The processes that create ozone pollution in the summer can also trigger the formation of wintertime air pollution, according to a new study from researchers at the University of Colorado Boulder and NOAA, in partnership with the University of Utah. The team’s unexpected finding, published in the journal Geophysical Research Letters , suggests that in the US West and elsewhere, certain efforts to reduce harmful wintertime air pollution could backfire. In the US, Europe and Asia, PM is severe in urban areas in the winter when ammonium nitrate, NH 4 NO 3 , comprises an appreciable fraction of the total PM mass. A key control strategy is to reduce emissions of the limiting reagent. Using measurements from a recent field campaign in the Salt Lake Valley, Utah, which experiences high PM levels in winter, we demonstrate that emission control strategies can be evaluated using the same framework commonly used […]