On the Nexus of Climate, Energy and Air Quality in Coastal-Urban Environments

This presentation focuses on coastal cities – a nexus of climate, energy, and air quality.   The Urban Heat Island (UHI) effect is the result of surface energy balance changes and anthropogenic heat emissions which forms a two-way feedback.  In warm seasons, excess heat from the UHI is a major driver of tropospheric ozone production once combined with nitrogen emissions and with volatile organic compounds (VOCs). Building exhalations are also a major source of environmental emissions, via their ventilation systems. These systems emit VOCs and Volatile Compound products, which are suspected to be major contributors for ozone production. As such, there is direct positive feedback in warm seasons between extreme heat, energy demands, and sources for ozone production. In cold seasons, this nexus also prevails; cold climates motivate energy demands, which leads to pollutants from the gas or coal driven-building heating systems, enhancing the UHI which results in negative feedbacks.  We present a unified observation and modeling approach to investigate this nexus in the two end-use costal-cities cases of New York City and Houston.  Observations and modeling from two major summer field campaigns are used to explore ozone episode cases driven by heat waves. The modeling used an urbanized weather model, which incorporates a building energy model, and is coupled to a chemical physical model.  The modeling framework was validated against the wide range of field observations demonstrating that incorporating urban effects is indeed necessary for accurate prediction. Observations showed a complex spatial and temporal interaction between the surface meteorology, UHI, sea-breeze front, and the ozone peak ridge. Maximum ozone production takes place in the cities which is advected to the urban outskirts, where the sea-breeze collapses leading to ozone peaks.  Building energy use was found to be a key contributor to both UHI intensification and maximum ozone.