Also discussed here: Greater air stagnation could lead to more deaths(EnvironmentalResearchWeb, Jan. 25, 2013)
Today we look at an application global climate models to estimate what impact changes in the atmospheric circulation would have on stagnation and as consequence, air pollution, around the world. Stagnation of the air near the ground occurs when there is light wind, little rainfall and is often accompanied by a temperature inversion which traps local emissions and allows them to accumulate. Large cities, especially in North America (New York, Atlanta, Mexico City), Europe (Rome) and Asia(New Delhi, Shanghai and Beijing), are expected to have 25% more days of stagnate air by the end of the century. This, along with the increase in the number of hot spells which promotes smog formation, is likely to aggravate the impact of air pollution on health.
Key Quotes:
“Air stagnation is characterized by meteorological conditions that lack contaminant-scavenging capabilities and minimize the horizontal dispersion and vertical escape of pollutants..Stagnation tends to occur in areas where the temperature is fairly even, the atmosphere is stable and there is little rainfall…it allows ozone and particulate matter to accumulate near the Earth's surface.”
“Projected changes in late-21st century air stagnation are spatially heterogeneous, with increases of up to 12–25% relative to the late-20th century occurring over many of the world’s industrialized population centers, including those in the eastern United States, Mediterranean Europe, and eastern China”
“ Substantial increases (>9 days yr1) in stagnation occurrence are also projected for portions of Central America, northern South America, southern Africa, central Asia, the Persian Gulf region and northern India”
“the projected autumn and winter increases in stagnation days over eastern China and the eastern United States are largely caused by changes in the 500 mb wind field.. global warming will lead to a northward shift of the northern hemisphere polar jet stream and/or fewer southward excursions of the storm track due to a reduction in cyclogenesis”
“projected seasonal regional temperature increases have the potential to amplify pollutant concentrations due to increases in chemical reaction rates and/or make non-summer stagnation changes more relevant, should temperatures in non-summer seasons increase sufficiently to exceed critical chemical reaction thresholds”
“many industrial population centers, including Mexico City, Atlanta, New York City, Rome, New Delhi, Shanghai and Beijing, and the regions that surround them, could experience 12–25% relative increases (3–18C days yr1) in stagnant atmospheric conditions,”
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