oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
CORRELATION ANALYSIS OF NDVI WITH CLIMATE AND HYDROLOGICAL FACTORS IN OASIS AND DESERT
荒漠绿洲NDVI与气候、水文因子的相关分析

张远东,徐应涛,顾峰雪,潘晓玲
植物生态学报 , 2003,
Abstract: The interactions between vegetation and climate are always an important domain in ecological research. NDVI (Normalized difference vegetation index) is an important index that reflects the radiation_absorbing characteristic of vegetation and the climatic stress action. Since 1990, the relationships between NOAA/AVHRR NDVI and climatic factors have been studied in many papers and the relative conclusions in arid zones differ completely. It is very important to clear up the problem in the application of NDVI to eco_environmental monitoring and research in arid zones. By means of the digital NOAA/AVHRR NDVI images with 1 km spatial resolution and monthly climatic and hydrological data set in Fukang from 1992 to 1996, the correlation of NDVI with climate and hydrological factors are analyzed in oasis and desert respectively in this paper. NDVI images come from AVHRR database of United States Geological Survey, which have been treated with atmosphere rectification, cloud checkout, quality control and maximum value composite every ten days. NDVI images are registered to 0.3-0.7 pixel error according to the mountains and water system map in Xinjiang. Oasis NDVI is clipped with farm boundary in Fukang and desert NDVI is clipped with desert grassland boundary. Monthly NDVI mean values in oasis and desert are calculated respectively with Arcview 3.2. Climate indices include monthly precipitation, monthly maximum atmospheric temperature, monthly minimum atmospheric temperature, monthly average atmospheric temperature, monthly minimum relative humidity, monthly mean relative humidity and monthly sunlight hours. Hydrological indices include monthly surface runoff in Sangonghe basin and monthly mean water table in pluvial fan and alluvial plain. The correlation coefficients of NDVI with all climatic and hydrological factors are calculated with SPSS 10.0. The analysis shows that NDVI values in oasis have different rules of monthly variation from those in desert. Atmospheric temperature, groundwater table and precipitation are significantly correlative with NDVI in oasis, and irrigation is an important factor, which influences oasis NDVI. Correlation coefficients of desert sparse vegetation NDVI with oasis climatic and hydrological factors are insignificant and meaningless in ecological interpretation. In the process of analysis between NDVI and environmental factors in arid zones, the temporal and spatial scale must be strictly corresponding, oasis and desert must be considered respectively and conclusions from oasis NDVI are not adapted to the desert sparse vegetation. The contradictions in the conclusions of foregoing studies come from the confusion of application scope of their results, and the results of oasis NDVI can not represent the rules of the whole arid zone.
GPUs: An Oasis in the Supercomputing Desert  [PDF]
Waseem Kamleh
Physics , 2012,
Abstract: A novel metric is introduced to compare the supercomputing resources available to academic researchers on a national basis. Data from the supercomputing Top 500 and the top 500 universities in the Academic Ranking of World Universities (ARWU) are combined to form the proposed "500/500" score for a given country. Australia scores poorly in the 500/500 metric when compared with other countries with a similar ARWU ranking, an indication that HPC-based researchers in Australia are at a relative disadvantage with respect to their overseas competitors. For HPC problems where single precision is sufficient, commodity GPUs provide a cost-effective means of quenching the computational thirst of otherwise parched Lattice practitioners traversing the Australian supercomputing desert. We explore some of the more difficult terrain in single precision territory, finding that BiCGStab is unreliable in single precision at large lattice sizes. We test the CGNE and CGNR forms of the conjugate gradient method on the normal equations. Both CGNE and a modified form of CGNR (with restarts) provide reliable convergence for quark propagator calculations in single precision.
Impacts of inhomogeneous landscapes in oasis interior on the oasis self-maintaining mechanism by integrating numerical model with satellite data
X. Meng,S. Lu,T. Zhang,Y. Ao
Hydrology and Earth System Sciences Discussions , 2012, DOI: 10.5194/hessd-9-1979-2012
Abstract: Mesoscale meteorological modeling is an important tool to help understand the energy budget of the oasis. While basic dynamic and thermodynamic processes for oasis self-maintaining in the desert environment is well investigated, influence of heterogeneous landscapes of oasis interior on the processes are still important and remain to be investigated. In this study, two simulations are designed for investigating the influence of inhomogeneity. In the first case, land surface parameters including land-use types, vegetation cover fraction, and surface layer soil moisture are derived by satellite remote sensing data from EOS/MODIS, and then be used specify the respective options in the MM5 model, to describe a real inhomogeneity for the oasis interior. In the other run, land use types are set to MM5 default, in which landscapes in the oasis interior is relative uniform, and then surface layer soil moisture and vegetation fraction is set to be averages of the first case for the respective oasis and desert surface lying, to represent a relative homogeneity. Results show that the inhomogeneity leads to a weaker oasis "cold-wet island" effect and a stronger turbulence over the oasis interior, both of which will reduce the oasis-desert secondary circulation and increase the evaporation over the oasis, resulting in a negative impact on the oasis self-protecting mechanism. The simulation of homogeneity indicates that the oasis may be more stable even with relative lower soil moisture if landscapes in the oasis interior are comparatively uniform.
Human-induced spatio-temporal changes of oasis through landscape pattern analysis:a case study of oasis in the Sangong River
从景观格局分析人为驱动的绿洲时空变化——以天山北坡三工河流域绿洲为例

LUO Geping,ZHOU Chenghu,CHEN Xi,
罗格平
,周成虎,陈曦

生态学报 , 2005,
Abstract: Among landscape changes, a particular type is the landscape change in an oasis that is isolated in desert surroundings. Due to the available groundwater and runoff from nearby high mountains, oasis areas have higher productivity than the surrounding desert. The landscape changes in oases have been a major concern in Xinjiang province, China. In the past 50 years, large-scale land reclamation and cultivation of water resources in Xinjiang have resulted in tremendous changes in the oases. We have investigated...
The Oasis and Desert Effect in a Simple Dynamics Model of Interaction between Oasis and Climate
一个简单陆气耦合模式中的绿洲-荒漠化效应

Wu Lingyun,Chao Jiping,
吴凌云
,巢纪平

气候与环境研究 , 2004,
Abstract: In this paper, we construct a coupled system of oasis and atmosphere based on an oasis evolvement model by adding atmospheric motion to discuss how different climate and vegetation type have the effect on oasis. The results indicate: lower latitude, smaller horizontal scale, lower humidity and some vegetation with small stoma resistance are good to develop oasis. The simple conclusions are helpful to develop complex number model and deal with desert.
Numerical simulation of land-atmosphere interaction and oasis effect over oasis-desert
沙漠-绿洲陆-气相互作用和绿洲效应的数值模拟

Liu ShuHua,Hu Yu,Hu Fei,Liang FuMing,Wang JianHua,Liu HePing,
刘树华
,胡予,胡非,梁福明,王建华,刘和平

地球物理学报 , 2005,
Abstract: We use a developed parameterized scheme of land surface processes and a transfer model to simulate the physical process of land surface and the interaction between the land surface and the atmosphere boundary layer over an oasis-gobi inhomogeneous area in a semi-arid region. Structure features of vertical section are given more clearly and carefully. The results of numerical simulation are in accord with the previous observations. The results show that the oasis effect has clear cold island effect and wet island effect. It displays that environmental temperature is lower, humidity is higher and the energy of turbulent momentum transfers weakly over oasis than over desert, and there are circulations between oasis and desert. Making more detailed studies on these phenomena is of great significance to understanding of the formation of oasis climate and sustaining mechanisms of oasis.
Impacts of inhomogeneous landscapes in oasis interior on the oasis self-maintenance mechanism by integrating numerical model with satellite data
X. Meng, S. Lu, T. Zhang, Y. Ao, S. Li, Y. Bao, L. Wen,S. Luo
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2012,
Abstract: The impacts of inhomogeneity of the oasis interior on the oasis self-maintenance mechanism are investigated by using the mesoscale model MM5 (the fifth-generation Pennsylvania State University National Center for Atmospheric Research (NCAR) mesoscale model) with satellite observations of land use types, vegetation fraction and surface-layer soil moisture from MODIS (Moderate Resolution Imaging Spectroradiometer) data. Four simulations were performed, among which the CTL (control simulation) and MOD (moderated simulation with parameters replaced by MODIS data) were used to validate the model results; EXP1 (experiment 1) and EXP2 (experiment 2) were designed to study the inhomogeneity of oasis interior. Results show that the changes of oasis heterogeneity influence the surface heat-flux partitioning, which leads to a larger "cold-wet" effect over the oasis. Vertical sections of humidity illustrate the existence of a moisture-inversion level, and the deeper moisture inversion of EXP1 and EXP2 further indicates that the relative homogeneity in the oasis interior helps produce stronger humidity inversion over the oasis, thus limiting evaporation. This is further verified by the analysis of the secondary circulation, which shows that the more homogeneous land surface conditions lead to stronger secondary circulation and less turbulent drafts over the oasis interior, playing a positive role in the oasis self-maintenance and development.
Warming effect of desert and its impact on oasis heat resources and agricultural productivity in arid land, China

FengHua Zhang,Qiang Zhao,Munir A Hanjra,

寒旱区科学 , 2012,
Abstract: This paper provides a positive view of the desert, in terms of the warming effect of deserts on oases and the impact of heat resources and agricultural production. We use data from experimental sites in the Manas River Basin in China to characterize these relationships. We note that the warming effect of the desert was found to be significant but gradually reduced with increased distance of the oasis from the desert. The range of warming effect is about 100 km, and the improvement in temperature is about 1.8 °C. Due to this warming effect, the desert serves as the second heat source for the oasis, which represents one important aspect of the ecologic value of the desert. Our results also show the warming effect has a strong spatial impact on agricultural productivity. Crop productivity fell by about 49 kg/ha with every 10 km increase in distance away from the desert. Our results imply that crop suitability must correspond to the warming effect of the desert. More efficient use of heat resources can contribute towards achieving potential productivity.
Researches on laws of water balance at transitional zone between oasis and desert in Minqin
民勤绿洲-荒漠过渡区水量平衡规律研究

WANG Bing,CUI Xianghui,
王兵
,崔向慧

生态学报 , 2004,
Abstract: Research area was located in the oasis-desert intermediate zone on the other edge of Liujiadi Village in Minqin Country, at the transitional belt between Badanjilin desert and Tenggeli desert, where a 2 km sample belt, was established, along the prevailed direction of wind causing desertification. With 3 different gradient types of vegetation coverage (Tamarix ramosissima shrub sand dune, Nitraria sibirica shrub sand dune and shifting sand dune) as the research subjects, such ecological factors as water, so...
Estimation Model of Oasis Heat Resources under Warming Effect of Desert in Junggar Basin
沙漠增温效应下绿洲热量资源估算模型——以准噶尔盆地为例

ZHANG Feng-hua,ZHAO Qiang,
张凤华
,赵强

中国沙漠 , 2011,
Abstract: Oasis is the most essential area of desert eco-system in arid and semi-arid regions.During warm season,heat resource of the oasis is more superior than other region in the same latitude due to the warming effect of the desert.Taking the Gurbantunggut Desert and the Shihezi Oasis in the Junggar Basin as an example,the temporal-spatial distribution and changes of oasis heat resources under warming effect of desert were analyzed.A warming coefficient(Z) was put forward to reflect the sensitivity of oasis tempe...
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.