Investigating Planetary Boundary Layer and Land Surface Model Schemes in the WRF Model for the Sierra Nevada Region

Abstract:

The Lake Tahoe Basin is located on the border of California and Nevada northeast of the Central Valley in the Sierra Nevada Mountains. Despite its pristine beauty and water clarity, the Lake Tahoe Basin is facing problems related to air pollution including ambient ozone levels. The meteorology in this region is unusually complex due to mountainous terrain and other topographical features. Thermally driven wind systems are a common phenomenon found in mountainous regions throughout the world. These wind systems, along with the structure of the atmospheric boundary layer are important for understanding the distribution and transport of atmospheric pollutants in complex terrain. Therefore, it is essential in air pollution modeling to correctly represent the planetary boundary layer (PBL) physics that governs the vertical mixing of pollutants and PBL height, where both impact the surface pollutant concentrations. Multiple PBL and Land Surface Model (LSM) parameterization schemes are available in the Weather Research and Forecast (WRF) model and have different assumptions determining the transport of mass, moisture and energy. During the period of July 21 -26, 2012, a field study was conducted in the Basin designed to characterize the precursors and pathways of secondary pollutant formation, including ozone and secondary organic aerosol (SOA). Using the observations obtained from the field study, this analysis looks at various WRF PBL schemes used in the Community Multiscale Air Quality (CMAQ) model and evaluates their performance for this area as well as investigates thermally forced small-scale processes within the Lake Tahoe Basin. The goal of this work is to understand the impact of PBL/LSM schemes on the micrometeorology in complex terrain in order to investigate the impact of transport phenomena on rural ozone concentrations in the Lake Tahoe Basin.