Is global ozone recovering?

Thanks to the Montreal Protocol, the stratospheric concentrations of ozone-depleting chlorine and bromine have been declining since their peak in the late 1990s. Global ozone has responded: The substantial ozone decline observed since the 1960s ended in the late 1990s. Since then, ozone levels have remained low, but have not declined further. Now general ozone increases and a slow recovery of the ozone layer is expected. The clearest signs of increasing ozone, so far, are seen in the upper stratosphere and for total ozone columns above Antarctica in spring. These two regions had also seen the largest ozone depletions in the past. Total column ozone at most latitudes, however, does not show clear increases yet. This is not unexpected, because the removal of chlorine and bromine from the stratosphere is three to four times slower than their previous increase. Detecting significant increases in total column ozone, therefore, will require much more time than the detection of its previous decline. The search is complicated by variations in ozone that are not caused by declining chlorine or bromine, but are due, e.g., to transport changes in the global Brewer–Dobson circulation. Also, very accurate observations are necessary to detect the expected small increases. Nevertheless, observations and model simulations indicate that the stratosphere is on the path to ozone recovery. This recovery process will take many decades. As chlorine and bromine decline, other factors will become more important. These include climate change and its effects on stratospheric temperatures, changes in the Brewer–Dobson circulation (both due to increasing CO₂), increasing emissions of trace gases like N₂O, CH₄, possibly large future increases of short-lived substances (like CCl₂H₂) from both natural and anthropogenic sources, and changes in tropospheric ozone.     

平流层大气过程研究的前沿与重要性

当前全球气候变化,重大灾害性天气气候事件的预警预测,以臭氧洞出现和臭氧层变化引起的全球环境变化监测预测,以及对临近空间的开发利用已经引起大气科学界对处于对流层大气以上的平流层大气过程的重要关注。扼要介绍了当前这方面的研究前沿和重要应用领域,最后提出我国加强平流层大气过程研究的建议。     

全球变化条件下的平流层大气长期变化趋势

两个因素将对21世纪平流层气候变化产生重要作用。一个是温室气体增加,另一个是平流层臭氧的可能恢复。温室气体增加的辐射效应一方面造成地面和对流层变暖,另一方面却导致平流层变冷,而臭氧层恢复的辐射效应则导致平流层变暖。在温室气体增加和臭氧恢复这两种相反因素作用下的平流层温度如何变化是所关心的主要问题。为了预估平流层温度在21世纪的变化,使用了辐射—对流模式进行了敏感性实验,另外,也对他人进行的化学—气候耦合模式（CCM）模拟结果进行了分析。这些模拟结果表明,在21世纪平流层中上层（60～1 hPa）将变冷,而下层（150～60 hPa）变暖。这说明在平流层中上层温室气体的冷却效应将起主导作用,而臭氧恢复的加热效应在平流层下层相对更为重要。CCM的模拟结果表明,臭氧恢复最显著的区域在平流层上层（3 hPa附近）,与最大降温区一致,说明温室气体增加将有利于平流层上层臭氧恢复。CCM的模拟结果还表明,平流层两极地区在冬半年存在变暖的现象。根据已有的研究结果,极区变暖与平流层行星波活动增强有关,动力、热力和化学之间的正反馈作用也有可能对极区变暖有重要的贡献。     

臭氧变化及其气候效应的研究进展

综述了近２０年来臭氧变化的规律和机制及其气候效应等领域的研究进展,指出对流层臭氧（主要在北半球）增加、平流层臭氧减少和臭氧总量减少是全球臭氧的变化趋势,原因主要是人类活动导致的ＮＯｘ、ＮＭＨＣ、ＣＯ、ＣＨ４等对流层臭氧前体物的增加和ＮＯｘ、Ｈ２Ｏ、Ｎ２Ｏ、ＣＦＣｓ等平流层臭氧损耗物质的增加。臭氧变化引起的气候效应表现在对流层臭氧的增加将带来地表和低层大气的升温,平流层臭氧的减少则可能导致地表和低层大气的升温或降温。将全球或区域气候模式和大气化学模式进行完全耦合来研究臭氧变化的气候效应是一种十分有效的手段,具有广阔的应用前景。     

全球大气臭氧层的主要特征和变化趋势

根据全球臭氧地面站（Ｄｏｂｓｏｎ站、Ｂｒｅｗｅｒ站、Ｍ８３和Ｍ１２４ａｌ）总量资料、臭氧探空廓线资料和雨云卫星（ＴＯＭＳ、ＳＡＧＥⅠｆｏＳＡＧＥⅡ）臭氧总量和廓线资料，给出南、北半球特别是南极地区平流层臭氧主要特征和变化趋势。结果表明，无论是中、低纬地区还是高纬地区（特别是南极地区的“臭氧洞”）臭氧总工从７０年代开始呈下降趋势，特别是近十几年来有加剧下降之势，这是各国政府和科学家极为关注的环境和气候问题。此外，还对臭氧总量变化趋势的各种解释作了综述。     

Chlorine in the stratosphere

This paper reviews the various aspects of chlorine compounds in the stratosphere, both their roles as reactants and as tracers of dynamical processes. In the stratosphere, reactive chlorine is released from chlorofluorocarbons and other chlorine-containing organic source gases. To a large extent reactive chlorine is then sequestered in reservoir species ClONO₂ and HCl. Re-activation of chlorine happens predominantly in polar winter vortices by heterogeneous reaction in combination with sunlight. Catalytic cycles involving Cl, ClO, BrO, Cl₂O₂, ClO₂, and others like NO, NO₂, OH, and HO₂ remove odd oxygen (ozone and atomic oxygen) from the atmosphere. Under an ozone hole condition, the ClO dimer cycle is particularly important, while in mid-latitudes the short-lived reservoir HOC1 has some importance. Solar proton events can also affect stratospheric chlorine chemistry, but whether solar protons effectively activate or deactivate chlorine was shown to depend on illumination conditions. The lifetime of chlorofluorocarbons has an impact on the availability of ozone destructing substances in the stratosphere and depends on the Brewer-Dobson circulation which controls at which altitudes and how long an air parcel is exposed to photochemistry. In turn, the chlorine-containing source gases can be used as tracers to constrain the age of stratospheric air and thus to diagnose the Brewer-Dobson circulation. The use of complementary measurement systems was essential to extend our knowledge on chlorine-containing compounds in the stratosphere. ClO is best measured by remote sensing in its rotational bands in the far infrared and microwave region. For HOC1 the far infrared bands are ideal, but some substantial information was also gained with microwave and mid-infrared measurements. ClONO₂ is only measured in the thermal infrared, while HCl has a measurable signal in the microwave, far infrared and mid-infrared regions. The mid-infrared HCl lines, however, are situated at wavelengths where blackbody emission at terrestrial temperatures is so low that infrared measurements of HCl are possible only in solar absorption geometry, but not in thermal emission. Chlorine source gases are most accurately measured by air sampling techniques, while global coverage can only be achieved by satellite-borne thermal infrared measurements. In epistemological terms, research on stratospheric chemistry and particularly the role of chlorine compounds used various scientific concepts from deductive reasoning, falsificationism, abductive reasoning and so-called “puzzle-solving within normal science”. The structuralist theory of science with the concept of non-statement view of theories, however, seems to be best applicable to stratospheric chlorine research of the recent decades.     

平流层-对流层交换研究进展

平流层与对流层之间的物质输送和混合（STE）是控制自然和人为排放的化学痕量物质对大气成分影响的一个重要过程。STE可以影响温室气体在上对流层和下平流层中的垂直分布,进而影响气候。要预报全球气候变化就必须了解平流层与对流层之间动力、化学及辐射的耦合。从 STE研究的尺度问题,热带和中纬度地区STE研究以及我国STE研究现状进行了评述。STE具有多种尺度和形式,热带外平流层由波强迫驱动的全球尺度环流,可以诊断长时间尺度的STE,它不能充分描述短时间尺度过程。热带外低平流层环流不能简单地描述为纬向平均,要正确描述痕量气体的分布必须包含纬向非对称的天气尺度过程。热带地区的滴漏管理论提供了一个新的诊断 STE框架。目前对中纬度地区对流层顶折叠和切断低压的研究是比较充分的。     

火山活动与气候变化研究进展

综述了火山活动对气候影响的研究进展。不同岩浆成分及喷发类型的火山活动对气候的影响不同：中酸性普林尼（Pl inian）式火山喷发主要造成气候变冷和臭氧层破坏,它导致气候变化的时间较短,但空间范围较大;大火成岩省造成气候变化的时空范围及程度均较大,它能够导致地表温度、海平面大幅度变化,最终引起生物灭绝;中小规模玄武质裂隙式喷发主要造成火山盆地内气候较大幅度变化,但对气候影响的持续时间较短,主要气候效应是导致附近地区温度快速下降和形成酸雨。简要阐述了第四纪火山活动的特点。     

平流层微量气体变化趋势的研究

采用HALOE提供的1992—2005年的资料,分析了平流层几种微量气体（臭氧、HCl,HF,NO,NO2,水汽和甲烷）的混合比在不同高度、不同纬度带的变化趋势, 以期为研究平流层的辐射和化学过程提供一些有用的数据。结果表明,在不同纬度带这些微量气体的变化特征并不相同,在不同高度上他们的变化特征也不大一样。这14年臭氧的变化趋势与其他几种微量气体的变化趋势对比表明,在平流层上层,1990年代中期以后臭氧浓度的恢复比较明显,而且这14年臭氧的变化趋势与HCl、HF和水汽的变化趋势是相反的。在平流层中层臭氧的变化趋势复杂一些,除一些微量成分对它的破坏外,还受到其它因素的影响。但1997—2002年臭氧混合比增大,与HCl、NO,NO2和水汽混合比的减小趋势是相反的,这说明《蒙特利尔条约》及其它环保措施的实施对平流层中层臭氧浓度的恢复也已初见成效。     

中国大气臭氧探空仪的研制和应用

地球大气中的臭氧一直是全球气候和环境变化研究中的重要内容。大气臭氧探空系统是当前直接获得地球大气臭氧垂直结构资料的直接探测系统,同时也是为卫星臭氧探测和激光雷达臭氧探测等提供对比和定标的有力手段。中国大气臭氧探空仪的研制工作起步较晚且进展缓慢,这在一定程度上妨碍了中国大气臭氧高空探测业务化的进程。首次报道了中国大气臭氧高空探测业务化进展状况,重点报告中国自行研制的大气臭氧探空仪的结构和技术性能指标,讨论了中国大气臭氧探空仪主要技术性能指标与芬兰Vaisala臭氧探空仪的比对结果,并给出该系统在北京、南极等地区应用施放中所得到的部分探测结果。同时对中国大气臭氧高空探测业务化方面的近期任务提出了建议。     

拉萨上空大气臭氧垂直分布的高空气球探测

用臭氧探空仪于1998年8月和10月测量了在拉萨上空的臭氧垂直分布,并与河北香河的观测资料进行了对比。结果表明,拉萨上空对流层臭氧浓度较低,在25～26 km之间臭氧分压最大,在30～34 km之间混合比最大。从典型的臭氧垂直分布廓线推算出大气臭氧总含量为261.6DU。     

气候学研究进展

回顾了80年代到90年代中期，气候学研究在几个方面的重要进展。共分析了五个问题：①20世纪气候变率，重点讨论年代际变率及气候突变；②ENSO模拟与预测，总结比较了各种模式的模拟与预测结果，着重讨论了90年代前半期ENSO发展的特点；③ENSO与季风，指出亚洲夏季风在ENSO循环中的重要作用；④气候可预报性研究，总结了月、季预报试验，介绍了用观测下边界强迫AGCM的研究结果；⑤气候变化成因分析，着重说明温室效应研究的不确定性及自然因子如太阳活动、火山活动在气候变化中的作用。     

近四年来我国气候数值模拟与预报研究的进展

近年来，我国在气候问题中的数值模拟式研究方面有了相当大的发展。这主要表现在气候模式水平的迅速提高，以及利用气候模式进行了大量的气候数值模拟和预报试验研究工作。对我国１９９１￣１９９４年在这方面的主要研究进展进行了系统的总结。     

Ozone decline and its effect on night airglow intensity of Na 5893 Å at Dumdum (22.5°N, 88.5°E) and Halley Bay (76°S, 27°W)

The paper presents the effect of O₃ depletion on night airglow emission of Na 5893 Å line at Dumdum (22.5°N, 88.5°E), India and Halley Bay (76°S, 27°W), a British Antarctic service station. Calculations based on chemical kinetics show that the airglow intensity of Na 5893 Å line will also be affected due to the depletion of O₃ concentration. The nature of yearly variation and seasonal variation of the intensity of Na 5893 Å line for the above two stations are shown and compared. It is shown that the rate of decrease of intensity of Na 5893 Å line is comparatively more at Halley Bay due to the dramatic decrease of Antarctic O₃ concentration. A possible explanation for this dramatic decrease of Antarctic O₃ concentration is also mentioned.     

中高层大气瞬态发光事件（TLEs）及可能的影响

中高层大气瞬态发光事件（TLEs）是发生于活跃雷暴上空平流层和中间层的一类快速大气放电现象。根据光辐射的形态特征和发生位置的不同,可将已发现的TLEs归纳为4类：由电离层快速向下发展的Red Sprites(又称红色精灵,红闪);由雷暴云顶部向上发展的Blue Jets（又称蓝色喷流,蓝激流）;由闪电激发的低电离层区域的圆环状放电ELVEs(Emissions of Light and VLF perturbation due to EMP Sources,又称光辐射和EMP源引起的甚低频扰动) 和由云顶向电离层快速向上发展的Gigantic Jets(又称巨大喷流)。对已有的TLEs现象学和形态特征的观测事实以及物理机制和理论研究等进行了回顾,讨论了TLEs对平流层和中间层大气以及电离层的可能影响,并提出了目前在TLEs理论方面尚未解决的问题,指出了进一步观测和理论研究的必要性。