Characterization of Low-Level Jets and their Influence on Air Pollution Using Raman Lidar and Wind Profiling Radar/RASS
Document ID: 13
Master's Thesis
The Pennsylvania State University
The Graduate School
Department of Electrical Engineering
Abstract
Raman lidar employed simultaneously with wind measurements of a radar/RASS (Radio Acoustic Sounding System) profiler are used to characterize features of nocturnal jets or Low-Level Jets (LLJ’s) and the effect they have on the local meteorology. While the radar/RASS measurements document the kinematic and thermodynamic structure by identifying the velocity and virtual temperature distributions, the PSU Lidar Atmospheric Profile Sensor (LAPS) observations provide high temporal and spatial resolution of the water vapor mixing ratio, temperature, ozone concentration, and optical extinction. Data was obtained from the two instruments during the NARSTO-NE-OPS (North American Research Strategy for Tropospheric Ozone – North East – Oxidant and Particle Study) case studies, which was conducted in the Philadelphia urban environment during the summers of 1999, 2001 and 2002. The PSU LAPS instrument uses Raman scattering techniques to provide vertical profiles of the atmospheric properties. The wind profiling radar is a pulsed Doppler radar and provides continuous profiles of the wind characteristics. The PSU Raman lidar and the radar/RASS profiler are used to delineate the physical characteristics of the LLJ, its development, evolution and the variations in observed parameters associated with the LLJ phenomena. LLJ’s have been associated with high ozone events since both LLJ’s and high ozone episodes occur under similar meteorological conditions. An important finding is the intrusion of drier air with ozone and precursor concentrations as the LLJ become a conveyor of air from the western boundary region during the early hours of the morning. This transport reservoir increases the concentrations of pollutants drastically when it is mixed down to the surface by convective heating and by bursting events. Analysis of the data revealed that low-level jets were present on 7 out of 8 nights prior to days when ozone concentrations exceeded 100 ppbv. The results obtained clearly indicate the low-level jet to be an important mechanism in the generation of pollution episodes due to its capability to transport pollutant and precursor materials over long distances during the night and produce high concentrations of pollutants the following day.
Keywords: low level jets, Wind Radar, Radio Acoustic Sounder System (RASS), air pollution
| Citation: | S. J. Verghese, "Characterization of Low-Level Jets and their Influence on Air Pollution Using Raman Lidar and Wind Profiling Radar/RASS", The Pennsylvania State University, Master's Thesis, August 2003, 85 pages |