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How urban areas can affect the interaction between biogenic carbons & anthropogenic pollutants

Speaker: Young-Hee Ryu, Postdoctoral Research Associate
Series: CEE Departmental Seminars
Location: Engineering Quad E225
Date/Time: Friday, November 8, 2013, 12:00 p.m. - 1:30 p.m.

Abstract:

Exact Title: How urban areas can affect the interaction between biogenic carbons and anthropogenic pollutants, and toward further understanding of urban land surfaceatmosphereinteraction

The land cover changes due to urbanization markedly alter the surface characteristics, surface energy balance, boundary layer, and local circulation, and hence the urbanmodified local meteorology correspondingly can affect urban air quality. In this study, the impacts of urban land-surface forcing on ozone air quality during a high ozone (O-3) episode in the Seoul metropolitan area, South Korea, are investigated using a highresolution chemical transport model (CMAQ). Under fair weather conditions, the temperature excess (urban heat island) significantly modifies boundary layer characteristics/structures and local circulatio s, which results in an increase in O3 levels in the urban area of 16 ppb in the nighttime and 13 ppb in the daytime. Enhanced turbulence in the deep urban boundary layer dilutes pollutants such as NOx, and this contributes to the elevated O3 levels through the reduced O3 destruction by NO in the NOx-rich environment. The advection of O3 precursors over the mountains near Seoul by the prevailing valley-breeze circulation in the mid- to late morning results in the build-up of O3 over the mountains in conjunction with biogenic volatile organic compound (BVOC) emissions there. As the prevailing local circulation in the afternoon changes to urbanbreeze circulation, the O3-rich air masses over the mountains are advected over the urban area. The urban-breeze circulation exerts significant influences on not only the advection of O3 but also the chemical production of O3 under the circumstances in which both anthropogenic and biogenic (natural) emissions play important roles in O3 formation. To better understand urban land surface–atmosphere interactions, a further development of an urban canopy model that contains more physical processes occurring in urban areas is required. The ongoing development of an urban canopy model and the ongoing research results will be briefly introduced.