Abstract
We examine the impact of future climate change on regional air pollution meteorology in the United States by conducting a transient climate change (1950–2052) simulation in a general circulation model (GCM) of the Goddard Institute of Space Studies (GISS). We include in the GCM two tracers of anthropogenic pollution, combustion carbon monoxide (COt) and black carbon (BCt). Sources of both tracers and the loss frequency of COt are held constant in time, while wet deposition of BCt responds to the changing climate. Results show that the severity and duration of summertime regional pollution episodes in the midwestern and northeastern United States increase significantly relative to present. Pollutant concentrations during these episodes increase by 5–10% and the mean episode duration increases from 2 to 3–4 days. These increases appear to be driven by a decline in the frequency of mid‐latitude cyclones tracking across southern Canada. The cold fronts associated with these cyclones are known to provide the main mechanism for ventilation of the midwestern and northeastern United States. Mid‐latitude cyclone frequency is expected to decrease in a warmer climate; such a decrease is already apparent in long‐term observations. Mixing depths over the midwest and northeast increase by 100–240 m in our future‐climate simulation, not enough to compensate for the increased stagnation resulting from reduced cyclone frequency.
Highlights
Introduction[2] Long-term projections for surface air quality in the United States must account for future changes in emissions and for changes in climate
[1] We examine the impact of future climate change on regional air pollution meteorology in the United States by conducting a transient climate change (1950 – 2052) simulation in a general circulation model (GCM) of the Goddard Institute of Space Studies (GISS)
[3] We focus on the eastern and midwestern United States where pollution episodes tend to extend over regional scales greater than 500,000 km2 [Logan, 1989; Eder et al, 1993], in contrast to the more mountainous west where they tend to be local and affected by topography [e.g., Pun and Seigneur, 1999; Winner and Cass, 1999]
Summary
[2] Long-term projections for surface air quality in the United States must account for future changes in emissions and for changes in climate. More important may be the sensitivity to changes in mixing depths, frequency of stagnation episodes, and synoptic-scale circulations [e.g., Logan, 1989; Vukovich and Sherwell, 2002] We explore these effects here with a general circulation model (GCM) transient simulation of 2000 – 2050 climate change. For this purpose, we use a GCM transient model simulation for 2000 – 2050 including two simple tracers of anthropogenic pollution, combustion carbon monoxide (CO) and black carbon aerosol (BC). Emissions for both tracers are held constant over the simulation, so that any trends in concentration are driven solely by climate change
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