报告题目：Photonics for Atmospheric Sensing : Challenges and Opportunities

报告人：Weidong CHEN

单位：Laboratoire de Physicochimie de l’Atmosphère, Université du Littoral C？te d’Opale

189A, Av. Maurice Schumann, 59140 Dunkerque, France

时间：9月7日（周三）上午10：00

地点：大气所40号楼-912会议室

Abstract

Ongoing changes in atmospheric composition due to both natural and anthropogenic influences affect not only climate and atmospheric processes but also have a negative impact on the air quality (hence human health), the hydrological cycle/ecosystems, and consequently on economic developments. Understanding and prediction of future changes in atmospheric composition requires reliable long-term estimates of sources and sinks appropriate to particular emission management scenarios with very high accuracy and precision observations of the abundance of key atmospheric species as well as their isotopes. A validation of numerical models requires a comprehensive comparison with multiple types of observations/measurements (from satellite-, aircraft-, balloon-platform, and ground-based observation network) with regional resolution and global coverage. This has been a key driving force for the development of new research infrastructures for sensitive, selective, accurate and precise monitoring trace concentration of atmospheric gases. Contrary to long-lived species such as greenhouse gases, accurate and precise direct concentration measurements of reactive short-lived species represent a real challenge because of their very short lifetime (1 to 100 s) and very low concentration in the atmosphere (down to 106 molecules/cm3, corresponding to 0.1 pptv atstandard temperature and pressure). This requires the use of advanced analytical technology capable of performing interference-free high sensitivityin situ and real time monitoring.

In recent years, significant breakthroughs in photonics and spectroscopic measurement techniques have been made. In this presentation, we report on our recent progress in instrumental development for monitoring of photochemically activespecies (OH, HONO, NO3, NO2) playing a critical role in atmospheric chemistry. Modern photonic sources (Quantum cascade laser,  distributed feedback diode laser, light emitting diode) were implemented in conjunction with high-sensitivity spectroscopic techniques such as Faraday rotation spectroscopy (FRS), cavity enhanced absorption spectroscopy  (including off-axis integrated cavity output spectroscopy, OA-ICOS and incoherent broadband cavity enhanced absorption spectroscopy, IBBCEAS), and multipass cell based direct absorption spectroscopy (DAS). Application to monitoring of NO3 radicals in a smog chamber will be presented.