云南省温度和气溶胶对微雨影响的初步分析     

胡安德 《云南地理环境研究》2012,24(4):82-86

近40年云南省平均总微雨量占年总雨量比例﹑年平均总微雨日占年总雨日比例均呈下降趋势,并有从北向南逐渐减少的分布规律;近40年云南省年平均能见度也呈下降趋势,其趋势分布同微雨降水趋势分布比较一致;微雨降水的变化同干燥晴天能见度存在正的相关关系,其中云南省东部地区相关显著;而温度与微雨降水存在负相关;云南省气溶胶在一定程度上抑制微雨降水,云南东部气溶胶对微雨的影响比较显著。  相似文献   

A geographic perspective on intra-urban racial/ethnic diversity, segregation, and clustering in Knoxville, Tennessee: 1990-2000     

Madhuri Sharma 《Applied geography (Sevenoaks, England)》2012,32(2):310-323

Racial/ethnic diversity in the United States has increased significantly in recent decades, with minority groups now accounting for almost one-third of the total population. At the same time, growing diversity has spread into rural and non-metropolitan areas. Research suggests that changing diversity in the ‘New South’ has seen growth of non-Black communities. The question, however, is the degree to which increasing diversity equates with increasing intermixing or, alternatively, whether racial/ethnic clusters retain their prominence. This paper examines the geographic manifestations of growing racial/ethnic diversity within intra-urban context, using census-tracts as scale of analysis in the metropolitan statistical area (MSA) of Knoxville in Tennessee. The statistics used for analyzing intra-urban variations include Diversity Score, Theil Entropy Index, and Location Quotient. Tract and Block-group data for White, Black, American Indian, Asian, All Others and Hispanic are used for computing these indices. This paper concludes that diversity has increased during 1990-2000, and has dispersed into suburban counties. However, segregation and clustering for certain minority groups has also increased, in particular African-Americans still remain the most segregated and most clustered community confined to specific geographic locations. This research holds significance as local economic development patterns are very much guided by the geographic variability of human and social capital. Applied research can suggest avenues for growth and can help rebuild local communities. This paper will also contribute to literature focusing on methodological challenges in measuring diversity and its geographic manifestations.  相似文献   

Knowledge gathering and communication on biodiversity: Developing the Norwegian Nature Index     

《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(5):300-308

The authors reflect on knowledge-generating and communication processes involved in the recently developed Norwegian Nature Index, particularly the communication process among experts involved in providing the required biodiversity knowledge. Eliciting a comprehensive overview of biodiversity is a complex process involving choices of approaches and methods in order to reach a common understanding of uncertainties and values as a basis for quantification. Part of the complexity is the establishment of dialogue between experts from research institutions with different research traditions and approaches. The authors discuss how the index was developed through communication processes, challenging involved experts to provide not only biodiversity data for the current situation, but also forecasts of future trends, assessments of uncertainty, and evaluations of the urgency of biodiversity loss and possibility of implementing policy and management measures. The Nature Index framework has potential for informing the biodiversity policy debate by involving stakeholders beyond the science-policy community and enhancing deliberations about biodiversity policy in a wider context of sustainable development. As a policy tool, the Nature Index may develop through a process of practical application, which in turn may have an impact on the selection of narratives, definition of management targets, and technical concepts such as reference states.  相似文献   

华北地区典型污染天大气气溶胶飞机探测个例分析   总被引：5，自引：0，他引：5  

张瑜  银燕  石立新  段英  吴志会 《高原气象》2012,31(5):1432-1438

利用2005年10月17日华北地区一次典型污染天气条件下的飞机探测资料,对石家庄和邯郸气溶胶的微物理特征进行了对比分析,初步讨论了该天气条件下大气气溶胶污染的微观特征和可能原因。结果表明,观测当天石家庄和邯郸地区的气溶胶粒子浓度很高,边界层内气溶胶平均数浓度为103cm-3量级,最高值出现在近地面附近,达到104cm-3量级;边界层以上的数浓度基本都在103cm-3量级,属于空气污染比较严重的一次过程。造成污染的原因是该日晴天风小,大气湍流较弱,不利于污染物扩散和稀释。基于美国国家海洋和大气局(NOAA)后向轨迹模式(HYSPLIT4)对颗粒物进行溯源和追踪分析,发现造成气溶胶浓度较高的气块传输路径主要为西北和偏西路径,境外源主要来自蒙古国,境内源主要来自我国西部,途经甘肃、宁夏、陕西及山西后进入河北。  相似文献   

大同地区典型沙尘天气过程近地层气象要素演变特征的对比分析     

郝玉峰  施占军  王淑凤 《山西气象》2012,(1):25-28

利用2009年3月-2010年3月大同国家基准气候站20m气象梯度塔的风向、风速、气温、相对湿度的观测资料及PM10质量浓度数据、气溶胶散射系数数据,分析大同地区典型沙尘天气过程近地层气象要素演变特征。结果表明,风速在沙尘暴、扬沙的发生、发展过程中均较大,浮尘较小。气温在沙尘暴期间受冷空气的影响迅速减小,而在扬沙和浮尘天气条件下温度的变化主要取决于长短波辐射的强弱和沙尘气溶胶的辐射强迫。相对湿度在沙尘暴期间基本上呈递增态势,结束后比发生前相对湿度增大,在扬沙和浮尘天气条件下,相对湿度与温度完全呈现出反相关关系,且相对湿度均较小。PM10质量浓度在沙尘暴、扬沙、浮尘天气条件下依次递减。沙尘暴期间气溶胶散射系数明显增大。  相似文献   

江苏省连阴雨过程时空分布特征分析     

项瑛  程婷  王可法  李进喜  唐红昇 《气象科学》2012,32(S1):36-39

通过综合各地连阴雨指标因子, 确定了江苏省连阴雨过程的标准, 根据指标体系, 对其时空分布特征进行了分析, 得出江苏省年均连阴雨次数为12.3次, 连阴雨的空间分布存在着明显的北少南多的特征, 可见沿江苏南地区为连阴雨的频发地区。其中从对农作物危害程度来看, 主要是春季连阴雨(3—5月)和秋季连阴雨(9—11月)影响较大, 这两个时段连阴雨过程发生次数较多, 分别为年均3.1和2.7次, 其中春季3月和秋季9月的连阴雨出现次数最多。为了进一步定量评估连阴雨的强度, 我们设计了连阴雨强度指数模型, 对强度指数M_LYY进行了分级, 实施了对连阴雨强度的进一步把握, 更好地为决策部门提供了服务。  相似文献   

边界层温度廓线遥感反演的本地化改进研究     

张杰  张强  李俊 《气象学报》2010,68(2):207-216

采用MODIS资料和美国发展的MODIS大气温、湿度廓线统计反演算法,估算大气温度、湿度廓线作为初始场,应用101层快速透过率模式(PFAAST)估算了大气透过率,并采用Newton非线性迭代算法反演中国西北荒漠戈壁地区大气温度廓线。结果表明:该方法对边界层高度及以上部分的大气温度反演得比较好,误差基本都在2 K范围内,边界层范围内的温度反演误差较大,反演误差与气溶胶光学厚度增量和地表温度估算误差呈显著正相关关系,与大气水汽混合比的关系较差。文中从敏感性试验和理论分析角度阐述了地表温度和气溶胶光学厚度估算误差对大气温度反演误差的影响,发现不同光谱波段的地表温度权重均随地表温度的增加有不同程度增加,地表温度反演误差增加将增加地表温度权重,提高地表温度估算误差有助于提高地表温度权重的精度;荒漠戈壁地区大气边界层中气溶胶浓度较高,光学厚度较大,使边界层大气透过率降低,进而降低卫星红外遥感波段的地表温度权重和空气温度权重。由于该模式没有很好地考虑边界层中沙尘气溶胶的影响,使卫星反演的大气透过率偏高,以至于高估地表温度权重和大气温度权重,使得反演的表面温度和空气温度偏低。该研究结合太阳光度计获得的光学厚度资料,采用统计方法对气溶胶效应引起的大气透过率误差和表面温度估算误差进行校正,并对物理算法进行本地化改进,实现了边界层温度廓线的反演。  相似文献   

纬向平均的风向改变指数与季节转换     

朱敏  张铭  徐建霞 《热带气象学报》2010,26(1):86-92

通过定义一个能客观定量描述大气环流四维时空变化的风向改变指数WI,用以研究大气环流的时空演变规律和季节转换。在对纬向平均的WI做了经验正交函数(EOF)分析后,得到了其前四个模态。第一模态揭示的是全年平均的WI空间分布的基态。第二模态反映的是WI场的偏差中呈现准调和变化的部分,热带、副热带、温寒带季风区在该模态中均有明显体现。第三模态反映的是WI场的偏差中呈现非调和变化的部分,该部分揭示了因南北半球海陆分布的差异和因大气、海洋流体的非线性效应,其所造成的从春到秋与从秋到春的季节变化的不对称性以及平流层的二月突变现象。第四模态反映的是全球各层盛行风反向区域从春到夏的北进和从夏到秋南撤的现象。  相似文献   

On the formation and growth of atmospheric nanoparticles   总被引：2，自引：0，他引：2  

Markku Kulmala  Veli-Matti Kerminen 《Atmospheric Research》2008,90(2-4):132-ICNAA07

In this paper we summarize recent experimental, theoretical and observational results on the formation and growth of atmospheric nanoparticles. During the last years significant progress has occurred to explain atmospheric nucleation and initial steps of the growth. Due to climatic and health effects of fine and ultrafine particles the formation and growth of new aerosol particles is of growing interest. The question “How and under which conditions does the formation of new atmospheric aerosol particles take place?” has exercised the minds of scientists since the time of John Aitken, who in the late 1880s built the first apparatus to measure the number of dust and fog particles. However, only during the last 15–20 years has the measurement technology developed to such a level that size distributions of nanometer-size particles and concentrations of gases participating in particle formation can be measured in the atmosphere. Also from a theoretical point of view atmospheric nucleation mechanisms have not been resolved: several mechanisms such as ion-induced (or ion mediated) nucleation, ternary and kinetic (barrier-less) nucleation have been suggested. In the most recent theory, the activation of existing neutral and/or ion clusters has been suggested.  相似文献   

Composition and major sources of organic compounds in urban aerosols     

Xinhui Bi  Bernd R.T. Simoneit  Guoying Sheng  Shexia Ma  Jiamo Fu   《Atmospheric Research》2008,88(3-4):256-265

Total suspended particles (TSP), collected during June 2002 to July 2003 in Guangzhou, a typical economically developed city in South China, were analyzed for the organic compound compositions using gas chromatography–mass spectrometry (GC/MS). Over 140 organic compounds were detected in the aerosols and grouped into different classes including n-alkanes, hopanoids, polycyclic aromatic hydrocarbons, alkanols, fatty acids, dicarboxylic acids excluding oxalic acid, polyols/polyacids, lignin products, phytosterols, phthalates and water-soluble sugars. The total amounts of the identified organic compounds including unresolved complex mixture (UCM) ranged from 3112 ng/m³ in spring to 5116 ng/m³ in winter, comprising on seasonal average 2.8% of TSP. Primary organic compounds peaked in winter although there are no heating systems burning fuels in Guangzhou. The highest saccharide levels occurred in fall due to agricultural activities. This study demonstrated that utilization of fossil fuels, biomass burning, soil resuspension and plastic/refuse burning are the major contributors to the identified organic compounds in the urban atmosphere of South China.  相似文献