atmospheric variables, we analyzed 39 major earthquakes in the Middle East based on the time series of NASA remote sensing data. On this basis, we observed that accumulated rainfall and SLHF of about 29 earthquakes were higher than 10 mm and 50 W/m2, respectively (~75 %), over 3–23 days prior to the main shock of major earthquakes. We believed that the records of atmospheric variables are the consequence of a seismic-triggered chain including of air ionization, surface-latent heat exhalation, water vapor condensation and subordinate rainfall as the atmospheric responses to lithospheric motions. This seismic triggering in the Middle East has averagely caused to accumulated rainfall of ~35 mm and maximum SLHF of ~115 W/m2 over the 3–23 days prior to 39 major earthquakes. To investigate of spatial correlation between earthquakes and atmospheric variations, we clustered 39 major earthquakes in eight seismological regions. Then, we estimated the moderate and strong correlation (R 2) between preceding times of earthquakes with magnitude of major earthquakes and their hypocenter depth equal to 0.48 and 0.68, respectively. 相似文献
86.
S. Shaheen Q. Mahmood A. Pervez N. Mirza Z. A. Bhatti T. Hayat S. S. Meryem F. Ullah 《International Journal of Environmental Science and Technology》2016,13(6):1581-1590
The role of rhizospheric microbes of giant reed (Arundo donax L.) in Cr uptake from hydroponic culture was investigated. The control group was exposed to Cr in range of 25–100 mg L?1 containing a control itself (with no metal addition). The experimental group received same Cr treatments, but in addition was exposed to antibiotic treatment in order to inhibit rhizospheric bacteria. The range of Cr accumulated in the roots was 3–7.65 mg L?1; in stem it ranged 2.15–42.4 mg kg?1; while in leaves, the range of Cr content was 13.7–15 mg kg?1. Overall, Cr uptake in A. donax (without rhizobacterial inhibition) was root < leaf < stem. However, the amount of Cr uptake in plants with rhizobacterial inhibition was significantly less (~4.6-folds in 100 mg L?1 Cr treatment) than those without such inhibition clearly highlighting that rhizobacterial inhibition decreased the Cr uptake. The experimental results clearly demonstrated that the inhibition of the rhizobacterial populations had great influence on the Cr uptake. However, Cr uptake could not be completely inhibited as some metal uptake was observed after the rhizobacterial inhibition although it was significantly less than the Cr uptake of plants without such inhibition. 相似文献
87.
Khawar Ashfaq AHMED Sarfraz KHAN Mahmood SULTAN UMAIR Bin Nisar Kalim ULLAH Al -Hseinat MU’AYYAD 《《地质学报》英文版》2019,93(6):1711-1720
The precise seismic substructural interpretation of the Turkwal oil field in the Central Potwar region of district Chakwal of Pakistan has been carried out. The research work was confined to the large fore-thrust that serves as an anticlinal structural trap through ten 2D seismic lines. A precise seismic substructural model of the Eocene Chorgali Limestone with precise orientation of thrust and oblique slip faults shows the presence of a huge fracture, which made this deposit a good reservoir. The abrupt surface changes in dip azimuth for the Eocene Chorgali Limestone verifies the structural trends and also the presence of structural traps in the Turkwal field. The logs of three wells (Turkwal deep X-2, Turkwal-01 and Fimkassar-01) were analyzed for petrophysical studies, well synthetic results and generation of an Amplitude Versus Offset (AVO) model for the area. The AVO model of Turkwal deep X-2 shows abrupt changes in amplitude, which depicts the presence of hydrocarbon content. Well correlation technique was used to define the overall stratigraphic setting and the thickness of the reservoir formation in two wells, Turkwal-01 and Turkwal deep X-2. The Eocene Chorgali Limestone in Turkwal-01 is an upward thrusted anticlinal structure and because of the close position of both wells to the faulted anticlinal structure, its lesser thickness differs compared to Turkwal deep X-2. The overall results confirm that the Turkwal field is comparable to several similar thrust-bound oil-bearing structures in the Potwar basin. 相似文献
88.
Natural Hazards - Pakistan is exposed to hydro-meteorological and geological hazards. Flood is one of the hydro-meteorological hazards, and so far 25 major floods have occurred in Indus River... 相似文献
89.
90.
Extinction depth and evapotranspiration from ground water under selected land covers 总被引:7,自引:0,他引:7
In many landscapes, vegetation extracts water from both the unsaturated and the saturated zones. The partitioning of evapotranspiration (ET) into vadose zone evapotranspiration and ground water evapotranspiration (GWET) is complex because it depends on land cover and subsurface characteristics. Traditionally, the GWET fraction is assumed to decay with increasing depth to the water table (DTWT), attaining a value of 0 at what is termed the extinction depth. A simple assumption of linear decay with depth is often used but has never been rigorously examined using unsaturated-saturated flow simulations. Furthermore, it is not well understood how to relate extinction depths to characteristics of land cover and soil texture. In this work, variable saturation flow theory is used to simulate GWET for three land covers and a range of soil properties under drying soil conditions. For a water table within half a meter of the land surface, nearly all ET is extracted from ground water due to the close hydraulic connection between the unsaturated and the saturated zones. For deep-rooted vegetation, the decoupling of ground water and vadose zone was found to begin at water table depths between 30 and 100 cm, depending on the soil texture. The decline of ET with DTWT is better simulated by an exponential decay function than the commonly used linear decay. A comparison with field data is consistent with the findings of this study. Tables are provided to vary the extinction depth for heterogeneous landscapes with different vegetation cover and soil properties. 相似文献