ABSTRACT

Modulation ...................................................... 48 2.4. Atmospheric Filamentation Experiments................... 49 2.5. Lidar Remote Sensing of Atmospheric Traces............ 51

2.6. Aerosols ........................................................................ 54 2.7. Conclusion.................................................................... 58 Acknowledgments.................................................................. 59 References.............................................................................. 59

2.1. INTRODUCTION

While light detection and ranging (lidar) allows the determination of three-dimensional distributions of atmospheric trace gases as well as information about the abundance, size, and phase of the aerosol, however, it is generally restricted to the detection of only one gaseous substance at a time, and does not allow the remote determination of aerosol chemical composition, as would, for example, be required to identify bioagents. On the contrary, long-path optical absorption methods like Fourier-transform infrared spectroscopy (FTIR) or differential optical absorption spectroscopy (DOAS) simultaneously yield precise concentration data of a large group of atmospheric constituents from the absorption of light from a broadband source, either natural (usually the Sun or the Moon) or artificial (lamp), along its path across the atmosphere. But they do not give access to the three-dimensional mappings allowed by lidar.