Lake Breeze Effects on Urban Climate and Air Quality in Chicago Using Microsoft Eclipse Network

Xiaoyu Chen, Jhao-Hong Chen, Peiyuan Li, Scott Collis, Rao Kotamarthi, Paytsar Muradyan, Ashish Sharma, Lu Xu, JIAN WANG, Washington University in St. Louis

     Abstract Number: 526
     Working Group: Urban Aerosols

Abstract
Over 100 low-cost air quality sensors were deployed across Chicago from July 2021 to March 2023 and provided high temporal and spatial resolution measurements of Particulate Matter (PM2.5), Ozone (O3), Nitrogen Dioxide (NO2), Carbon Monoxide (CO), relative humidity, and temperature. In this study, we utilize this dataset to investigate the effects of lake breezes on spatiotemporal variations of temperature and air quality in Chicago, which are poorly understood. Machine learning models were employed to calibrate the sensor network data based on reference measurements from EPA or MesoWest stations. Based on meteorological data, we identified 42 lake breezes events in 2022, with 79% occurring in spring and summer. These events typically last between 3 to 8 hours, with the majority of them (61%) starting between 11am and 1pm.We found strong temperature decreases along the lakeshore extending inland, with a maximum reduction of ~3.5℃ during lake breezes events, effectively mitigating heat stress in Chicago during summer. Following lake breeze arrival, ozone mixing ratio declines, potentially due to lower temperatures slowing down photochemical reactions and relatively lower precursor concentrations in the lake breezes. PM2.5 during lake breeze events exhibits varied trends depending on wind speed. High wind speed disperses pollutants and promotes ventilation over the city, resulting in decrease of PM2.5. Conversely, low wind speed leads to the stagnation of pollutants mainly from south of Chicago, increasing PM2.5 levels. The hygroscopic growth of aerosols under higher RH and a shallower boundary layer height during the lake breeze events may also contribute to the increase of PM2.5 concentrations. The lake breeze effects on urban climate and air quality in Chicago are compared to those in other coastal areas. Moreover, initial data and insights from Community Research on Climate and Urban Science (CROCUS) air quality and trace gas measurements are presented.