Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Diode-laser-based high spectral resolution LIDAR(Montana State University - Bozeman, College of Engineering, 2021) Colberg, Luke Stewart; Chairperson, Graduate Committee: Kevin S. RepaskyThis thesis describes the design, construction, and testing of a high spectral resolution lidar (HSRL) as a part of a combined HSRL and differential absorption lidar (DIAL) system. The combined HSRL and DIAL instrument is constructed using the MicroPulse DIAL (MPD) architecture and uses distributed Bragg reflector lasers. The MPD architecture is unique because it is eye-safe and cost-effective; therefore, it is ideal for creating a network of ground-based lidars. This instrument is designed for thermodynamic profiling of the lower troposphere. A network of these instruments would be helpful for wide-scale atmospheric monitoring for weather forecasting and climate science. The purpose of the HSRL is to retrieve the optical properties of aerosols in the lower troposphere. The HSRL uses the DIAL offline laser, which has a wavelength of 770.1085 nm, and a potassium vapor cell as the spectral filter. The data retrieved from the HSRL provides the aerosol backscatter coefficient and the backscatter ratio up to an altitude of 7 km during nighttime operation and 5 km during daytime operation. The time resolution for these measurements is 5 minutes, and the range resolution is 150 m. These aerosol optical properties are valuable for aerosol studies and climate modeling; aerosols introduce the most significant degree of uncertainty in modeling the heat flux of the atmosphere. Additionally, these aerosol optical properties can be used to find the planetary boundary layer height (PBLH). The planetary boundary layer controls the exchange of heat, water vapor, aerosols, and momentum between the surface and the atmosphere. It has been demonstrated that the PBLH strongly affects turbulent mixing, convective transport, and cloud entrainment, which makes the PBLH an important parameter for weather forecasting and climate modeling. Despite its significance in atmospheric science, there is no standard method for defining the PBLH. A retrieval method for finding the daytime PBLH using HSRL data is proposed, and data comparisons to radiosonde PBLH retrievals are provided. The algorithm shows a good agreement with the radiosonde retrievals for conditions with a well-behaved boundary layer.Item Two wavelength Lidar instrument for atmospheric aerosol study(Montana State University - Bozeman, College of Engineering, 2008) Hoffman, David Swick; Chairperson, Graduate Committee: Kevin S. RepaskyA two-color lidar instrument and inversion algorithms have been developed for the study of atmospheric aerosols. The two-color lidar laser transmitter is based on the collinear fundamental 1064 nm and second harmonic 532 nm output of a Nd:YAG laser. Scattered light is collected by the two-color lidar receiver using a Schmidt-Cassegrain telescope with the 532 nm channel monitored using a gated photomultiplier tube (PMT) and the 1064 nm channel monitored using an avalanche photodiode (APD). Data is collected from the PMT and APD using a 14 bit 200 MHz data acquisition card. The lidar inversion algorithm developed to analyze the data collected by the two-color lidar is based on a constant lidar ratio assumption at both the 1064 nm and 532 nm wavelengths with the constrained ratio aerosol model (CRAM) providing the initial lidar ratios at the two wavelengths to complete the lidar inversion. Data from the CALIOP lidar on board the CALIPSO satellite are presented to verify software algorithm performance. Data from the two-color lidar are then presented demonstrating the two-color lidar instrument's capabilities. The analysis of these data identifies smoke and industrial aerosols in the atmosphere above Bozeman. Finally an error analysis of the lidar instrument and accompanying analysis software is presented. The findings of this analysis are that error introduced by the APD and PMT is dominant; the error introduced by the optical detectors is much larger than the error from other sources examined such as quantization error, and the error associated the use of numerical integration in the data analysis algorithm.