CLEARFOGG - Checking Layers of the Earths AtmospheRe For halogenated Ozone-depleting and Greenhouse Gases

据目前所知，大气中含有一些浓度低于十亿分之一的痕量气体。与其低浓度相反，这些气体可具有大的环境影响。众所周知，卤化碳在全球变暖中非常有效。例如，在2005年，仅两种卤烃CFC-11和CFC-12就造成了约14%的二氧化碳人为温室效应，而二氧化碳的丰度约为500，000倍（气专委，2007年）。尽管由于《蒙特利尔议定书》的规定，大部分氟氯化碳在大气中的含量正在减少，但其氟化替代品也具有很高的全球变暖潜力，而且正在迅速增加。此外，卤烃可加剧平流层臭氧的破坏。如果氯或溴从这些分子中释放出来，就会发生这种情况。特别是溴是一种非常有效的臭氧“杀手”，也是一个正在进行的科学辩论的对象。已知的有机溴化合物不能提供足够的溴来解释平流层中观察到的无机溴。全世界只有有限数量的已知卤化碳得到持续监测，有时还会发现新的卤化碳。有明显迹象表明，对流层和平流层中还存在其他氟化、氯化和溴化物质。该项目的目的是对地球大气层的各个“层”（边界层、自由对流层、热带对流层顶层和平流层）进行系统筛查，以发现未知的卤化碳。在建立了一个有能力的分析系统之后，对物质的搜寻将从地球仪周围的清洁空气地面站的样本开始，然后在对流层上部/平流层下部进行飞机观测，最后从平流层气球样本开始。对于检测到的新物质，将估计辐射强迫和大气寿命，以计算其全球变暖潜能值。如有必要，将为此目的进行新的红外截面测量，并进行辐射传递建模。来自偏远观测站的存档空气样本和来自极地深雪的积雪空气样本可以追溯到大约50年前，这些样本将提供长期趋势。此外，还将确定新的卤化碳对平流层臭氧消耗的影响。不仅将对以前未知的气体进行这种研究，而且重要的是，还将对那些具有辐射或平流层重要性的气体的全球分布进行广泛的测量，而目前对这些气体的测量很少;例如，具有平流层重要性的短寿命溴化、氯化和碘化有机气体。该项目将在东安格利亚大学进行，该大学在这一领域拥有丰富的经验和专业知识。

To current knowledge the atmosphere contains a number of trace gases with concentrations below one part per billion. In contrast to their low concentrations these gases can have large environmental effects. Notably halocarbons are known to be very effective in global warming. For instance, in 2005 the two halocarbons CFC-11 and CFC-12 alone contributed about 14% of the effect of CO2 to the anthropogenic greenhouse effect, while CO2 is about 500,000 times more abundant (IPCC, 2007). Although most of the CFCs are decreasing in the atmosphere due to regulation by the Montreal Protocol their fluorinated substitutes also have high global warming potentials and are increasing quickly. In addition, halocarbons can enhance the destruction of ozone in the stratosphere. This occurs if chlorine or bromine is released from these molecules. In particular bromine is a very effective ozone 'killer' and the object of an ongoing scientific debate. The known organic bromine compounds do not provide enough bromine to account for the observed inorganic bromine in the stratosphere. Only a limited number of known halocarbons are continuously monitored worldwide and at times new ones are identified. There are strong indications for other fluorinated, chlorinated and brominated substances to be present in the troposphere and stratosphere. The aim of the project is to perform a systematic screening of various 'layers' in the Earth's atmosphere (boundary layer, free troposphere, tropical tropopause layer and stratosphere) for unknown halocarbons. After establishing a capable analytical system, the search for substances will start with samples from clean-air ground-based stations around the globe, then proceeding with aircraft observations in the upper troposphere/lower stratosphere and finally with balloon samples from the stratosphere. For the detected novel substances the radiative forcing and atmospheric lifetimes will be estimated in order to calculate their global warming potentials. If necessary for this purpose new infrared cross section measurements will be conducted, and radiative transfer modelling carried out. Archived air samples from remote observatories and firn air samples from deep polar snow dating back about 50 years will provide access to long term time trends. Also the influence of the new halocarbons on stratospheric ozone depletion will be determined. Not only will this search for previously unknown gases be undertaken, but also, importantly, extensive measurements will be made of the global distribution of those gases of radiative or stratospheric importance for which very few measurements presently exist; for example short-lived brominated, chlorinated and iodinated organic gases of stratospheric significance. The project will be carried at the University of East Anglia which has has extensive experience and expertise in this area.