平流层臭氧均相光化学系统的非线性特性——对Cl_x和NO_x排放强度变化的响应

建立了一个描述平流层臭氧均相光化学过程的箱模式,详细地讨论了人类活动所产生的污染物奇氯(Cl_x)和奇氮(NO_x)对光化系统状态的影响.结果发现,系统的解在状态—参数空间中构成一个‘尖拐’突变流型;当奇氯的排放强度从当前值提高约30%,或者奇氮的排放强度从当前值减少约30%时,将触发突变过程,臭氧将以不连续方式从高状态跳到低状态,浓度将减少约50倍.     

利用Cluster Ⅱ数据分析等离子体片区磁结构运动特性

利用Cluster Ⅱ 卫星上搭载的磁通门磁强计的观测数据,可以计算磁结构的运动速度.本文在GSM（Geocentric Solar Magnetospheric System,地心太阳磁层系）坐标系下处理了磁暴期间（2002年8月1日到2日）和磁场宁静期（2002年8月6日到7日）的等离子体片区的观测数据.通过分析磁结构速度的统计特性和频谱特性,得到以下结论：（1）磁结构运动速度呈现出不规则的摆动结构.（2）Vz的方差与Vy的方差近似相等,而远大于Vx的方差.这可能是由于“风袋效应”.（3）在黎明侧的等离子体片区, Vx和Vz的平均值约为0,但Vy的平均值的量级为-10 km/s.这可能是在等离子体片区Pc5压缩波造成的.（4）Vx, Vy, Vz的频谱在0033 min-1和0035 min-1之间都有一个峰值.     

东亚地区春季黑碳气溶胶源排放及其浓度分布

本研究收集整理了东亚地区一个黑碳气溶胶的排放源,并利用一个三维化学输送模式系统模拟研究了东亚地区春季黑碳气溶胶的输送和演变过程.黑碳气溶胶浓度的模拟值与地面观测站和观测船获取的监测值相比,模拟值与监测值具有良好的一致性,这表明本研究收集整理的黑碳气溶胶的排放量及其分布是基本合理的,模式系统较好地反映了黑碳气溶浓度的时空分布和变化趋势,再现了许多观测到的重要特征.模拟结果表明,东亚地区春季间隙性的长距离输送对于西北太平洋海域的黑碳气溶胶浓度分布具有非常重要的影响.     

特深地下管线的电磁场特征分析及探测研究

研究了管线的一系列电磁场特征,介绍了特深管线探测应用状况,通过实例分析了从1 m到21 m了不同埋深直线电流及强电流3~21 m情况下的电磁场Hx、Hz、ΔHx 〖WTBZ〗的归一化异常的分布特征 , 提出了对特深管线探测的对策,即频率、电流、远端接地等提高信噪比的技术对策,提出了确定地下金属管线平面位置、埋深的方法,利用水平磁场分量70%法确定管线深度的适用条件,分析了特深管线探测的干扰因素,广州市3个特深管线的探测成功实例,说明了方法的良好效果.     

北太平洋对人为二氧化碳吸收的数值模拟

采用一个开边界海盆尺度环流模式研究人为CO2在北太平洋的吸收和分布,并与闭边界模式的模拟结果进行了比较.模拟结果表明,西北太平洋和赤道东太平洋是两个重要的人为CO2汇.使用较大的等密度面扩散系数使得西北太平洋人为CO2通量增大,而赤道海区通量减小（RUN2）.与闭边界模式相比,开边界模式中该两个区域的人为CO2通量都增加了.1800～1997年间,北太平洋共吸收人为CO2 2375GtC(1Gt=1×1015 g, RUN1).副极地海区是人为CO2的一个重要输出区,能输出人为CO2吸收量的38％～54％,而20°N～30°N海区是人为CO2的一个重要贮存区,占整个北太平洋的24％.开边界对于10°N以南太平洋吸收和贮存人为CO2有很大影响.与基于观测资料的估计相比,虽然模式低估了西北太平洋的人为CO2的穿透,高估了东北太平洋的人为CO2的穿透,但总的说来,模式比较好地估计了人为CO2在北太平洋的贮存.     

气溶胶与东亚季风相互影响的研究进展

中国科学院地学部在第33次科学与技术前沿论坛对气溶胶与季风相互作用进行了深入讨论和评估.本文综述了在此次论坛上所报告的国际和中国气溶胶与东亚季风相互作用有关的研究进展.研究表明:(1)东亚季风能影响气溶胶的输送,特别是可以为由气溶胶引起的持续性强雾-霾天气过程的生成和发展提供适宜的大气环流背景场,东亚季风还在季节、年际、年代际等多时间尺度上影响气溶胶的输送和空间分布特征,季风区域的高水汽特征还可能影响气溶胶的光学及辐射效应;(2)已有证据表明气溶胶对于中国部分区域云的物理特征和降水有明显影响,在东南沿海地区,增加气溶胶的含量可能会抑制轻型和中度降水,对强降水可能有强化作用,但是此问题极为复杂,值得深入研究;(3)东亚夏季风活动的年际变化对中国区域气溶胶浓度和空间分布有明显影响,而且近几十年季风的减弱很可能利于区域气溶胶浓度增加.同时期,中国大气污染排放量的显著增加很可能减小了海陆温差和纬向差异,也不利于季风的增强.此外,文章对未来加强季风与气溶胶相互作用的研究给出了部分参考建议,还指出气溶胶对于东亚季风环流影响研究的不确定性.     

电离层电场的半年变化对F2区峰值电子浓度的影响

利用一个电离层理论模式,模拟了太阳活动低年、地磁宁静情况下,中低纬和赤道地区电离层F2区峰值电子浓度(NmF2)的半年变化规律,重点讨论了电离层电场对NmF2半年变化的影响.模拟结果表明,当输入的电场没有周年和半年变化时,磁赤道地区电离层NmF2本身就具有一定的半年变化特征,而在稍高的纬度上,NmF2半年变化的强度较弱.当输入的电场具有一定的半年变化时,电离层NmF2的半年变化强度有明显的改变,且这种改变随地方时和地磁纬度不同有明显的差别.在地磁赤道附近的电离层赤道槽地区,从上午到午夜的时间内,具有半年变化的电场对电离层NmF2半年变化的强度是减弱的作用,在其他的时间内,电场对电离层NmF2半年变化强度是加强的作用.而在稍高纬度的电离层驼峰地区,情况明显不同.从上午一直到翌日日出前,具有半年变化的电场对电离层NmF2半年变化的幅度都是加强的作用.在其他的时间内,电场对电离层NmF2半年变化的幅度是减弱的作用.同时,研究表明电离层电场对NmF2半年变化的作用和“赤道喷泉”现象强烈相关.     

MODIS卫星遥感气溶胶产品在北京市大气污染研究中的应用

利用NASA MODIS气溶胶光学厚度产品与北京市空气污染指数做了长期比较分析, 发现二者的直接对比相关较低; 在引入季节变化的气溶胶标高、考虑了气溶胶的垂直分布后, 二者的相关系数有所提高; 在考虑了湿度影响因子订正后, 二者的相关系数显著提高. 证实卫星遥感气溶胶光学厚度在经过垂直和湿度影响两方面的订正后, 可以作为监测颗粒物污染物地面分布的一个有效手段. 利用 MODIS资料对2004年10月一次污染个例的分析, 表明卫星遥感气溶胶可以细致描绘地面污染事件的形成过程, 发现区域尺度输送和地形因素对北京市空气质量具有显著影响. 高分辨率的反演结果给出北京城区及周边地区气溶胶光学厚度的年平均分布, 表明高分辨率卫星遥感可能在监测颗粒物排放源分布上具有潜在的应用价值.     

北京地区城市环境对云和降水影响的个例数值模拟研究

本文利用中尺度可分辨云模式(WRF,Weather Research and Forecasting)对2011年8月14日北京地区一次强降水过程进行了数值模拟和敏感性试验,研究了城市环境(包括城市气溶胶和城市地表)对北京地区云和降水的影响.研究结果表明:城市气溶胶污染增强和城市地表使得北京地区(城区和周边)降水量减少,对城区平均累积降水量的影响作用分别为-38.92%和-3.4%.降水系统向北京主城区移动过程中,城市气溶胶在城市环境影响降水过程中的作用逐渐减小为85.13%,城市地表的作用增加到14.87%.城市污染气溶胶增强,使得非降水性粒子增多,而降水性粒子减少,这不利于对流的发展增强,使得水汽的垂直输送减弱,导致区域降水量减小.城市地表对强对流的发展也表现为减弱作用,这使得水汽的垂直输送减小,区域降水量减小.     

单颗粒气溶胶质谱测定颗粒的有效密度

单颗粒质谱技术已被广泛应用于气溶胶粒径和质谱特征的测量,而对其他微物理性质的应用研究仍十分欠缺.基于单颗粒气溶胶质谱仪(SPAMS),本研究建立了两种测量气溶胶颗粒有效密度的方法:一是利用SPAMS测径系统记录的颗粒散射光信号与Mie理论模型计算得到的光散射截面呈正相关关系,通过最小二乘法拟合得到气溶胶颗粒的有效密度;二是通过差分电迁移粒径分析仪(DMA)-SPAMS仪器联用,同时测量气溶胶颗粒的电迁移和真空空气动力学粒径,从而计算不同粒径气溶胶颗粒的有效密度.通过标准小球,硫酸铵和硝酸钠的测试,证明本研究建立的两种方法均可应用于气溶胶有效密度的测量.该方法有效地拓展了SPAMS的分析功能,使之成为能够同时对颗粒物的粒径、化学成分、光散射和密度的综合测量技术,为深入认识气溶胶的环境和气候效应提供了强有力的分析手段.     

沙尘表面非均相化学过程的气候效应的初步模拟研究

建立了一个包含地表起尘机制的尘粒表面非均相化学模式, 并与区域气候——大气化学模式系统连接. 研究了沙尘气溶胶表面的非均相过程对大气中一些重要微量成分浓度的影响及其所产生的气候效应. 结果表明,非均相过程使得二氧化硫和臭氧的浓度降低,硫酸盐浓度增加,年平均硫酸盐积分浓度增加26mg/m2;在部分地区非均相过程使二氧化氮浓度降低,而在另外一些地区,则使二氧化氮浓度增加. 1,4,7,10月四个月硫酸盐浓度增加造成的辐射强迫最大值分别为-0.24,-1.0,-2.0,-0.6 W/m2,全区域年平均辐射强迫为-0.033 W/m2. 四个月最大降温分别可达0.16,0.35,0.5,0.48K,年平均降温0.021K. 非均相过程对月总降水亦有明显的影响.     

Probability density functions for advective–reactive transport in radial flow

We study transport of a reactive solute in a chemically heterogeneous porous medium whose chemical properties are uncertain. The dissolved substance undergoes a heterogeneous chemical reaction with a solid phase in the presence of advection caused by extraction/injection from a point source. We present semi-analytical solutions for the probability density function of the solute concentration, which allows us to quantify predictive uncertainty associated with uncertain reaction rate constants for both linear and nonlinear reactions. This enables one to compute probabilities of rare events, which are required for quantitative risk analyses.     

Detailed PSC formation in a two-dimensional chemical transport model of the stratosphere

A new two-dimensional zonal model of the stratosphere, based on a formulation in an isentropic framework, with complete chemistry has been coupled with a high resolution detailed microphysical model for polar stratospheric clouds (PSCs). The 2D model chemistry includes all presently known heterogeneous processes on sulfate aerosols and PSCs. The coupling of these two models, with inherently different time scales, is discussed. It is demonstrated that in order to obtain a realistic interrelationship between NO_y and N₂O an accurate simulation of the sedimentation by PSC particles is necessary. A good agreement of model PSC presence and observations is found for the Antarctic polar winter without the need to impose additional artificial temperature variations in the model. The calculated occurrence of polar stratospheric clouds and resulting heterogeneous chemistry during the Antarctic winter are discussed. Sensitivity of the polar stratospheric chemical composition and cloud formation for different perturbations is investigated by studying the effects of transport across the polar vortex boundary and heterogeneous processing by an enhanced sulfate aerosol load. The importance of including sedimentation for all cases is also discussed.     

The heterogeneous oxidation of SO2 on aerosol surface

A heterogeneous chemical model is developed by coupling aerosol, gas-phase and liquid-phase chemical model. SO₂ oxidation rates on the aerosol surface are calculated and the influence of some factors is discussed. Model simulations indicate that SO₂ heterogeneous oxidation rates are sensitive to the mass concentration and chemical composition of aerosols, relative humidity, initial values of SO₂ and H₂O₂. The heterogeneous chemical model is coupled with a Eulerian deposition model. Model results show that oxidation of SO₂ on the aerosol surface is found to reduce SO₂ levels by 5%–33%, to increase SO ₄ ^2- - concentrations by 8%–50% in the surface layer. Project supported by the National “85-912” Key Science and Technology Project.     

Analysis of biodegradation in a 3-D heterogeneous porous medium using nonlinear stochastic finite element method

Probabilistic analysis by Monte Carlo Simulation method (MCSM) is a computationally prohibitive task for a reactive solute transport involving coupled PDEs with nonlinear source/sink terms in 3-D heterogeneous porous media. The perturbation based stochastic finite element method (SFEM) is an attractive alternative method to MCSM as it is computationally efficient and accurate. In the present study SFEM is developed for solving nonlinear reactive solute transport problem in a 3-D heterogeneous medium. Here the solution of the biodegradation problem involving a single solute by a single class of microorganisms coupled with dynamic microbial growth is attempted using this method. The SFEM here produces a second-order accurate solution for the mean and a first-order accurate solution for the standard deviation of concentrations. In this study both the physical parameters (hydraulic conductivity, porosity, dispersivity and diffusion coefficient) and the biological parameters (maximum substrate utilization rate and the coefficient of cell decay) are considered as spatially varying random fields. A comparison between the MCSM and SFEM for the mean and standard deviation of concentration is made for 1-D and 3-D problem. The effects of heterogeneity on the degradation of substrate and growth of biomass concentrations for a range of variances of input parameters are discussed for both 1-D and 3-D problems.     

Development of a chemistry module for GCMs: first results of a multiannual integration

The comprehensive chemistry module CHEM has been developed for application in general circulation models (GCMs) describing tropospheric and stratospheric chemistry, including photochemical reactions and heterogeneous reactions on sulphate aerosols and polar stratospheric clouds. It has been coupled to the spectral atmospheric GCM ECHAM3. The model configuration used in the current study has been run in an –off-line mode, i.e. the calculated chemical species do not affect the radiative forcing of the dynamic fields. First results of a 15-year model integration indicate that the model ECHAM3/CHEM runs are numerically efficient and stable, i.e. that no model drift can be detected in dynamic and chemical parameters. The model reproduces the main features regarding ozone, in particular intra- and interannual variability. The ozone columns are somewhat higher than observed (approximately 10%), while the amplitude of the annual cycle is in agreement with observations. A comparison with HALOE data reveals, however, a serious model deficiency regarding lower-stratosphere dynamics at high latitudes. Contrary to what is concluded by observations, the lower stratosphere is characterized by slight upward motions in the polar regions, so that some of the mentioned good agreements must be considered as fortuitous. Nevertheless, ECHAM3/CHEM well describes the chemical processes leading to ozone reduction. It has been shown that the mean fraction of the northern hemisphere, which is covered by polar stratospheric clouds (PSCs) as well as the temporal appearance of PSCs in the model, is in fair agreement with observations. The model results show an activation of chlorine inside the polar vortex which is stronger in the southern than in the northern winter hemisphere, yielding an ozone hole over the Antarctic; this hole, however, is also caused to a substantial degree by the dynamics. Interhemispheric differences concerning reformation of chlorine reservoir species HCl and ClONO₂ in spring have also been well reproduced by the model.     

Potential effects on ozone of future supersonic aircraft/2D simulation

In a previous work, the stratospheric effect of a future supersonic aircraft fleet on ozone has been simulated, by using a photochemical diffusive 1D model and a 2D photochemical, radiative dynamical model. The fleet scenario was defined by Aerospatiale and Snecma for a current technology Mach-2 aircraft; the models were limited to simplified homogeneous phase reactions. The results indicated a global ozone decrease of about 1.5% in steady-state conditions. Now the 2D model has been upgraded and includes the classical heterogeneous reactions with Polar Strato- spheric Clouds (PSC) and aerosol. It also takes into account the natural or anthopogenic evolution of the background atmosphere. The scenario has been optimized to meet more realistic conditions. Thus, new results are presented. The main conclusion concerning the calculated impact of a realistic fleet for the next 20–50 years is still weaker than in the previous work: the decrease for the total ozone would always be lower than 0.3%. These results are commented, with the help of a parametric study, pointing out the importance of the background atmosphere and especially the total chlorine loading and the aerosol surface area.     

Balloon observations of organic and inorganic chlorine in the stratosphere: the role of HClO4 production on sulfate aerosols

Simultaneous observations of stratospheric organic and inorganic chlorine were made in September 1993 out of Fort Sumner, New Mexico, using JPL balloon-borne MkIV interferometer. Between 15 and 20 km, a significant fraction (20-60%) of the inorganic chlorine could not be accounted for by the sum of measured HCl, ClONO2, and HOCl. Laboratory measurements of the reaction of ClO radicals on sulfuric acid solutions have indicated that, along with HCl, small amounts of perchloric acid, HClO4, were formed. Very little is known about the fate of HClO4 in the stratosphere and we use a photochemical box model to determine the impact of this new species on the partitioning of inorganic chlorine in the stratosphere. Assuming that HClO4 is photochemically stable, it is shown that in the enhanced aerosol loading conditions resulting from Mt. Pinatubo's eruption, HClO4 could represent a significant reservoir of chlorine in the lower stratosphere, sequestering up to 0.2 ppbv (or 50%) of the total inorganic chlorine at 16 km. The occurrence of this new species could bring to closure the inorganic chlorine budget deficiency made apparent by recent ER-2 aircraft in situ measurements of HCl.     

Nitrogen in fluids effecting retrogression of granulite facies gneisses: a debatable mantle connection

The abundance patterns of nitrogen, and chlorine in retrogressed granulite facies gneisses from southern East Greenland exhibit strong enrichment in the vicinity of small-scale shear zones. Sulfur in the shear zones occurs at the same concentration levels as in the adjacent country rock, but is depleted in the transition zone between shear zone and country rock. Within the shear zone sulfur occurs as sulfate, whereas in the country rock granulites it occurs as sulfide. Recrystallization of rock in the shear zone to scapolite-bearing, hornblende-absent assemblages, along with changes in the major element chemistry, demonstrates that these zones define migration pathways of chemically reactive fluids. Consideration of the computed fluid compositions, and of the mass ratios of chlorine/sulfur and nitrogen/sulfur demonstrate that the fluid equilibrated with continental crust prior to its passage through gneisses in the study area. Previous suggestions have been made that the mantle may act as a source region for nitrogen-rich fluids. However, equilibration of these S-, N- and Cl-rich fluids with crustal material precludes the use of element abundances to identify a mantle signature; the bulk of these fluid constituents must be considered crustal derived.     

A general mixing equation with applications to Icelandic basalts

The mixing equation applied by Vollmer [1] to Pb and Sr isotope ratios is shown to be a general equation applicable to consideration of element and isotope ratios. The mixing equation is hyperbolic and has the form:Ax + Bxy + Cy + D = 0where the coefficients are dependent on the type of plot considered: i.e. ratio-ratio, ratio-element, or element-element. Careful use of this equation permits testing whether mixing is a viable process, places constraints on end member compositions, allows distinction between mixing of sources and mixing of magmas, and should allow distinction between recent mixing and long-term evolution of sources.The available chemical data for postglacial basalts from Iceland and along the Reykjanes Ridge are not consistent with either mixing of magmas or simple mixing of an enriched ocean island source with a depleted ocean ridge source. If the available analyses for basalts are representative of the source regions, the data are consistent with at least two models neither of which can be properly tested with the available data.(1) There are two separate mixing trends: one beneath Iceland with the alkali basalt source and a depleted Iceland source as end members; the second along the Reykjanes Ridge with a heterogeneous ocean ridge basalt source and a source similar to that for intermediate basalts on Iceland as end members. The depleted Iceland source and the depleted ocean ridge source are not the same.(2) The chemistry of the basalts is not determined by mixing. Instead the basalts are derived from a multiplicity of sources with a similar history which have been isolated for hundreds of millions of years.