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  • Articles  (74)
  • Geography  (74)
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  • Articles  (74)
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  • 1
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    An improved hindcast approach for evaluation and diagnosis of physical processes in global climate models (2015)
    Wiley
    Details
    Publication Date: 2015-10-20
    Description: We present an improved procedure of generating initial conditions (ICs) for climate model hindcast experiments with specified sea surface temperature and sea ice. The motivation is to minimize errors in the ICs and lead to a better evaluation of atmospheric parameterizations' performance in the hindcast mode. We apply state variables (horizontal velocities, temperature and specific humidity) from the operational analysis/reanalysis for the atmospheric initial states. Without a data assimilation system, we apply a two-step process to obtain other necessary variables to initialize both the atmospheric (e.g., aerosols and clouds) and land models (e.g., soil moisture). First, we nudge only the model horizontal velocities towards operational analysis/reanalysis values, given a 6-hour relaxation time scale, to obtain all necessary variables. Compared to the original strategy in which horizontal velocities, temperature and specific humidity are nudged, the revised approach produces a better representation of initial aerosols and cloud fields which are more consistent and closer to observations and model's preferred climatology. Second, we obtain land ICs from an offline land model simulation forced with observed precipitation, winds, and surface fluxes. This approach produces more realistic soil moisture in the land ICs. With this refined procedure, the simulated precipitation, clouds, radiation, and surface air temperature over land are improved in the Day 2 mean hindcasts. Following this procedure, we propose a “Core” integration suite which provides an easily repeatable test allowing model developers to rapidly assess the impacts of various parameterization changes on the fidelity of modelled cloud-associated processes relative to observations. This article is protected by copyright. All rights reserved.
    Electronic ISSN: 1942-2466
    Topics: Geography , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Ancient DNA identification of domestic animals used for leather objects in Central Asia during the Bronze Age (2016)
    Sage
    In: Holocene
    Details
    Publication Date: 2016-09-10
    Description: The arid climate of many regions within Central Asia often leads to excellent archaeological preservation, especially in sealed funerary contexts, allowing for ancient DNA analyses. While geneticists have looked at human remains, clothes, tools, and other burial objects are often neglected. In this paper, we present the results of an ancient DNA study on Bronze Age leather objects excavated from tombs of the Wupu cemetery in the Hami Oasis and Yanghai cemetery in the Turpan Oasis, both in Xinjiang Uyghur Autonomous Region of northwestern China. In addition to species identification of goat ( Capra aegagrus/hircus ), sheep ( Ovis orientalis/aries ), and cattle ( Bos primigenius/taurus ), mitochondrial haplogroups were determined for several samples. Our results show that Bronze Age domesticated goats and sheep from the Hami and Turpan oases possessed identical or closely related haplotypes to modern domestic animals of this area. The absence of leather produced from wild animals emphasizes the importance of animal husbandry in the cultures of Wupu and Yanghai.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 3
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    Spatiotemporal characteristics of precipitation and extreme events on the Loess Plateau of China between 1957 and 2009 (2013)
    Wiley
    Details
    Publication Date: 2013-06-25
    Description: Spatiotemporal trends in precipitation may influence vegetation restoration, and extreme precipitation events profoundly affect soil erosion processes on the Loess Plateau. Daily data collected at 89 meteorological stations in the area between 1957 and 2009 were used to analyze the spatiotemporal trends of precipitation on the Loess Plateau and the return periods of different types of precipitation events classified in the study. Nonparametric methods were employed for temporal analysis, and the Kriging interpolation method was employed for spatial analysis. The results indicate a small decrease in precipitation over the Loess Plateau in last 53 years (although a Mann–Kendall test did not show this decrease to be significant), a southward shift in precipitation isohyets, a slightly delayed rainy season, and prolonged return periods, especially for rainstorm and heavy rainstorm events. Regional responses to global climate change have varied greatly. A slightly increasing trend in precipitation in annual and sub-annual series, with no obvious shift of isohyets, and an evident decreasing trend in extreme precipitation events were detected in the northwest. In the southeast, correspondingly, a more seriously decreasing trend occurred, with clear shifts of isohyets and a slightly decreasing trend in extreme precipitation events. The result suggests that a negative trend in annual precipitation may have led to decreased soil erosion but an increase in sediment yield during several extreme events. These changes in the precipitation over the Loess Plateau should be noted, and countermeasures should be taken to reduce their adverse impacts on the sustainable development of the region. This article is protected by copyright. All rights reserved.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 4
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    Microbubble transport in water-saturated porous media (2015)
    Wiley
    Details
    Publication Date: 2015-05-21
    Description: Laboratory experiments were conducted to investigate flow of discrete microbubbles through a water-saturated porous medium. During the experiments, bubbles, released from a diffuser, moved upward through a quasi-2D flume filled with transparent water-based gelbeads and formed a distinct plume that could be well registered by a calibrated camera. Outflowing bubbles were collected on the top of the flume using volumetric burettes for flux measurements. We quantified the scaling behaviors between the gas (bubble) release rates and various characteristic parameters of the bubble plume, including plume tip velocity, plume width and breakthrough time of the plume front. The experiments also revealed circulations of ambient pore water induced by the bubble flow. Based on a simple momentum exchange model, we showed that the relationship between the mean pore water velocity and gas release rate is consistent with the scaling solution for the bubble plume. These findings have important implications for studies of natural gas emission and air sparging, as well as fundamental research on bubble transport in porous media. This article is protected by copyright. All rights reserved.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Contemporary condition and conservation of wetland resource in Pingshan, Hebei Province (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-08-31
    Description: The current work envisages the use of Remote sensing,Geography information systems and Global positioning systems literature analysis of precipitation, field investigation and laboratory analysis to perform a comprehensive investigation on the present situation of wetland resources of Pingshan Wetland in Hebei Province. The results showed that there were 5 types of wetlands, including the riverine wetland, flood plain, reservoir and pond, water-conveyance canal, and paddy field, with a total area of 162.61 km 2 . There were 311 species of wetland higher plants in Pingshan County, including 10 species of bryophytes, 296 angiosperm species, 5 species of ferns, and 81 phytoplankton species. There were 186 wetland birds, 35 species of fish, 5 species of amphibians, 14 species of reptiles, and 19 species of mammals in Pingshan County. In view of the present situation and the threat of wetland in Pingshan County, certain suggestions have been proposed to strengthen the protec...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 6
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    Power forecast research of photovoltaic system based on double-level neural network (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-10-31
    Description: A photovoltaic generation system is affected by many factors. The traditional method of forecasting photovoltaic power generation is more complicated. A double-level neural network is designed with consideration of these factors: the first level network calculates a real solar radiation with input of theory radiation and weather coefficient; the second level network calculates the final result generation power with input of real solar radiation which comes from the first network and the highest temperature which comes from weather forecast. The final power results indicate this method has good forecast capacity, calculate results are very close to measure value and errors are less than single level network.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 7
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    Modelling and simulation for installation feasibility of standalone photovoltaic system for Quetta, Pakistan (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-10-31
    Description: The impact and significance of renewable energy in developing countries is increasing rapidly in latest years. There is much need of energy dependence to be based on off grid photovoltaic systems in developing countries like Pakistan which are suffering from severe power shortfalls annually and load shedding concern. In this paper, a concept assessment and estimation of standalone photovoltaic system is done for the site of Quetta, Pakistan in comparison to the location of the Copiapo-Chamonate. Copiapo-Chamonate site is situated in Atacama Desert which is often labelled as the best solar irradiation receiving location in the world with maximum solar insolation reaching to 9.28 kWh/m 2 /day. The systems for both locations is modelled and simulated in PVSYST for a constant load of 11.9 kWh/day with seasonal tilt adjustment. According to the simulation, results of the parameters including performance ratio, solar fraction, energy supplied to the load etc. show that Quetta...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 8
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    Coordinated control of AGC with consideration PEVs and controllable loads in power system with renewable energy sources (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-10-31
    Description: According to the complementary nature of different power supplies, we proposed an optimal control system model based on model predictive control (MPC) in existing automatic generation control (AGC) framework to support effective operation of the AGC with the considerations of plug-in electric vehicles (PEVs) and controllable loads, to achieve full utilization of renewable energy sources, and to reduce the imbalance between supply and demand in the grid as far as possible. According to dynamics and update rate of power supplies at different time scales, as well as their actual power and energy constraints, MPC load distributor can find a solution of the MPC programming problem to well control the reserve capacities from the conventional generators, PEVs and controllable loads so that the tracking error of area control error (ACE) can be minimized. Massive simulation studies were performed under various control elements, such as different power combinations, different control rese...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 9
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    A cloudy planetary boundary layer oscillation arising from the coupling of turbulence with precipitation in climate simulations (2017)
    Wiley
    Details
    Publication Date: 2017-08-01
    Description: The Community Atmosphere Model (CAM) adopts Cloud Layers Unified By Binormals scheme (CLUBB) and an updated microphysics (MG2) scheme for a more unified treatment of cloud processes. This makes interactions between parameterizations tighter and more explicit. In this study, a cloudy planetary boundary layer (PBL) oscillation related to interaction between CLUBB and MG2 is identified in CAM. This highlights the need for consistency between the coupled sub-grid processes in climate model development. This oscillation occurs most often in the marine cumulus cloud regime. The oscillation occurs only if the modeled PBL is strongly decoupled and precipitation evaporates below the cloud. Two aspects of the parameterized coupling assumptions between CLUBB and MG2 schemes cause the oscillation: 1) a parameterized relationship between rain evaporation and CLUBB's sub-grid spatial variance of moisture and heat that induces an extra cooling in the lower PBL; and 2) rain evaporation which happens at a too low an altitude because of the precipitation fraction parameterization in MG2. Either one of these two conditions can overly stabilize the PBL and reduce the upward moisture transport to the cloud layer so that the PBL collapses. Global simulations prove that turning off the evaporation-variance coupling and improving the precipitation fraction parameterization effectively reduces the cloudy PBL oscillation in marine cumulus clouds. By evaluating the causes of the oscillation in CAM, we have identified the PBL processes that should be examined in models having similar oscillations. This study may draw the attention of the modeling and observational communities to the issue of coupling between parameterized physical processes.
    Electronic ISSN: 1942-2466
    Topics: Geography , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    The antioxidant activities of litchi pericarp among different cultivars (2017)
    Institute of Physics (IOP)
    Details
    Publication Date: 2017-08-06
    Description: The contents of total phenol and total flavonoid of 7 litchi pericarp cultivars were determined. Their antioxidant activities were also evaluated by 1,1-diphenyl-2-pireyhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP). Correlations between total flavonoid and DPPH scavenging capacity as well as FRAP were also analyzed. The results showed that litchi pericarp was rich in natural antioxidant compounds and the antioxidant abilities were different among different cultivars, and this was useful in the utilization of litchi processing waste.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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