The role of climate and emission changes in future air quality over southern Canada and northern Mexico

[摘要] Potential impacts of global climate and emissions changes on regional airquality over southern (western and eastern) Canada and northern Mexico areexamined by comparing future summers' (i.e., 2049–2051) average regionalO₃ and PM_2.5 concentrations with historic concentrations (i.e.,2000–2002 summers). Air quality modeling was conducted using CMAQ andmeteorology downscaled from the GISS-GCM using MM5. Emissions for NorthAmerica are found using US EPA, Mexican and Canadian inventories andprojected emissions following CAIR and IPCC A1B emissions scenario. Highertemperatures for all sub-regions and regional changes in mixing height,insolation and precipitation are forecast in the 2049-2051 period. Futureemissions are calculated to be lower over both Canadian sub-regions, buthigher over northern Mexico. Global climate change, alone, is predicted toaffect PM_2.5 concentrations more than O₃ for the projections usedin this study: average daily maximum eight (8) hour O₃ (M8hO₃)concentrations are estimated to be slightly different in all examinedsub-regions while average PM_2.5 concentrations are estimated to behigher over both Canadian sub-regions (8% over western and 3% overeastern) but 11% lower over northern Mexico. More days are forecast whereM8hO₃ concentrations are over 75 ppb in all examined sub-regions but thenumber of days where PM_2.5 concentration will be over 15 μg/m³ is projected higher only over western Canada. Climate changecombined with the projected emissions lead to greater change in pollutantconcentrations: average M8hO₃ concentrations are simulated to be 6%lower over western Canada and 8% lower over eastern Canada while averagePM_2.5 concentrations are simulated to be 5% lower over westernCanada and 11% lower over eastern Canada. Although future emissions overnorthern Mexico are projected higher, pollutant concentrations are simulatedto be lower due to US emissions reductions. Global climate change combinedwith the projected emissions will decrease average M8hO₃ 4% andPM_2.5 17% over northern Mexico. Significant reductions in the numberof days where M8hO₃ concentrations are over 75 ppb and PM_2.5 concentration over 15 μg/m³ are also projected with a significantreduction in peak values.

[学科分类] 大气科学