差分反射率ZDR和反射率Ze测雨精度的对比分析

本文根据大量不同类型降雨的雨滴谱资料，分析了两种雷达测雨与滴尺度分布的关系，模拟计算了双线偏振雷达可测到的(R/ZH)-ZDR和常规天气雷达可测到的Z-R经验关系和它们在测量降雨率精度的对比分析。表明差分反射率ZDR对改进雷达测雨的精度有着明显的优势。     

Correcting Distortions in Measurements of Atmospheric Pressure Fluctuations

Although recognized as important, measurements of turbulent atmospheric pressure are considered difficult and are conducted infrequently. Here we discuss the essential elements in the design of an instrument for measuring turbulent fluctuations of atmospheric pressure. Our analysis of the instrument’s dynamics is focused on the signal distortions resulting from a pneumatic filter, a necessary element in the instrument’s design. Such distortions substantially affect the observed spectral scaling of the pressure field as well as other quantities of physical interest, such as pressure-velocity 〈p, v〉 and pressure-wave 〈p, η〉 covariances. We propose a computationally efficient discrete-time signal processing method for complete compensation of pneumatic filter distortions and review the criteria for selecting the instrument parameters (sampling frequency and time constant), so that digital filter distortions, precision degradation, clipping, and over-damping, are simultaneously avoided. This correction method must be an inherent part of the instrument’s design.     

Long-Term Measurements of Light Hydrocarbons (C2–C5) at Schauinsland (Black Forest)

Long-term measurements of light hydrocarbons(C₂–C₅ HCs) were performed in the courseof the EUROTRAC sub-project TOR (Tropospheric Ozone Research) in thesouthern part of the Black Forest in southwest Germany. The measurementscover a time period of five years (January 1989–January 1994) and theair samples were analyzed onsite by an automated GC-system. Pronouncedannual cycles with maxima in late winter and minima in late summer wereobserved in the case of the slowly reacting hydrocarbons ethane, propane andacetylene, reflecting the fact that the seasonal variation of these speciesis photochemically driven. For the shorter lived compounds the seasonalvariations are considerably weaker, connected with a stronger scatter of theindividual measurements, which is caused by different distances to theirmain sources for different wind vectors as well as by varying sourcestrengths. From a detailed characterization of the hydrocarbon patterns theinfluence of two different sources could be distinguished. An extrapolationto photochemical age of zero and completion of our data with those from aspeciated VOC inventory yields an estimated [VOC]/NO_x sourceratio for Schauinsland of 5 [ppbC/ppb]. Comparable[VOC]/NO_x ratios are observed in automobile exhaust gasesunder low speed conditions, which points to the important role of trafficunder conditions, when freshly polluted air masses from a near-by city areadvected to the site. From an investigation of the photochemical age of theadvected air masses it becomes clear that there must exist biogenic sourcesof light olefins in the vicinity of the observatory during the vegetationperiod. For propene and the butenes we are able to estimate a lower limit oftheir contributions in terms of reactivity to the total reactivity( [HC](i) k_OH(i),i=C₂-C₅) of the measured hydrocarbons. Forlowest pollution levels in summer (acetylene <300 ppt, about 40%of the summer values) this source is found to be responsible for15–20% of the total C₂–C₅reactivity observed at Schauinsland. On the average, this source accountsfor 5–10% of the total C₂–C₅reactivity.     

地质环境的地球化学研究——贺"环境地质学的出现"发表30周年暨中国科学院地球化学研究所环境地球化学国家重点实验室成立10周年

1972年刘东生院土撰文发表了“环境地质学的出现”。中国科学院地球化学研究所环境地球化学国家重点实验室于1992年正式成立,刘东生院士的环境地质学学术观点聚焦于：环境地质学发展的动力源于社会需要,地球环境系统的整体性及其与人类关系的相互依存性。30年来,地质环境的地球化学研究以区域环境质量和全球环境变化两大科学问题作了基本目标,经历了调查评价,区域综合和界面机理3个发展阶段,研究重点是典型区域环境演化的发生学原理,谱系特征以及健康和生态效应,云贵高原地质环境的特殊性显示出青藏隆起对周边现代环境的影响。环境地质学以“地质学与人类”为宗旨,将在21世纪为人类谋求更多的福利。     

EPR and SQUID magnetometry study of Cu2FeSnS4 (stannite) and Cu2ZnSnS4 (kesterite)

An EPR and SQUID magnetometry study of Cu₂FeSnS₄ (stannite) and Cu₂ZnSnS₄ (kesterite) has been performed in order to gain a deeper insight into the crystal chemistry of these minerals, in which the mixed character of bonds lends uncertainty to the determination of the metal valence states. EPR investigations were performed down to almost liquid nitrogen temperature on both natural and synthetic samples of stannite and kesterite. The interpretation of their parameters (g- and T-tensors) was refined by computer simulation. The main feature of all the spectra is the unstructured signal centered at about 0.310 T due to the presence of Cu(II). The absence of structure in the signal is due to spin-spin exchange interaction between Cu(II) and Fe(II), pointing to a diluted distribution of Cu(II). The temperature dependence of the Cu(II) signal can be related to a topological variation of the first-neighbors coordination. The SQUID measurements, while allowing a more precise interpretation of the EPR data, led to a full characterization of magnetic behavior of stannite and kesterite down to liquid helium temperature, evidencing antiferromagnetic interactions between the Fe(II) ions in all samples but in synthetic kesterite. From the EPR and SQUID experimental data no evidence was provided for the existence of two different structures for stannite and kesterite. Received: 2 August 1999 / Accepted: 7 January 2000     

祁连山冷锋过程中积层混合云微物理特征飞机观测研究

利用高性能空中国王飞机搭载的DMT(Droplet Measurement Technologies)探测系统,分析2020年6月15—16日祁连山地区两次冷锋过程前后积层混合云的宏微观特征。结果表明:冷锋前CIP(Cloud Imaging Probe)粒子平均浓度在10¹~10²L^-1,PIP(Precipitation Imaging Probe)粒子浓度在10² L^-1;CIP粒子数浓度随高度逐渐上升,降水粒子在7 300 m时浓度达到峰值后下降;平均粒子谱拓宽速率为3.5 mm·km^-1,随着高度的下降而降低。冷锋前存在对流泡区域,对流泡内粒子浓度均高出对流泡外,粒子谱拓宽速率高出层云一倍。冷锋后大CIP粒子粒子浓度为10² L^-1,降水粒子浓度为10⁰~10² L^-1,粒子谱拓宽速率为1.5 mm·km^-1,较冷锋前粒子谱拓宽速率小1.7倍。锋前后粒子均呈现多峰型;锋前积层混合云云中对流泡内外谱型一致,云顶处对流泡内外峰值粒径不同。锋前云粒子形状为聚合状、枝状、柱状和不规则状,以聚合状为主;云内冰晶以凇附和聚合增长为主;对流泡内外在粒子形态上没有明显差异。锋后粒子形状以不规则粒子为主,云粒子增长形式以聚合增长为主,并伴有上层云向下层播撒大云粒子的现象。     

植被冠层日光诱导叶绿素荧光塔基自动观测方法及系统介绍

植物光合作用所提供的物质和能量是人类赖以生存的关键因素,而日光诱导叶绿素荧光SIF(Sun-Induced chlorophyll Fluorescence)是植物光合作用的副产品,与光合作用关系密切,深入研究SIF将对于更加深入理解光合作用机制有着重要的意义.目前,近地面植被冠层SIF遥感观测发展迅速,但不同SIF观...