Spectroscopy Of PHOsgene for evaluating the injection of ChLorine into the Earth's Stratosphere (SOPHOCLES)

长寿命的人为含氯物种，如氯氟烃，是平流层氯的来源之一，并消耗臭氧层。《蒙特利尔议定书》减少了许多这类物种的浓度，臭氧层正在恢复。然而，寿命<6个月的极短寿命物质（VSLS），如二氯甲烷（DCM），是平流层最下层无机氯（Cly）的直接来源。DCM被广泛用作溶剂和生产泡沫剂。如果排放不受控制（DCM不受议定书控制），臭氧层的恢复将大大延迟。DCM目前占平流层Cl的约10%，随着这种增长和长寿命气体Cl的减少，其贡献预计将在未来几十年显著增加。VSLS平流层Cl输入分为两类：排放源气体（注源气体，SGI）和产物气体（注源气体，PGI）。在观测上，可以通过对流层上层的飞机仪器直接测量源气体，但是这些仪器不能提供监测所需的长期记录。卫星测量可以提供UTLS产品气体的全球覆盖和长期监测，但还不能提供任何Cl-VSLS源气体。大气化学实验-傅立叶变换光谱仪（ACE-FTS）测量了许多Cly物种，包括最重要的产物气体之一光气（COCl2）。光气是大气降解中最重要的Cl-VSLS: DCM和较少的CHCl3（氯仿）和C2Cl4（四氯乙烯）的常见中间体。Cl-VSLS的PGI估计可以从模型模拟中获得，然而，忠实地捕捉化学过程的复杂性和近似值使这些估算极具挑战性。特别是，关于对流层上层DCM氧化产生光气的文献资料有限。ace - fts得出的对流层上层光气丰度比模式计算的高约3倍。这些ACE-FTS对流层上层光气浓度的上升趋势为PGI与VSLS相关的增加提供了第一个直接观测证据。为了了解Cl-VSLS对臭氧消耗的日益增加的影响并做出未来的预测，验证和改进UTLS中源VSLS和产物气体的模型模拟非常重要。要做到这一点，我们需要调和模型和观测之间的不一致性。在这个项目中，我们的目标是通过新的实验室测量提供光气光谱的完整重新评估，从而更好地理解这些观测结果及其不确定性。精确的定量实验室光谱是从卫星仪器记录的大气光谱中提取微量气体丰度的基础。这项工作将为UTLS光气观测提供更可靠的卫星数据集，并为Cl-VSLS相关的光气PGI提供更好的约束。

Long-lived anthropogenic Cl-containing species such as chlorofluorocarbons are a source of stratospheric Cl and deplete the ozone layer. The Montreal Protocol has led to reductions in the concentrations of many such species, and the ozone layer is now recovering. However, very short-lived substances (VSLS) with lifetimes <6 months, e.g. dichloromethane (DCM), provide a direct source of inorganic chlorine (Cly) in the lowermost stratosphere. DCM is widely used as a solvent and in the production of foam agents. If emissions are left unchecked (DCM is not controlled by the Protocol), recovery of the ozone layer will be significantly delayed. DCM currently accounts for ~10% of stratospheric Cly, and its contribution is expected to increase significantly in coming decades along with this growth and as Cl from long-lived gases decreases.Stratospheric Cl input from VSLS is differentiated into two categories: emitted source gases (source gas injection, SGI) and product gases (product gas injection, PGI). Observationally, source gases can be measured directly by aircraft instruments in the upper troposphere, however these don't provide the long-term record needed for monitoring. Satellite measurements can provide global coverage and long-term monitoring of product gases in the UTLS, but not yet any Cl-VSLS source gases. The Atmospheric Chemistry Experiment - Fourier Transform Spectrometer (ACE-FTS) measures a number of Cly species, including one of the most important product gases, phosgene (COCl2).Phosgene is the common intermediate in the atmospheric degradation of the most important Cl-VSLS: DCM, and the less abundant CHCl3 (chloroform) and C2Cl4 (tetrachloroethene). Cl-VSLS PGI estimates are available from model simulations, however the complexity and approximations in faithfully capturing the chemical processes make these extremely challenging. In particular, there is limited information in the literature regarding the yield of phosgene from DCM oxidation in the upper troposphere. ACE-FTS-derived abundances of phosgene in the upper troposphere are higher than calculated by models by a factor of ~3. The positive trend in these ACE-FTS upper tropospheric phosgene concentrations provided the first direct observational evidence of the increase in PGI associated with VSLS.In order to understand the increasing impact of Cl-VSLS on ozone depletion and to make future predictions, it is important to validate and improve model simulations of source VSLS and product gases in the UTLS. To achieve this, we need to reconcile inconsistencies between model and observations. In this project, we aim to obtain a better understanding of these observations and their uncertainties by providing a complete re-evaluation of phosgene spectroscopy through new laboratory measurements. Accurate quantitative laboratory spectroscopy is fundamental for retrieving abundances of trace gas species from atmospheric spectra recorded by satellite instruments. This work will lead to more robust satellite datasets of phosgene observations in the UTLS, and provide a better constraint on the phosgene PGI associated with Cl-VSLS.