Painting a More Colorful Picture of the Atmosphere: Hyperspectral Lidar for Characterization of Atmospheric Constituents

Sammanfattning

Atmospheric particles play a significant role in radiative forcing through light scattering and new methods are called for to better characterize their impact. Typical Lidar systems emit single wavelength light, not utilizing full spectral information from scattering measurements. This thesis aims to use a hyperspectral lidar system to measure the spectral dependence of scattering and absorption of different atmospheric constituents. This was done by emitting broad band short-wave infrared light and collecting the backscattered light on a 2D InGaAs detector, mapping wavelength on one axis and range on the other. The system was tested along a horizontal path over a range of 700 meters, where ambient measurements were made under different atmospheric conditions as well as controlled releases of aerosol plumes. The system successfully retrieved hyperspectral signals from multiple atmospheric constituents which revealed spectral features in absorption and scattering. From these measurements, wavelength dependent backscatter and attenuation coefficients could be calculated. The study demonstrates the capability of the hyperspectral lidar to characterize particulate matter for a broadband spectrum, which can provide information on microphysical properties. The broad applicability of the method showcased the possibility to measure simultaneous backscatter and absorption for different spectral bands, supporting future applications in atmospheric monitoring studies.