The Characteristics of the Chicago Lake Breeze and Its Effects on Trace Particle Transport: Results from an Episodic Event Simulation

Abstract The lake-breeze circulation that forms over Lake Michigan during the summer influences the Chicago, Illinois, metropolitan area’s weather in several ways. Of particular significance is the circulation’s effect on the dispersion of pollutants such as ozone and aerosols produced in and around the city. To investigate these effects, the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) was used to perform numerical simulations for two lake-breeze events—one in July 1999 and another in July 2002. The model runs were verified with data from several locations around the Chicago area. The simulated breeze circulation decreased the rate of increase in air temperature while penetrating roughly 12 km inland and lasting about 8 h, in reasonable agreement with observations. Furthermore, the inland penetration distance was related to the strength of the maximum vertical velocity within the front. Calculations of trajectories and transport of particle...