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1.
森林-水资源系统的理论分析   总被引:1,自引:2,他引:1  
本文认为,应当从森林-水资源系统出发研究森林与水资源的关系。并提出了一个分析森林-水资源系统产流过程的仿真模拟方法,得出在一定条件下,有森林植被的地方可能会比无森林植被的地方产生更多的能够为人类所利用的水资源的结论;进一步提出了构成最佳水资源生成系统的四项条件。作者分析了森林对降雨的影响,认为二次降雨和水平降雨对水资源量的直接影响很小;由于森林是大气的特殊下垫面具有软边界和强烈的物质能量变换的特点,加之森林蒸散的水汽和释放的凝结核等因素,可能会影响大气垂直降雨的空间分布,或提高产生降雨的可能性,从而使有林地区有增雨效果。最后对森林-水资源的研究方法提出了几点建议。  相似文献   

2.
In a natural atmosphere free from anthropogenic emissions, terpenes constitute a major part of the biogenic hydrocarbon family. The study of their involvement in chemical reactions with various oxidants in the atmosphere requires continuous and accurate checking of their diurnal concentration variations. In past studies, the ever present sample preconcentration step with large sample volumes is expected to be associated with the problems of sample loss or chemical modifications in addition to their limitations on the measurement frequency. To improve upon these drawbacks, a commercially available microprocessor-based portable gas chromatograph with an ultra-sensitive detector was successfully tested and used for in situ measurements. With a direct sample volume of a few hundred microlitres of ambient air and suitable selection of the column packing material, quick separation of the various components was achieved. Excellent operational features and on-line calibration with pure samples allowed accurate and instant measurements during field studies. The photoionization (PI) detector allowed high S/N ratio even at sub-parts per billion level concentration of the hydrocarbons. Data collected over a one-year period under varying meteorological conditions from a conifer forest situated at Gulmarg (34°03′N, 74°24′E, 2650 m MSL) indicates the suitability of this system for remote field studies and also throws light on the lifecycle of these hydrocarbons in the natural atmosphere. The different hydrocarbons measured in this evaluation study includes isoprene, α-pinene and β-pinene.  相似文献   

3.
大气二氧化碳含量正在以每年0.4%的速度增加,对森林产生越来越明显的影响,对未来林业提出七个方面的挑战:温度变化、水的变化、气候变化、虫害和火灾变化、新基因的需要、造林与经营、加速研究进程,对此应尽快作出估价。  相似文献   

4.
The present state of knowledge of organic, or carbon-based, peroxy radicals (RO2) is reviewed. Data on the chemical and physical properties of peroxy radicals in the gas-phase is considered, as well as the role of peroxy radicals in tropospheric chemistry and measurements of their concentrations in the atmosphere. Where appropriate, peroxy radicals are grouped together by type (alkyl, acyl, oxygen-substituted, halogen-substituted and aromatic radicals) to facilitate comparison. Data on the hydroperoxy radical (HO2) is included where it is directly relevant to measurements on organic peroxy radicals, eg. absorption cross-sections used in measurements of RO2 + HO2 rate constants. The literature data is critically reviewed and recommendations for absorption cross-sections, rate constants and branching ratios are made where considered appropriate.The laboratory experimental techniques which have been used for the generation and detection of peroxy radicals and the products of their reactions are discussed. The structure, spectroscopy and thermochemistry of the radicals are examined. Although the majority of spectroscopic data concerns the u.v. spectra much used for kinetic studies, near-infrared, infrared and electron spin resonance spectra are also considered. In many cases, peroxy radical u.v. spectra are well-fitted by a Gaussian distribution function, enabling the cross-sections to be easily calculated at any wavelength.For the purpose of this review, the chemical reactions of peroxy radicals are divided into reactions with organic peroxy radicals with HO2, with NO and NO2, and finally with other species. Peroxy radical abstraction and addition reactions with closed-shell species are sufficiently slow to be of negligible importance at temperatures pertinent to the atmosphere and are consequently not covered. Data on both the kinetics and mechanisms of peroxy radical reactions are considered.The role of peroxy radicals as intermediates in the atmospheric degradation of volatile organic compounds and in the production of ozone in the troposphere under both low and high [NOx] conditions is discussed. The involvement of peroxy radicals in night-time oxidation chemistry and the oxidation of halocarbons is also indicated. The techniques used for the difficult measurement of peroxy radical concentrations in the atmosphere are described, together with the results to date.Finally, some tentative suggestions as to further avenues of research are made, based on the data reviewed here and with particular reference to the solution of outstanding problems in atmospheric chemistry. Although a great deal of progress has been made in recent years, it is clear that additional work is needed in most areas covered by this review. New, sensitive and selective laboratory techniques are required for studies of peroxy radical kinetics and high level ab initio calculations would help design laser-based detection techniques. Further product studies of photooxidation systems are needed, particularly as a function of temperature. Recent work has shown that the rate constants for RO2 + HO2 reactions used in modelling studies may be too low; if so, these reactions will be correspondingly more important than previously believed in tropospheric oxidation. Recent kinetic studies of the potentially important reactions of methylperoxy radicals with ClO and NO3 need to be confirmed and mechanistic work is necessary. Although substantial progress has been made towards the monitoring of peroxy radical concentrations in the atmosphere, more work is needed, both on measurements and the development of new techniques.  相似文献   

5.
This review surveys the present state of knowledge of the nitrate (NO3 radical. Laboratory data on the physics and chemistry of the radical and atmospheric determination of the concentrations of the radical are both considered. One aim of the review is to highlight the relationship between the laboratory and the atmospheric studies. Although the emphasis of the review is on gas-phase processes, relevant studies conducted in condensed phases are mentioned because of their potential importance in the interpretation of cloud and aerosol chemistry.The spectroscopy, structure, and photochemistry of the radical are examined. Here, the object is to establich the spectroscopic basis for detection of the radical and measurement of its concentration in the laboratory and in the atmosphere. Infrared, visible, and paramagnetic resonance spectra are considered. An important quantity discussed is the absorption cross section in the visible region, which is required for quantitative measurements. Interpretation of the spectroscopic features requires an understanding of the geometrical and electronic structure of the radical in its ground and excited states; there is still some controversy about the groundstate geometry, but the most recent experimental evidence 9eg from laser induced fluorescence) and theoretical calculations suggest that the radical has D3h symmetry. Photodissociation of the radical is important in the atmosphere, and the product channels, quantum yields, and dissociation dynamics are discussed. A short examination of the thermodynamics (heat and entropy of formation) of the radical is presented.The main exposition of laboratory studies of the chemistry of the nitrate radical is preceded by a consideration of the techniques used for kinetic and mechanistic studies. Methods for the generation and detection of the radical and the kinetic tools employed are all presented. The exact nature of the technique used in individual studies has some relevance to the way in which data must be analysed, and to the type of mechanistic information that can be extracted. Continuous and stopped flow, flash photolysis and pulse radiolysis, molecular modulation, and static reactor techniques can all provide absolute kinetic data, while relative rate measurements have been a further rich source of information.The treatment of the chemical reactions of the nitrate radical is formally divided into the interactions with non-radical inorganic (deemed to include NO and NO2) and organic species, and with atoms and free radicals. In general, the reactions with open-shell species are much more rapid than those with closed-shell reactants. With the closed-shell partners, addition reactions are faster than abstraction reactions. An attempt is made to consider critically the published data on most reactions of importance, and to tabulate rate constants and temperature dependences where possible. However, it is not the objective of this review to provide recommendations for rate parameters. Evidence for the products of the reactions is sought, and for the branching ratios into the various channels where more than one exists. One theme of this part of the review is the elucidation of correlations of reactivity with structure and with the reactions of other radical species such as OH.The review turns next to a consideration of the role of NO3 in the atmosphere, of its atmospheric sources and sinks, and of field measurements of concentrations of the radical. Long-path visible-absorption spectroscopy and matrix-isolation ESR have both been used successfully in field measurements in the troposphere as well as the stratosphere. Balloon-borne instruments and ground-based remote sensing have been used to obtain stratospheric concentrations. Two of the most important implications of the measurements are that the stratospheric profiles are consistent with accepted chemistry (and, in particular, do not require the postulation of an unidentified scavenging mechanism that had, at one stage, been proposed), and that the highly variable night-time tropospheric concentrations imply that NO3 is a reactive tropospheric constituent. The inter-relation between laboratory studies and atmospheric observations, and the problems in extrapolating laboratory data to atmospheric conditions, are both explored. Initiation of night-time chemical transformations by NO3 and the possible production of OH are considered. The available information is then brought together to see how far NO3 is a sensitive indicator of the state of the atmosphere, and some speculations are presented about the involvement of NO3 (or N2O5) in damage to trees and plants.The final section of the review suggests some issues that remain unresolved concerning the NO3 radical which is directly or indirectly relevant to a better knowledge of the part played by the radical in the atmosphere. Amongst the requirements noted are improved data for the heat of formation of the radical, its absorption cross section in the visible region (and, especially, the temperature dependence of the cross section), and the details of its photochemistry. There is also still a need for a definitive determination of the equilibrium constant and its temperature dependence for the association with NO2 and the reverse dissociation of N2O5. A series of chemical reactions deserves further investigation, especially with regard to elucidation of product channels, and overall oxidation mechanisms also need to be defined better. Future atmospheric studies that are desirable include study of basic NO3 chemistry in the field to understand the influence of humidity on the conversion (probably on surfaces) of N2O5 to HNO3, and thus on NO3 concentrations. In addition, a study of the chemistry of NO3 in the presence of volatile organic compounds and at elevated concentrations of the oxides of nitrogen should help in the understanding of, for example, polluted marine coasts, forests, and urban areas.  相似文献   

6.
Throughfall measurements are very often used to calculate the atmospheric input to ecosystems. Such attempts are normally complicated by canopy interaction processes which are difficult to assess. This study presents an approach to calculate dry deposition and canopy leaching of Ca2+, Mg2+ and K+ to forests. The calculations are based on throughfall measurements in a forest edge of a spruce stand and by use of Na+ as a model substance for dry deposition of particles. This ‘forest edge approach’ is compared with an approach based on equal Na+ to base cation ratios in wet and dry deposition (‘wet/dry ratio approach’), which has been widely used in the literature. Our calculations show that the wet/dry ratio approach may overestimate the dry deposition of Ca2+, Mg2+ and K+ by up to 100% and leaching will correspondingly be underestimated. The assumptions underlying the different approaches and the use of throughfall measurements to estimate dry deposition are discussed and it is suggested that throughfall measurements in forest edges may be a valuable improvement to studies of atmospheric deposition in forests.  相似文献   

7.
Sex ratios of ants have been shown to vary with food resource levels in several studies, but it is not known whether forest clear-cutting has any effect on sex ratio of aphid-tending forest-dwelling ants. We investigated whether the offspring sex ratio of the forest dwelling ant Formica aquilonia varied as a response to clear-cutting. We found that the proportion of males was smaller in clear-cuts than in adjacent forests. Our results are among the first showing that anthropogenic changes in forest structures may have a potential to modify sex ratios of social insects and other forest-dwelling animals.  相似文献   

8.
Although many factors influencing the forest C cycle are beyond direct human control, decisions made in forestry and the forest product sector (FPS) can either mitigate or aggravate the net C balance of terrestrial ecosystems. The Canadian Budget Model of the Forest Product Sector (CBM-FPS) described here, was designed to work with a national scale model of forest ecosystem dynamics (the Carbon Budget Model of the Canadian Forest Sector, CBM-CFS). The CBM-FPS accounts for harvested forest biomass C from the time that it enters the manufacturing process until it is released into the atmosphere. It also accounts for the use and production of energy by the FPS, and emission of CO2 during FPS processing. The CBM-FPS accounting framework uses the characteristics of different forest product types to estimate changes in the storage of C in forest products; it tracks C from the transportation of the harvested raw material through various processing steps in sawmills or pulp mills, to its final destination (product, pulp, landfill, atmosphere or recycled). Because not all harvested biomass C is released into the atmosphere in the year it is harvested, the model tracks C retained in various short- and long-lived products, and in landfills. Model results are in general agreement with available data from 1920–1989. Average changes in net C stocks in the FPS, estimated as the difference between harvest C input to the FPS and total losses from the forest product sector is estimated to be 23.5 Tg C yr−1 for the 1985–1989 period. The total FPS pool size at the end of this period is estimated to be 837 Tg C, of which only a fraction (32%) is retained in Canada. The total FPS C stock is small compared to that in the forest ecosystems from which they derive (estimated to contain 86 Pg C in 1989). Nevertheless, the changes in these C stocks contribute significantly to a reduction of the total net atmospheric exchange of the total forest sector (ecosystem and product sector) for that period.  相似文献   

9.
海洋微表层化学研究进展   总被引:4,自引:1,他引:4  
海洋微表层是具有独特物理、化学、生物性质的海层,海-气间物质和能量交换的界面,许多物质如营养盐、有机物、痕量金属、微生物在海洋微表层中都有不同和蔼的富集作用本文概述了国内外有关海洋微表层研究的主要成果,并对进一步的研究领域提出了看法。  相似文献   

10.
The effect of concentration fluctuations on the modelling of non-linear chemical reactions in the atmosphere will be considerable when hourly mean dispersion parameters are used. This effect can be reduced by introducing instantaneous dispersion parameters, as will be shown in this paper for the modelling of the oxidation of NO emited into an O3 containing atmosphere.We used the results of atmospheric tracer gas experiments to derive the dimensions of the instanteneous plume. With these results model calculations were carried out for the NOO3 reaction. Results were compared with airborne measurements of NO oxidation in the plumes of Dutch power plants.The introduction of the instantaneous plume leads to better agreement between model calculations and measurements. It is also found that the deviation from photochemical equilibrium in the plume is considerably smaller when instantaneous, instead of hourly, mean dispersion parameters are used. The dimension of the instantaneous plume did not show a dependence on atmospheric stability.  相似文献   

11.
总结了环境大气中半/中等挥发性有机物(S/IVOCs)的主要测量技术及其进展,重点介绍了基于气相色谱技术和化学电离质谱技术的测量方法.S/IVOCs的测量主要由气相色谱技术开始发展,并随着质谱技术的发展而不断发展.基于气相色谱技术的测量方法,能够直接测量非极性化合物,但在面对组分多达千万种的复杂体系时,传统的一维色谱相对耗时,而且由于峰容量不够,峰重叠现象十分严重,难以实现全组分的准确分离.新近发展的多维分离系统如全二维气相色谱,通过正交的分离系统,能够实现复杂体系中物种组分的准确、快速分离.目前基于化学电离质谱技术的在线测量方法已经逐渐应用于S/IVOCs的测量,虽然在物种定性方面相对较弱,但其可提供高时间分辨率的测量结果,帮助分析S/IVOCs在大气中的快速变化.在未来的研究中,高时间分辨率和全组分准确测量是S/IVOCs研究的关键.  相似文献   

12.
总结了环境大气中半/中等挥发性有机物(S/IVOCs)的主要测量技术及其进展,重点介绍了基于气相色谱技术和化学电离质谱技术的测量方法.S/IVOCs的测量主要由气相色谱技术开始发展,并随着质谱技术的发展而不断发展.基于气相色谱技术的测量方法,能够直接测量非极性化合物,但在面对组分多达千万种的复杂体系时,传统的一维色谱相对耗时,而且由于峰容量不够,峰重叠现象十分严重,难以实现全组分的准确分离.新近发展的多维分离系统如全二维气相色谱,通过正交的分离系统,能够实现复杂体系中物种组分的准确、快速分离.目前基于化学电离质谱技术的在线测量方法已经逐渐应用于S/IVOCs的测量,虽然在物种定性方面相对较弱,但其可提供高时间分辨率的测量结果,帮助分析S/IVOCs在大气中的快速变化.在未来的研究中,高时间分辨率和全组分准确测量是S/IVOCs研究的关键.  相似文献   

13.
叶面积指数(LAI) 是森林经营管理的一个重要参数,亦是众多基于土壤、大气和植被相互作用的森林经营管理动态模型的关键输入变量之一,但目前获得大尺度、高空间分辨率的LAI精确估计仍十分困难。以川西南山地常绿阔叶林为研究对象,基于地面调查的83 个20 m×20 m样地和SPOT5 遥感数据,运用不同的方法,估测了区域森林有效叶面积指数(LAIe)。利用遥感数据作为辅助变量,比较了来自遥感数据的直接辐射关系法(DRR) 和地统计学方法协同克里格(CK)、回归克里格(RK) 的LAIe 空间分布差异。此外,运用反距离权重(IDW)、全局多项式(GPI)、普通克里格(OK)、泛克里格(UK) 等方法也对LAIe进行了估计。结果表明LAIe 与归一化植被指数(NDVI) 回归拟合效果相对不理想(R2=0.679,P<0.001);由于研究区森林景观不是连续变量,LAIe呈低空间自相关性,各方法间差异不显著,对区域LAIe 估算精度提升不明显;但DRR 和CK、RK 方法能降低统计误差值,且DRR与CK、RK的相关性极高(相关系数分别可达0.91和0.92)。尽管相比于DRR,地统计学方法并没有提高LAIe估计精度,为提高预测的准确性,应探讨更密集的抽样方案和不同的辅助变量。  相似文献   

14.
CaF2高温分解特性试验研究   总被引:1,自引:0,他引:1  
作为燃煤和砖瓦烧制过程中钙基固氟剂燃烧固氟的最终产物CaF2,其高温稳定特性对固氟效率有重要影响本义在固定床反应器上采用气态氟化物直接吸收分析法,结合XRD、DTA法对CaF2晶体粉末在大气、干燥大气和饱和大气下的高温稳定性进行了实验研究.结果表明,在高温条件下CaF2发生水解反应,水解反应起始温度830±10℃,水解率随燃烧温度和停留时间的增加而增加,空气中水蒸气含量对水解率有显著影响.动力学计算表明温度在850℃~1350℃范围内水解反应为一级反应,反应活化能E=115±2kJ/mol.研究结果对燃煤和砖瓦烧制过程中高温高效钙基燃烧固氟剂的开发有指导意义.  相似文献   

15.
张家界森林大气中醛酮类化合物浓度变化特征   总被引:6,自引:3,他引:3       下载免费PDF全文
为探究中亚热带森林大气中醛酮类化合物浓度变化特征,于2014年8月—2015年1月在张家界森林公园采用 EPA TO-11A方法对张家界森林大气中醛酮类化合物质量浓度进行了监测.结果表明:张家界森林大气中主要的醛酮类化合物为甲醛、乙醛、丙酮、丙醛和MACR(甲基丙烯醛),质量浓度分别为4.32、0.95、3.01、0.48和0.51 μg/m3.大气中ρ(甲醛)、 ρ(乙醛)和ρ(MACR)的季节变化特征很明显,夏季和秋季醛酮类化合物质量浓度较高,冬季醛酮类化合物质量浓度较低.此外,醛酮类化合物质量浓度日变化显著,除了10月、12月受人为因素影响较大外,其余月份醛酮质量浓度最大值通常出现在13:00—15:00.张家界森林大气中C1/C2(ρ(甲醛)/ρ(乙醛))为5.72,比城市地区(C1/C2为1左右)高,但比偏远森林地区(C1/C2为10左右)低.ρ(甲醛)与ρ(乙醛)、 ρ(MACR)均呈正相关且达到显著水平,而ρ(丙酮)与ρ(甲醛)、 ρ(乙醛)与ρ(MACR)的相关性差.与文献报道的加拿大Ontario、墨西哥Langmuir等地区对比,张家界森林大气中醛酮类化合物质量浓度较高,但明显低于北京、上海等城市地区.研究显示,张家界森林大气中甲醛、乙醛和MACR主要来自森林地区植物排放的VOCs光氧化生成,丙酮除了来自植物排放的有机物光氧化分解外,还有其他人为源,进一步说明了张家界森林大气中醛酮类化合物浓度变化主要受光化学反应等自然影响,但人为因素的影响也不容忽略.   相似文献   

16.
西部地区植被恢复重建中几个问题的思考   总被引:44,自引:2,他引:44  
以退耕还林还草为主体的西部地区植被恢复重建是一项复杂的生态-经济复合系统工程,必须以水热等气候因子所决定的植被生物地带性为科学依据,以国家调控下的区域间互补的市场经济机制为运作体系,必须在建立长期稳定的经济补偿机制的同时,建立长期稳定的政策和法律保障体系。为此,该文讨论了西部地区自然植被的地理格局、适度的退耕规模和退耕后的植被恢复重建、植被恢复工程的环境服务功能产出、生态产业与经济补偿机制、天然植被的保护和改良等科学问题,指出了退耕还林还草试点工程中所存在的一些错误认识和不良倾向。  相似文献   

17.
Two approaches are frequently mentioned in proposals to use tropical forest maintenance as a carbon offset. One is to set up, specific reserves, funding the establishment, demarcation, and guarding of these units. Monitoring, in this case, consists of the relatively straightforward process of confirming that the forest stands in question continue to exist. In Amazonia, where large expanses of tropical forest still exist, the reserve approach has the logical weakness of being completely open to “leakage”: with the implantation of any given reserve, the people who would have been deforesting in the reserve area will probably continue to clear the same amount of forest somewhere else in the region. The second approach is through policy changes aimed at reducing the rate of clearing, but not limited to specific reserves or areas of forest. This second approach addresses more fundamental aspects of the tropical deforestation problem, but has the disadvantages of not assuring the permance of forest and of not resulting in a visible product that can be convincingly credited, to the existence of the project. In order for credit to be assigned to policy change projects, functioning models of the deforestation process must be developed that are capable of producing seenarios with and without different policy changes. This requires understanding the process of deforestation, which depends on monitoring in order to have information as a time series. Information is needed both from satellite imagery and from on-the-ground observations on who occupies the land and why the observed changes occur. Monitoring must be done by individual property if causal factors are to be identified reliably; this is best achieved using a database in a Geographical, Information System (GIS) that includes property boundaries. Once policy changes are made in practice, not only deforestation but also the policies themselves must be monitored. Deerees and laws are not the same as changes in practice; the initiation and continued application of changes must therefore be confirmed regularly. The value of carbon benefits from Amazonia depends directly on the credibility and transparency of monitoring. The great potential value of carbon maintenance in Amazonia should provide ample reason for Amazonian countries to strengthen and increase the transparency of their monitoring efforts.  相似文献   

18.
唐常春  樊杰  陈小良 《自然资源学报》2012,27(10):1645-1655
论文以长株潭生态绿心暮云镇为例,基于地域功能及其格局视角,采用整体协调性(C1)和有效协调性(C2)等指标,分析土地利用现状态势与地域功能规划的数量协调性、 空间协调性、 主要协调问题及效应。研究结果表明:暮云镇生态空间C1为54%,C2为69.81%,存在较大缺口,应新增面积高达802.95 hm2,绿心建设任重道远,需重点加强东北部-东部山林生态和北部绿带建设;农业空间C1为38.08%,C2为91.28%,转换潜力较大,但应加强区内土地整理和村庄整治,提升生产效能和生态服务功能;建设空间C1为36.11%,C2为82.94%,增长速度过快,威胁生态绿心功能定位及格局形成,扩展速度与空间布局亟需优化调整。研究区应实行功能空间三重保障、 统筹城乡人口与用地、 建设适度复合功能空间及构建区域协调长效机制,促进土地利用与地域功能协调发展。  相似文献   

19.
自然状态下树木排放N2O的研究   总被引:7,自引:3,他引:7  
大气中主要温室气体之一N2O的部分来源尚不清楚,以前认为只有土壤微生物过程是N2O的生物源,本文则旨在证明自然状态下植物也是N2O的排放源.采用同步空气样品采集装置和气相色谱仪观测了长白山阔叶红松林内空气N2O的垂直分布特征,发现林冠或其附近处出现高N2O浓度,高N2O浓度比同一时刻其他高度处的正常N2O浓度高3.03%~64.9%,差异显著或极显著.在林冠高度处的高N2O浓度和树干高度处的正常N2O浓度同时存在的现象证明了植物向外排放N2O,即植物自身在自然状态下是N2O的一个排放源.  相似文献   

20.
Five new towns have been developed around the Seoul metropolitan area since 1996. However, these new towns generate lots of traffic and related problems in the areas including those new towns and Seoul as a result of increases in population and a lack of ecological-self-sufficiency. Currently, construction of another new town is under deliberation, and what should be a major consider is the notion that the new town be located within a wide, green zone. Many studies have revealed that green space can play an important role in improving urban eco-meteorological capability and air quality. In order to analyze the urban heat island which will be created by the new urban development, and to investigate the local thermal environment and its negative effects caused by a change of land use type and urbanization, Landsat TM images were used for extraction of urban surface temperature according to changes of land use over the last 15 years. These data are analyzed together with digital land use and topographic information. As a study result, it was found the urban heat island of the study area from 198.5 to 1999 rapidly developed which showed a difference of mean temperature above 2.0. Before the Bundang new town construction the temperature of the residential area was the same as a forest, but during the new town construction in 1991 analysis revealed the creation of an urban heat island. The temperature of a forest whose size is over 50% of the investigation area was lowest, and thus the presence of a forest is believed to have a direct cooling effect on the urban environment and its surroundings. The mean temperature of the residential and commercial areas in the study was found to be 4.5 higher than the forest, and therefore this part of land use is believed to be the main factor causing the temperature increase of the urban heat island.  相似文献   

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