Gaoxuan Wang
PhD in Physics
thesis defended on
29th January 2018

Laboratoire de Physico-Chimie de l'Atmosphère - LPCA

Title and thesis summary
Oral & posters presentation


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Title and thesis summary

Development of photonic instruments for measurement of aerosols optical properties

Aerosols, emitted by anthropogenic and natural sources, strongly affect the radiative budget of the Earth by scattering or absorbing the solar radiation to provide a negative (cooling) or positive (warming) radiative forcing (RF) effect. This RF capacity is characterized by the aerosol single scattering albedo (SSA) and its complex refractive index (RI), determined by the aerosol optical properties (scattering, absorption and extinction). Despite several decades of research, the aerosol RF effects on Earth's climate are still known with large uncertainties (almost equal to the magnitude of the aerosol forcing). The in-situ accurate measurement of these parameters is a key challenge in atmospheric science and climate change research, which needs an significant improvement in the measurement precision of aerosol optical property in order to reduce the uncertainty in aerosol radiative forcing by at least 3-fold for well supporting regulatory decisions related to global climate change.

In this PhD research project, we propose to develop a "photonic albedometer" for simultaneous high precision measurements of wavelength-resolved aerosol optical properties in three major regions of the solar radiation spectrum between 300-1500 nm. The innovative photonic albedometer incorporates modern cavity enhanced absorption spectroscopy technique in conjunction with photoacoustic spectroscopy and integrating sphere approaches for direct and simultaneous measurements of aerosol extinction, absorption and scattering coefficients. The aerosol SSA and the complex RI will be then retrieved as a function of wavelength from these measured aerosol optical coefficients.

This work will be performed in the framework of the Labex project CaPPA for laboratory investigation (WP2) as well as for field in situ observation (WP3). In collaboration with the laboratoire d’Optique Atmosphérique (P. Goloub), the developed photonic albedometer operating at ground level will be used in synergy with other field-established instruments (such as particle soot absorption photometer, nephelometer etc.) to evaluate and combine various information sources in order to improve the number and the accuracy of the retrieved parameters. This will contribute to both National ORAURE (Observations en Réseaux des Aérosols à Usage de Recherches Environnementales) and European ACTRIS (Aerosol, Cloud and Trace gases Research InfrastuctureS) observing systems.

The proposed instrument is not limited to aerosol monitoring. Its ability of simultaneously measuring concentration of multiple trace gases (such as : NO2, CHOCHO, H2CO, NO3, HONO, SO2, etc.) makes this kind of photonic instrument a very promising analytical tool for applications in various fields: atmospheric chemistry, agriculture, environmental research along with air quality monitoring with high potential of technology transfer and commercialization.

Key words
Photonic instrumentation; Cavity enhanced absorption spectroscopy; Photoacoustic spectroscopy; Aerosol optical properties; in situ observation.

Supervisor: Weidong Chen (LPCA)
Co-supervisor: Eric Fertein (LPCA)

Financing: Région Nord-Pas-de-Calais / ULCO





Oral and posters presentation