Evolution of Ozone and Particulate Matter during Pollution Events Using Raman Lidar
Document ID: 103
Master's Thesis
The Pennsylvania State University
The Graduate School
Department of Electrical Engineering
Abstract
An investigation of air pollution episodes using remote sensing provided a means of describing the impact of local meteorology on the development and dissipation of air pollution events. Lidar was used to measure atmospheric constituents and provided a continuous monitor of the lower atmosphere’s vertical structure during the NARSTO-NE-OPS (North American Research Strategy for Tropospheric Ozone - North East - Oxidant and Particle Study). The NE-OPS study was conducted in the Philadelphia urban environment where a combination of pollution sources exists. The PSU Lidar Atmospheric Profile Sensor (LAPS) instrument measured ozone, water vapor, temperature, optical backscatter, and extinction, and the Science and Engineering Services, Inc. Micro Pulse Lidar (MPL) measured backscatter. LAPS transmits a laser beam and measures the scattered radiation at several wavelengths of Raman scattered signals using multi-channel photon counting detection, and provides vertical profiles of atmospheric properties. The MPL provides vertical profiles of backscatter signal. Analysis of an interesting pollution episode that occurred on 21 August 1998 was performed, which exhibited the dramatic effects associated with pollutant precursor material transportation and temperature dependence. Time sequences of water vapor depict an aloft plume mixing downward into the rising convective boundary layer, which resulted in simultaneous increases of backscatter, extinction, and ozone at the surface. Surface ozone concentrations reached approximately 120 ppb in a short period of three hours, and particle scattering extinction values at 284 nm reached 3 km-1. A possible transport reservoir of the ozone precursors responsible for these increases is thought to be peroxyacetyl nitrate (PAN), which has a thermal dissociation rate that increases exponentially. Results from this episode demonstrate the importance of vertical mixing, horizontal transport, and storage of precursor and pollutant matter.
| Citation: | K. R. Mulik, "Evolution of Ozone and Particulate Matter during Pollution Events Using Raman Lidar", The Pennsylvania State University, Master's Thesis, May 2000, 68 pages |