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Abstract
Abstract. To examine the effects of changes in climate, land cover and land use (LCLU), and anthropogenic emissions on fine particulate matter (PM2.5) between the 5-year periods 1981–1985 and 2007–2011 in East Asia, we perform a series of simulations using a global chemical transport model (GEOS-Chem) driven by assimilated meteorological data and a suite of land cover and land use data. Our results indicate that climate change alone could lead to a decrease in wintertime PM2.5 concentration by 4.0–12.0 µg m−3 in northern China, but to an increase in summertime PM2.5 by 6.0–8.0 µg m−3 in those regions. These changes are attributable to the changing chemistry and transport of all PM2.5 components driven by long-term trends in temperature, wind speed and mixing depth. The concentration of secondary organic aerosol (SOA) is simulated to increase by 0.2–0.8 µg m−3 in both summer and winter in most regions of East Asia due to climate change alone, mostly reflecting higher biogenic volatile organic compound (VOC) emissions under warming. The impacts of LCLU change alone on PM2.5 (−2.1 to +1.3 µg m−3) are smaller than that of climate change, but among the various components the sensitivity of SOA and thus organic carbon to LCLU change (−0.4 to +1.2 µg m−3) is quite significant especially in summer, which is driven mostly by changes in biogenic VOC emissions following cropland expansion and changing vegetation density. The combined impacts show that while the effect of climate change on PM2.5 air quality is more pronounced, LCLU change could offset part of the climate effect in some regions but exacerbate it in others. As a result of both climate and LCLU changes combined, PM2.5 levels are estimated to change by −12.0 to +12.0 µg m−3 across East Asia between the two periods. Changes in anthropogenic emissions remain the largest contributor to deteriorating PM2.5 air quality in East Asia during the study period, but climate and LCLU changes could lead to a substantial modification of PM2.5 levels.
Highlights
Over the recent decades atmospheric particulate matter (PM, or aerosols) has received considerable attention in East Asian countries due to its impacts on regional air quality, human health and climate change
With anthropogenic emissions fixed at present-day levels, the changes in wintertime PM2.5 resulting from both climate and land cover and land use (LCLU) changes combined between 1980 and 2010 are in the range of −12.0 to +6.0 μg m−3 in East Asia, with the maximum decrease found in the North China Plain (Fig. 9a)
We simulate the effects of changes in climate, land cover and land use (LCLU), and anthropogenic emissions between the two 5-year periods 1981–1985 and 2007–2011 on the surface concentrations of total PM2.5 and its components including sulfate, nitrate, ammonium, organic carbon (OC), and black carbon (BC) in East Asia using the GEOS-Chem chemical transport model driven by assimilated meteorological data and a suite of satellite- and survey-derived LCLU data
Summary
Over the recent decades atmospheric particulate matter (PM, or aerosols) has received considerable attention in East Asian countries due to its impacts on regional air quality, human health and climate change. We use a chemical transport model driven by past meteorological and land surface data to evaluate the individual and combined effects of climate and land cover changes in East Asia over 1980–2010, and compare these effects with that of increasing anthropogenic emissions. Wu et al (2012) predicted that changes in natural vegetation and anthropogenic land use over 2000–2050 would lead to higher summertime SOA over East Asia Most of these studies, except Jeong and Park (2013), are concerned with the effects of future climate change and/or land cover change on aerosols. The findings would shed light on the possible climate and land use “penalties” or benefits that might have exacerbated or offset the effect of anthropogenic emissions in the past, and provide a constraint for future air quality projections, which currently have large uncertainties for East Asia
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