Major reactive species of ambient volatile organic compounds (VOCs) and their sources in Beijing

Volatile organic compounds (VOCs) are important precursors of atmospheric chemical processes. As a whole mixture, the ambient VOCs show very strong chemical reactivity. Based on OH radical loss rates in the air, the chemical reactivity of VOCs in Beijing was calculated. The results revealed that alkenes, accounting for only about 15% in the mixing ratio of VOCs, provide nearly 75% of the reactivity of ambient VOCs and the C4 to C5 alkenes were the major reactive species among the alkenes. The study of emission characteristics of various VOCs sources indicated that these alkenes are mainly from vehicle exhaust and gasoline evaporation. The reduction of alkene species in these two sources will be effective in photochemical pollution control in Beijing.     

Upper-Tropospheric Environment–Tropical Cyclone Interactions over the Western North Pacific: A Statistical Study

Based on 25-year(1987–2011) tropical cyclone(TC) best track data, a statistical study was carried out to investigate the basic features of upper-tropospheric TC–environment interactions over the western North Pacific. Interaction was defined as the absolute value of eddy momentum flux convergence(EFC) exceeding 10 m s~(-1)d~(-1). Based on this definition, it was found that 18% of all six-hourly TC samples experienced interaction. Extreme interaction cases showed that EFC can reach~120 m s~(-1)d~(-1) during the extratropical-cyclone(EC) stage, an order of magnitude larger than reported in previous studies.Composite analysis showed that positive interactions are characterized by a double-jet flow pattern, rather than the traditional trough pattern, because it is the jets that bring in large EFC from the upper-level environment to the TC center. The role of the outflow jet is also enhanced by relatively low inertial stability, as compared to the inflow jet. Among several environmental factors, it was found that extremely large EFC is usually accompanied by high inertial stability, low SST and strong vertical wind shear(VWS). Thus, the positive effect of EFC is cancelled by their negative effects. Only those samples during the EC stage, whose intensities were less dependent on VWS and the underlying SST, could survive in extremely large EFC environments, or even re-intensify. For classical TCs(not in the EC stage), it was found that environments with a moderate EFC value generally below ~25 m s~(-1)d~(-1) are more favorable for a TC's intensification than those with extremely large EFC.     

Vertical distributions of aerosol optical properties during haze and floating dust weather in Shanghai

A comparative study on the vertical distributions of aerosol optical properties during haze and floating dust weather in Shanghai was conducted based on the data obtained from a micro pulse lidar.There was a distinct difference in layer thickness and extinction coefficient under the two types of weather conditions.Aerosols were concentrated below 1 km and the aerosol extinction coefficients ranged from 0.25 to 1.50km^-1 on haze days.In contrast,aerosols with smaller extinction coefficients(0.20 0.35 km^-1) accumulated mainly from the surface to 2 km on floating dust days.The seasonal variations of extinction and aerosol optical depth（AOD） for both haze and floating dust cases were similar greatest in winter,smaller in spring,and smallest in autumn.More than 85%of the aerosols appeared in the atmosphere below 1 km during severe haze and floating dust weather.The diurnal variation of the extinction coefficient of haze exhibited a bimodal shape with two peaks in the morning or at noon,and at nightfall,respectively.The aerosol extinction coefficient gradually increased throughout the day during floating dust weather.Case studies showed that haze aerosols were generated from the surface and then lifted up,but floating dust aerosols were transported vertically from higher altitude to the surface.The AOD during floating dust weather was higher than that during haze.The boundary layer was more stable during haze than during floating dust weather.     

长江口海域营养盐的分布特征及其成因

以第二次全国污染基线调查资料为依据,分析了长江口海域营养盐分布特征及其成因。结果表明：本海域硝酸盐分布沿岸高,外海低;磷酸盐由外海向长洚口门呈舌形递增。长江口内营养盐含量明显偏高,这主要是长江口径流携带大量沿岸污水进入本违法乱纪 域所致。本海域富营养化程度较高,一旦外界条件成熟,极易发生赤潮。     

泰国的地震活动及地震工作的现状

应泰国气象厅的邀请，固定地震局派遣了由郑斯华、叶洪组成的中国国家地震局专家组，于１９９４年８月１７日至９月４日访问考察了泰国。访问期间，泰国地震专家们向专家组介绍了泰国的地震活动性和地震工作现状；专家组访问了泰国Ｃｈｕｌａｌｏｎｇｋｏｒｎ大学的土木工程系，了解了泰国地震工程研究的情况。本文介绍了泰国的地震构造和地震活动性以及泰国的地震工作现状等。     

岩土工程渗流参数反问题

系统介绍了目前国内外岩土工程渗流参数反问题研究的现状和进展，对参数辨识不适定性等问题做了讨论，并结合计算实践着重对几种典型求解方法的优缺点进行了比较和评述。对今后岩土工程渗流反问题研究提出了初浅的看法。     

2003年云南大姚6.2级、6.1级地震序列S波分裂研究c

在利用双差定位法对2003年7月21日、 10月16日云南大姚先后发生的6.2级、6.1级地震序列进行精定位的基础上，采用互相关系数法测量了两个地震序列的快波偏振方向和快慢波的延迟时间. 结果表明:① 两个地震序列的S波分裂现象较明显，除三台乡台以外，大部分台站记录到的地震快波平均偏振方向与区域最大水平主压应力方向基本一致，三台乡台的偏振方向出现两个峰值，平均偏振方向是N80deg;E，表现出与区域最大水平主压应力方向不一致的现象；② 序列延迟时间与震源深度之间没有明显规律性关系，但不同延迟时间范围内偏振方向表现出不同的规律；③ 两次地震序列S波分裂结果对比发现，6.2级地震序列快波的偏振方向明显较分散，快波平均偏振方向比6.1级地震序列大20deg;，而延迟时间方面二者相差不大；④S波分裂快波偏振方向所表现出的空间差异性，可能是由于在区域背景应力场的基础上叠加了两次6级主震产生的应力扰动引起的.      

Depth Distribution of Moho Discontinuity Beneath Beijing and Its Adjacent Area

Based on the method of "two-dimensional depth structure of the crust" proposed by Horiuchi et al., about 5000 arrival times of 303 local shallow earthquakes recorded by the Beijing Seismographic Network from 1990 ~ 1993 are used to investigate the depth distribution of Moho discontinuity beneath Beijing and its adjacent area. We simultaneously determined the hypocenter parameters and P- and S-wave station corrections. The data of the North China Network were also investigated. The results are as follows: (1) The depth distribution of Moho discontinuity becomes shallower from the northwest to the southeast, i.e., in Zhangjiakou area, the Moho discontinuity is located at a depth range from 40~42 km. In the Beijing area, it is 36~39 km. However, at the eastern and southeastern part of this area, it is only 28-30 km and 30~32 km, respectively. (2) Beneath the Tangshan area, there is another elliptic interface shallower than the Moho discontinuity. Separately, its major and minor axis is approximately along     

青藏高原500hpa暖性高压生成的热成风适应机制

本文利用热成风适应原理,采取分解分析法对青藏高原500hpa暖性高压的生成机制作了一些定性和定量的讨论。结果表明:在扰动的水平尺度大于热成风适应的特征尺度的条件下,当源地有明显的负值非热成风涡度出现时,流场将向温度场适应,而温度场由于高原的加热作用存在暖中心或暖脊,则适应的结果在高原大气500hpa形成暖性高压,并伴随高层辐合,低层辐散及下沉运动。     

遥感图象的马尔柯夫随机场模型的纹理识别方法

本文讨论了马尔柯夫随机场图象模型及邻域选择方法,提出了8邻域5特征参数的马尔柯夫随机场图象模型以及一套完整而有效的特征参数的估计算法,将这些特征参数变成可视图象从而实现了视算。对8类不同纹理的标准图象进行分类试验,其识别(分类)的平均正确率达97.57％。