Study of statistically correcting model CMAQ-MOS for forecasting regional air quality     

XU Jianming  XU Xiangde  LIU Yu  DING Guoan  CHEN Huailiang  HU Jiangkai  ZHANG Jianchun  WU Hao  LI Weiliang  HE Jinhai  YANG Yuanqin  WANG Jiahe 《中国科学D辑(英文版)》2005,48(Z2)

Based on analysis of the air pollution observational data at 8 observation sites in Beijing including outer suburbs during the period from September 2004 to March 2005, this paper reveals synchronal and in-phase characteristics in the spatial and temporal variation of air pollutants on a city-proper scale at deferent sites; describes seasonal differences of the pollutant emission influence between the heating and non-heating periods, also significantly local differences of the pollutant emission influence between the urban district and outer suburbs, i.e. the spatial and temporal distribution of air pollutant is closely related with that of the pollutant emission intensity. This study shows that due to complexity of the spatial and temporal distribution of pollution emission sources, the new generation Community Multi-scale Air Quality (CMAQ) model developed by the EPA of USA produced forecasts, as other models did, with a systematic error of significantly lower than observations, albeit the model has better capability than previous models had in predicting the spatial distribution and variation tendency of multi-sort pollutants. The reason might be that the CMAQ adopts average amount of pollutant emission inventory, so that the model is difficult to objectively and finely describe the distribution and variation of pollution emission sources intensity on different spatial and temporal scales in the areas, in which the pollution is to be forecast. In order to correct the systematic prediction error resulting from the average pollutant emission inventory in CMAQ, this study proposes a new way of combining dynamics and statistics and establishes a statistically correcting model CMAQ-MOS for forecasts of regional air quality by utilizing the relationship of CMAQ outputs with corresponding observations, and tests the forecast capability. The investigation of experiments presents that CMAQ-MOS reduces the systematic errors of CMAQ because of the uncertainty of pollution emission inventory and improves the forecast level of air quality. Also this work employed a way of combining point and area forecasting, i.e. taking the products of CMAQ for a center site to forecast air pollution for other sites in vicinity with the scheme of model products "reanalysis" and average over the "area".  相似文献   

The diurnal and seasonal characteristics of urban heat island variation in Beijing city and surrounding areas and impact factors based on remote sensing satellite data     

ZHANG Jiahua  HOU Yingyu  LI Guicai  YAN Hao  YAO Fengmei 《中国科学D辑(英文版)》2005,48(Z2)

Based on the land surface temperature (LST), the land cover classification map,vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains,especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4-6℃ between Beijing city and suburb areas, comparatively is 8- 10℃ between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously negative.The scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.6481).The results demonstrate that the vegetation greenness is an important factor for reducing the UHI,and large-scale construction of greenbelts can considerably reduce the UHI effect.  相似文献   

山东泰安朱家庄自然硫矿床地质概要     

郝尔宏 《化工矿产地质》2005,27(3):129-138,149

山东省泰安朱家庄自然硫矿床,赋存于鲁西断隆古近纪汶东陆相盆地。自然硫矿层在汶口组二段上亚段,泥质灰岩-含泥灰岩-含云灰岩-石膏岩韵律层中的白云岩-石膏岩层段发育。自然硫以胶态、晶态、土态3种形态产出,可划分为顺层型、准顺层型、斑杂型及不顺层型4大类10余种矿石类型。从矿区去膏化作用普遍、自然硫与石膏-硬石膏分别富集轻-重同位素的特征、油气显示明显及地下水主要径流方向自然硫矿化最强等各种证据,表明该矿属生物后生成因的矿床。  相似文献   

Analysis on Bearing Capacity of Tunnel-Type Anchorage of a Long-Span Suspension Bridge     

Zhu Yu Wei Jun Yang Manjuan Li Hao Liu Hongqing 《中国地质大学学报(英文版)》2005,16(3):277-282

INTRODUCTION Tunnel typeanchoragehasobviousadvantages inbearingcapacityversusinvestment(LiuandHu,1996).However,itisrarelyusedinapracticalpro jectbecauseofitsrequirementofgoodrockcondi tions.Siduhebridge(Fig.1),whichliesintheBa dongmountainsinthewestplatea…  相似文献   

黄土区人类活动影响下的 产汇流模拟研究   总被引：4，自引：0，他引：4  

池宸星  郝振纯  王玲  胡健伟 《地理科学进展》2005,24(3):101-108

日益频繁的人类活动改变了流域下垫面条件,对流域产汇流产生很大的影响。本文以黄河中游典型支流岔巴沟为研究区域,提出利用基于DEM的分布式水文模拟技术,探讨流域人类活动过程中的产汇流模拟,避免了经验公式的概化和由此引起的局限。模拟的结果证实了该方法的可行性。采用网格滞蓄的方法可以在子网格上体现人类活动引起的下垫面的变化及其对产汇流的影响,反映各个时期的产汇流条件,对降雨做出合理响应。  相似文献   

浙江磐安蕨类植物资源及其开发利用   总被引：5，自引：0，他引：5  

郝朝运  刘鹏 《山地学报》2005,23(5):606-615

调查统计，磐安共有蕨类植物112种，隶属于60属、34科。地理成分分析表明，种的地理成分以东亚分布，特别是中国一日本分布为主，区系显示出较明显的亚热带一暖温带过渡的特征。同时从水平分布、垂直分布和生态分布三种分布型分析了磐安蕨类植物资源的分布规律，并根据其用途，划分为药用植物资源、食用植物资源、观赏植物资源等。在以上研究的基础上，提出了合理开发利用磐安蕨类植物资源的一些建议。  相似文献   

西部欠发达城市人口空间分布与演变     

陈浩  权东计  赵新正  何金璐 《世界地理研究》2019,28(4):105-114

探索西部欠发达城市人口空间格局及其演变特征，与东部发达城市人口分布形成对照，有利于认识城市人口分布规律，引导城市人口有序疏解。以西部欠发达城市兰州为例，对其乡镇街道尺度的常住人口数据进行空间化处理，在此基础上借鉴标准差椭圆分析思路，提出变形椭圆圈层法，并结合GIS空间分析和人口密度模型拟合等方法，多角度揭示2000-2010年兰州市人口空间分布格局及其演变特征。研究发现：兰州市人口分布呈现“带状集聚”特征和“圈层-分异”结构，形成“中心区和近郊区人口缓慢增长，外围区人口快速增长，远郊区人口明显减少”的格局；兰州市人口重心在10年间向东偏北方向移动，人口空间呈“西北-东南”分布格局，总体上表现出集聚态势，且10年间集聚态势有所强化；Smeed模型是刻画兰州市人口分布的最佳单中心模型，10年间人口分布的单中心趋势增强，人口多中心结构尚不成熟。  相似文献   

粤港澳大湾区人口老龄化时空特征及其经济效应     

李琼  李松林  张蓝澜  李昊  刘毅 《地理研究》2020,39(9):2130-2147

中国新时代“两个十五年”的现代化强国战略周期,恰恰是快速人口老龄化纵深发展期,人口年龄结构快速老龄化与经济社会之间的发展不平衡矛盾将日益严峻。本文利用广东省第四次、第五次、第六次人口普查资料、2015年广东省1%人口抽样调查资料、香港统计年刊和澳门统计年鉴数据,运用空间自相关分析法、柯布-道格拉斯生产函数和空间回归等方法,研究2000—2015年粤港澳大湾区人口老龄化的时空特征及其经济效应,结果表明：① 粤港澳大湾区人口老龄化进程慢于广东省,更慢于全国,但于2015年已进入老年型I期。② 粤港澳大湾区老龄化呈动态演变特征,空间上以香港和江门为起点,经西北向北扩散的“C”型分布模式,高收入城市以澳门和香港为起点向北扩散,最终形成中心-外围的空间分布格局。③ 粤港澳大湾区人口老龄化对经济增长具有负向影响,老龄人口增加1%,人均GDP降低3%。人均固定资本投入和人均人力资本投入有正的经济效应,人均人力资本投入带来的正向效应要大于人均固定资本投入。鉴于此,粤、港、澳三地应建立起协同治理模式,构建跨境的养老合作机制;促进产业结构升级,充分利用人力资本促进技术创新,并正确评估不同阶段人口老龄化对经济增长的影响,妥善处理好人口老龄化与经济之间的关系至关重要。  相似文献   

Computational model coupling mode II discrete fracture propagation with continuum damage zone evolution          下载免费PDF全文

Wencheng Jin  Hao Xu  Chloé Arson  Seth Busetti 《国际地质力学数值与分析法杂志》2017,41(2):223-250

We propose a numerical method that couples a cohesive zone model (CZM) and a finite element‐based continuum damage mechanics (CDM) model. The CZM represents a mode II macro‐fracture, and CDM finite elements (FE) represent the damage zone of the CZM. The coupled CZM/CDM model can capture the flow of energy that takes place between the bulk material that forms the matrix and the macroscopic fracture surfaces. The CDM model, which does not account for micro‐crack interaction, is calibrated against triaxial compression tests performed on Bakken shale, so as to reproduce the stress/strain curve before the failure peak. Based on a comparison with Kachanov's micro‐mechanical model, we confirm that the critical micro‐crack density value equal to 0.3 reflects the point at which crack interaction cannot be neglected. The CZM is assigned a pure mode II cohesive law that accounts for the dependence of the shear strength and energy release rate on confining pressure. The cohesive shear strength of the CZM is calibrated by calculating the shear stress necessary to reach a CDM damage of 0.3 during a direct shear test. We find that the shear cohesive strength of the CZM depends linearly on the confining pressure. Triaxial compression tests are simulated, in which the shale sample is modeled as an FE CDM continuum that contains a predefined thin cohesive zone representing the idealized shear fracture plane. The shear energy release rate of the CZM is fitted in order to match to the post‐peak stress/strain curves obtained during experimental tests performed on Bakken shale. We find that the energy release rate depends linearly on the shear cohesive strength. We then use the calibrated shale rheology to simulate the propagation of a meter‐scale mode II fracture. Under low confining pressure, the macroscopic crack (CZM) and its damaged zone (CDM) propagate simultaneously (i.e., during the same loading increments). Under high confining pressure, the fracture propagates in slip‐friction, that is, the debonding of the cohesive zone alternates with the propagation of continuum damage. The computational method is applicable to a range of geological injection problems including hydraulic fracturing and fluid storage and should be further enhanced by the addition of mode I and mixed mode (I+II+III) propagation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

海底光缆检测技术综述     

汤钟  邵浩  张斌 《数字海洋与水下攻防》2020,3(6):499-503

据统计，我国近岸70%以上海底光缆失效是遭受了渔船拖网作业或抛锚等活动的破坏。维护损坏的海底光缆，首先需要快速准确地定位光缆损坏段，同时获取光缆在海床上的布设状态以及布设区域的海床地形特征、地貌与底质特征等信息。在实际工作中，复杂的海床环境为海底光缆的检修及维护带来巨大的技术困难。围绕海底光缆巡检的技术需求，系统分析了常规海底光缆检测技术的特点，基于国内外水下无人机器人的发展现状，为提高海底光缆的检测效率、识别准确率和智能化水平提供了技术支撑。  相似文献