Hardening of Titan's aerosols by their charging

Titan's haze consists of long chain polymers of pure and N-mixed hydrocarbons (Coustenis et al., 1989, Icarus 80, 54-76, 1991, Icarus 89, 152-167). These polymers have regularly alternating (i.e., conjugated) double/single and triple/single bonds, which open either spontaneously (free aging) or under the action of some external factors (forced aging), the latter being very diverse, e.g., charging, photolysis, radiolysis, thermolysis, chemical effect of environment, etc. An essential of free aging was examined previously (Dimitrov and Bar-Nun, 2002, Icarus 156, 530-538). The main distinction between free and any forced aging is that both of them possess the same thermodynamics while different kinetics, the forced aging in any case being faster, proceeding in different pathways than the free aging. The more extensive is the list of the external effects and the more intensive they are, the faster and more variably the forced aging proceeds. In this paper we quantified the kinetics of forced aging, considering charging of Titan's aerosol population. It was found that forced aging proceeds approximately hundred times faster as compared to the free aging. Various physico-chemical properties of Titan's aerosol material, including coagulation coefficients, depending on particle size and medium conditions, were defined. The comparison of the aging rate, rate of sedimentation and rate of the particle increase proves that Titan's aerosol domain can be subdivided conditionally into two big subdomains. The upper one contains minor portion (<5%) of the total aerosol bulk, unannealed aerosol particles being fine and sticky. The lower subdomain contains the major portion (>95%) of aerosol bulk, which is completely aged, coarsely dispersed particles. We established the border between these subdomains at the altitude Z∼620 km.     

Global climatic change – the latest scientific understanding

IPCCs statement in its 1995 report (IPCC 1996) that a human influence was discernible in global climate has been widely quoted but often misunderstood. The character of the evidence underpinning this detection statement is explained so that its strengths and weaknesses can be better understood and the subtleties of its message better appreciated. To demonstrate the close linkage between the government-approved summary and the underlying chapters of the IPCC report the detailed evolution of the detection statement from first draft through to the form finally approved by the IPCC is described.     

EXPERIMENTAL STUDY ON EFFECTS OF HUMIDITY AND CHEMICAL COMPOSITION UPON IMAGINARY PART OF REFRACTIVE INDEX OF AEROSOL PARTICLES*

Experimental study is made of the relationship between the imaginary part of refractive index (IRI) of atmospheric aerosol particles and relative humidity,and between IRI and chemical element through the assay of chemical constituents of the particles.Evidence suggests that atmospheric humidity and aerosols' chemical ingredients have great effects on the IRI's and they should thus be considered in the research of the radiation properties of the particles in the atmosphere.     

Biomass Burning in Southern Africa: Individual Particle Characterization of Atmospheric Aerosols and Savanna Fire Samples

Ambient atmospheric aerosols and savanna fireparticulate emission samples from southern Africa werecharacterised in terms of particle classes and theirnumber abundance by electron probe X-ray microanalysis(EPXMA). About ten particle classes were identifiedfor each sample. The major classes werealuminosilicates and sea salts for ambient coarse(2–10 m equivalent aerodynamic diameter (EAD))samples, and K-S and S-only particles for ambient fine(<2 m EAD) samples. The K-S particles are oneof the major products of biomass burning. The EPXMAresults were found to be consistent with the resultsfrom bulk analyses on a sample by sample basis. Forsavanna fire fine samples, quantitative EPXMA revealedthat many particles had a composition of simple saltssuch as KCl. Some particles had a deviatingcomposition in the sense that more ionic species wereinvolved in sustaining the balance between cations andanions, and they were composite or mixed salts.Because of extensive processing during the atmospherictransport, the composition of the K-S particles in theambient samples was different from K₂SO₄,and such particles were enriched with S. The finepyrogenic KCl particles and the fine sea-saltparticles were much depleted in chlorine.     

中国区域气溶胶对东亚夏季风的可能影响(Ⅱ)：黑碳气溶胶及其与硫酸盐气溶胶的综合影响

 利用NCAR的新一代GCM CAM3.0模式耦合一个气溶胶同化系统,研究了中国区域黑碳气溶胶的直接气候效应。结果显示,中国区域黑碳气溶胶引起全球平均辐射强迫为0.13 W/m2,导致除了青藏高原和广西以外的中国大部分地区降温,其中东北、四川和内蒙古中北部降温最显著。由此造成海陆温差缩小,气压差降低,从而总体上使东亚夏季风减弱。但与硫酸盐气溶胶的影响相比,黑碳气溶胶使季风减弱的程度较小,长江中下游地区的降水有所增加。黑碳气溶胶加强了中国东南部地区的对流活动,这与硫酸盐气溶胶的作用相反。同时,探讨了中国区域硫酸盐和黑碳气溶胶的综合直接气候效应。结果表明,硫酸盐和黑碳气溶胶的综合作用与仅有硫酸盐气溶胶的情形十分相似,降水变化的区域也和硫酸盐的保持一致。     

平流层和中层大气研究的进展

平流层和中层大气研究是20世纪70年代以来持续得到大气科学界和日地物理界共同关注的研究前沿.中国科学界在文化大革命结束后立即抓住这一前沿作为发展重点之一.20多年来,中国科学院大气物理研究所等单位较为系统地开展了这一方向的研究,并在一些方面进行了前沿性的工作.作者着重介绍以下几方面的进展:(1)平流层和中层大气探测设施与探测方法;(2)大气臭氧、平流层气溶胶的监测与分析;(3)行星波在中层大气环流与大气臭氧分布中的作用;(4)重力波在中层大气的传播特征与作用;(5)平流层-对流层交换的动力物理与化学问题.     

复合体系有机气体氧化生成二次有机气溶胶研究进展

生物源与人为源有机气体氧化形成的二次有机气溶胶(SOA)对气候变化和人类健康具有重要影响。SOA的产生与其前体物研究已取得了一些进展,但由于有机气体之间存在复合相互作用以及SOA形成机制复杂,目前对不同有机气体混合体系中SOA的形成认知还比较匮乏。因此,深入了解有机气体多源、复杂的相互作用,摸清有机气体的大气氧化机制、SOA的形成及影响等对深入理解真实大气有机气体化学演变具有指导意义。本文旨在了解复合体系有机气体氧化生成SOA的相关研究进展。一方面总结了复合体系有机气体产生SOA质量浓度、产率、成分、挥发性、光学性质等的变化,侧重于实验室复合体系有机气体氧化对SOA形成的多重影响以及SOA组成元素、分子构成的变化特征,并总结了目前实验室基于模型对复合体系SOA生成的模拟研究和拟合情况;另一方面探究了环境因素,如相对湿度(RH)、温度(T)以及无机气体,如氮氧化物(NO_x)、二氧化硫(SO₂)、氨气(NH₃)等对复合体系有机气体形成SOA的影响。     

2007-2017年中国沙尘气溶胶的三维分布特征及输送过程

利用最新发布的CALIPSO产品,构建了2007-2017年中国沙尘气溶胶的三维分布,并结合HYSPLIT-4模式和再分析数据,探讨了沙尘的三维输送过程。结果表明：中国的沙尘排放源区主要是塔克拉玛干沙漠和巴丹吉林沙漠,沙尘气溶胶出现频率分别为60%和35%。塔克拉玛干沙漠排放的沙尘主要（50%~70%）停留在源地0~6 000 m高度,少部分向东输送至甘肃和内蒙古;巴丹吉林沙漠排放的沙尘则主要向东输送。中国沙尘排放量在春季最大,向东输送最强;夏季,东亚夏季风限制了沙尘向东输送;秋季,沙尘排放减弱,输送强度和夏季相当;沙尘排放量在冬季最小,输送最弱。夏季,沙尘在输送过程中可被抬升至高度5 000 m以上,春季次之,秋、冬季的沙尘主要在低层大气输送。沙尘在向东输送的过程中被抬升并和当地人为污染物混合变为污染性沙尘,华北地区污染性沙尘出现频率高达30%;输送到海洋的沙尘也会与洋面上（0~3 000 m高度）的海盐气溶胶混合,出现频率约为10%。     

Preliminary comparison of trace metals in coastal aerosols between Qingdao and Liverpool

Aerosol samples were collected at two coastal suburban stations, Qingdao （China） in 1995-1996 and Liverpool （U.K.） in 1995, respectively. The samples were analyzed to determine the concentrations of trace metals （Cr, Zn, Cu, Co, Ni, Pb, V, and Cd） as well as A1, Fe and Mn. Data were examined to understand the difference of trace metals in aerosols between coastal zones downwind the developing area （near the Yellow Sea） and developed region （near the Irish Sea）. The results show that most elements at Qingdao have levels 4-5 times higher than those at Liverpool, particularly for the crust-dominated elements （e.g. Al, Fe and Mn）. Moreover, the aerosol composition at Qingdao is higher in spring than in summer, underlying the influence of westerlies and local emissions in combination, whereas seasonal change of aerosol composition is not significant at Liverpool. The enrichment factors for the crustal source elements （EFcrust） at Liverpool are much higher than those at Qingdao. The contributions from the pollutant source （Rp） for some trace metals like Cu, Pb, Zn and Cd are 〉90% at Qingdao and Liverpool, suggesting overwhelming anthropogenic contributions to these metals. The contributions from crustal source （Re） for trace metals tend to increase with higher aerosol levels and Al concentration at Qingdao, indicating a good correlation between the crust-dominated component and the air mass. At Liverpool, the Rc values for trace metals are positively correlated with Al concentrations instead of with aerosol mass, suggesting that Al in aerosols represents the crustal component even though the aerosols come from different sources.     

气溶胶气候效应的一维模式分析

本文首先采用一线辐射对流模式，分析了乡村型、城市型气溶胶和平流层气溶胶含量增加对全球地表气温的直接影响以及硫酸盐粒子含量增加对全球地表气温的间接影响。然后利用考虑了海洋热惯性作用的ＥＢＭ／ＢＤ模式，模拟了近百年来由于大气中硫酸盐粒子含量变化、火山爆发和大气温室气体浓度增加共同引起的全球地表平均气温变化。结果表明：气溶胶的气候效应在地气系统辐射收支和全球气温变化研究中起着非常重要的作用。