China's international trade and air pollution in the United States
Lin J.-T. *, Pan, D. (undergraduate), et al.
Proceedings of the National Academy of Sciences, 111(5): 1736-1741, 2014
China is the world’s largest emitter of anthropogenic air pollutants, and measurable amounts of Chinese pollution are transported via the atmosphere to other countries, including the United States. However, a large fraction of Chinese emissions is due to manufacture of goods for foreign consumption. Here, we analyze the impacts of trade-related Chinese air pollutant emissions on the global atmospheric environment, linking an economic-emission analysis and atmospheric chemical transport modeling. We find that in 2006, 36% of anthropogenic sulfur dioxide, 27% of nitrogen oxides, 22% of carbon monoxide, and 17% of black carbon emitted in China were associated with production of goods for export. For each of these pollutants, about 21% of export-related Chinese emissions were attributed to China-to-US export. Atmospheric modeling shows that transport of the export-related Chinese pollution contributed 3–10% of annual mean surface sulfate concentrations and 0.5–1.5% of ozone over the western United States in 2006. This Chinese pollution also resulted in one extra day or more of noncompliance with the US ozone standard in 2006 over the Los Angeles area and many regions in the eastern United States. On a daily basis, the export-related Chinese pollution contributed, at a maximum, 12–24% of sulfate concentrations over the western United States. As the United States outsourced manufacturing to China, sulfate pollution in 2006 increased in the western United States but decreased in the eastern United States, reflecting the competing effect between enhanced transport of Chinese pollution and reduced US emissions. Our findings are relevant to international efforts to reduce transboundary air pollution.
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Tropospheric carbon monoxide over the Pacific during HIPPO: Two-way coupled simulation of GEOS-Chem and its multiple nested models
Yan, Y.-Y., Lin, J.-T. *, et al.
Atmos. Chem. Phys., 14, 12649-12663, doi:10.5194/acp-14-12649-2014, 2014
Global chemical transport models (CTMs) are used extensively to study air pollution and transport at a global scale. These models are limited by coarse horizontal resolutions that do not allow for a detailed representation of small-scale nonlinear processes over the pollutant source regions. Here we couple the global GEOS-Chem CTM and its three high-resolution nested models to simulate the tropospheric carbon monoxide (CO) over the Pacific Ocean during five High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) campaigns between 2009 and 2011. We develop a two-way coupler, the PeKing University CouPLer (PKUCPL), allowing for the exchange and interaction of chemical constituents between the global model (at 2.5˚ long. x 2˚ lat.) and the three nested models (at 0.667˚ long. x 0.5˚ lat.) covering Asia, North America, and Europe. The coupler obtains nested model results to modify the global model simulation within the respective nested domains, and simultaneously acquires global model results to provide lateral boundary conditions (LBCs) for the nested models.
Compared to the global model alone, the two-way coupled simulation results in enhanced CO concentrations in the nested domains. Sensitivity tests suggest the enhancement to be a result of improved representation of the spatial distributions of CO, nitrogen oxides, and non-methane volatile organic compounds, the meteorological dependence of natural emissions, and other resolution-dependent processes. The relatively long lifetime of CO allows for the enhancement to be accumulated and carried across the globe. We found that the two-way coupled simulation increased the global tropospheric mean CO concentrations in 2009 by 10.4 %, with a greater enhancement at 13.3 % in the Northern Hemisphere. Coincidently, the global tropospheric mean hydroxyl radical (OH) was reduced by 4.2 %, resulting in a 4.2 % enhancement in the methyl chloroform lifetime (MCF; via reaction with tropospheric OH). The resulting CO and OH contents and MCF lifetime are closer to observation-based estimates.
Both the global and the two-way coupled models capture the general spatiotemporal patterns of HIPPO CO over the Pacific. The two-way coupled simulation is much closer to HIPPO CO, with a mean bias of 1.1 ppb (1.4 %) below 9 km compared to the bias at 7.2 ppb (9.2 %) for the global model alone. The improvement is most apparent over the North Pacific. Our test simulations show that the global model alone could resemble the two-way coupled simulation (especially below 4 km) by increasing its global CO emissions by 15 % for HIPPO-1 and HIPPO-3, by 25 % for HIPPO-2 and HIPPO-4, and by 35 % for HIPPO-5. This has important implications for using the global model alone to constrain CO emissions. Thus, the two-way coupled simulation is a significantly improved model tool for studying the global impacts of air pollutants from major anthropogenic source regions.
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Influence of aerosols and surface reflectance on satellite NO2 retrieval: seasonal and spatial characteristics and implications for NOx emission constraints
Lin, J.-T. *, Liu, M.-Y., et al.
Atmospheric Chemistry and Physics, 15, 11217-11241, doi:10.5194/acp-15-11217-2015, 2015
Satellite retrievals of vertical column densities (VCDs) of tropospheric nitrogen dioxide (NO2) normally do not explicitly account for aerosol optical effects and surface reflectance anisotropy that vary with space and time. Here, we conduct an improved retrieval of NO2 VCDs over China, called the POMINO algorithm, based on measurements from the Ozone Monitoring Instrument (OMI), and we test the importance of a number of aerosol and surface reflectance treatments in this algorithm. POMINO uses a parallelized LIDORT-driven AMFv6 package to derive tropospheric air mass factors via pixel-specific radiative transfer calculations with no look-up tables, taking slant column densities from DOMINO v2. Prerequisite cloud optical properties are derived from a dedicated cloud retrieval process that is fully consistent with the main NO2 retrieval. Aerosol optical properties are taken from GEOS-Chem simulations constrained by MODIS AOD values. MODIS bi-directional reflectance distribution function (BRDF) data are used for surface reflectance over land. For the present analysis, POMINO level-2 data for 2012 are aggregated into monthly means on a 0.25 long. x 0.25 lat. grid.
POMINO-retrieved annual mean NO2 VCDs vary from 15–25 x 10^15 cm^-2 over the polluted North China Plain (NCP) to below 10^15 cm^-2 over much of west China. The subsequently-constrained Chinese annual anthropogenic emissions are 9.05 TgN yr^-1, an increase from 2006 (Lin, 2012) by about 19%. Replacing the MODIS BRDF data with the OMLER v1 monthly climatological albedo data affect NO2 VCDs by up to 40% for certain locations and seasons. The effect on constrained NOx emissions is small. Excluding aerosol information from the retrieval process (this is the traditional “implicit” treatment) enhances annual mean NO2 VCDs by 15–40% over much of east China. Seasonally, NO2 VCDs are reduced by 10–20% over parts of the NCP in spring and over north China in winter, despite the general enhancements in summer and fall. The effect on subsequently-constrained annual emissions is (-5)–(+30)% with large seasonal and spatial dependence. The implicit aerosol treatment also tends to exclude days with high pollution, a potentially important sampling bias. Therefore an explicit treatment of aerosols is important for space-based NO2 retrievals and emission constraints.
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Improved simulation of tropospheric ozone by a global-multi-regional two-way coupling model system
Yan, Y.-Y., Lin, J.-T. *, et al.
Atmospheric Chemistry and Physics, 16, 2381-2400, doi:10.5194/acp-16-2381-2016, 2016
Small-scale nonlinear chemical and physical processes
over pollution source regions affect the tropospheric
ozone (O3), but these processes are not captured by current
global chemical transport models (CTMs) and chemistry–
climate models that are limited by coarse horizontal resolutions
(100–500 km, typically 200 km). These models tend
to contain large (and mostly positive) tropospheric O3 biases
in the Northern Hemisphere. Here we use the recently built
two-way coupling system of the GEOS-Chem CTM to simulate
the regional and global tropospheric O3 in 2009. The
system couples the global model (at 2.5^N long.^B2^N lat.) and
its three nested models (at 0.667^N long.^B0.5^N lat.) covering
Asia, North America and Europe, respectively. Specifically,
the nested models take lateral boundary conditions (LBCs)
from the global model, better capture small-scale processes
and feed back to modify the global model simulation within
the nested domains, with a subsequent effect on their LBCs.
Compared to the global model alone, the two-way coupled
system better simulates the tropospheric O3 both within and
outside the nested domains, as found by evaluation against
a suite of ground (1420 sites from the World Data Centre
for Greenhouse Gases (WDCGG), the United States National
Oceanic and Atmospheric Administration (NOAA)
Earth System Research Laboratory Global Monitoring Division
(GMD), the Chemical Coordination Centre of European
Monitoring and Evaluation Programme (EMEP), and the
United States Environmental Protection Agency Air Quality
System (AQS)), aircraft (the High-performance Instrumented
Airborne Platform for Environmental Research (HIAPER)
Pole-to-Pole Observations (HIPPO) and Measurement
of Ozone and Water Vapor by Airbus In- Service Aircraft
(MOZAIC)) and satellite measurements (two Ozone
Monitoring Instrument (OMI) products). The two-way coupled
simulation enhances the correlation in day-to-day variation
of afternoon mean surface O3 with the ground measurements
from 0.53 to 0.68, and it reduces the mean model bias
from 10.8 to 6.7 ppb. Regionally, the coupled system reduces
the bias by 4.6 ppb over Europe, 3.9 ppb over North America
and 3.1 ppb over other regions. The two-way coupling
brings O3 vertical profiles much closer to the HIPPO (for remote
areas) and MOZAIC (for polluted regions) data, reducing
the tropospheric (0–9 km) mean bias by 3–10 ppb at most
MOZAIC sites and by 5.3 ppb for HIPPO profiles. The twoway
coupled simulation also reduces the global tropospheric
column ozone by 3.0DU (9.5 %, annual mean), bringing
them closer to the OMI data in all seasons. Additionally,
the two-way coupled simulation also reduces the global tropospheric
mean hydroxyl radical by 5% with improved estimates
of methyl chloroform and methane lifetimes. Simulation
improvements are more significant in the Northern
Hemisphere, and are mainly driven by improved representation
of spatial inhomogeneity in chemistry/emissions.
Within the nested domains, the two-way coupled simulation
reduces surface ozone biases relative to typical GEOSChem
one-way nested simulations, due to much improved
LBCs. The bias reduction is 1–7 times the bias reduction
from the global to the one-way nested simulation. Improving
model representations of small-scale processes is important
for understanding the global and regional tropospheric
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Global climate forcing of aerosols embodied in international trade
Lin, J.-T. *, et al.
Nature Geoscience, 9, 790-794, doi:10.1038/NGEO2798, 2016
International trade separates regions consuming goods and services from regions where goods and related aerosol pollution
are produced. Yet the role of trade in aerosol climate forcing attributed to di^[erent regions has never been quantified. Here,
we contrast the direct radiative forcing of aerosols related to regions’ consumption of goods and services against the forcing
due to emissions produced in each region. Aerosols assessed include black carbon, primary organic aerosol, and secondary
inorganic aerosols, including sulfate, nitrate and ammonium. We find that global aerosol radiative forcing due to emissions
produced in East Asia is much stronger than the forcing related to goods and services ultimately consumed in that region
because of its large net export of emissions-intensive goods. The opposite is true for net importers such as Western Europe
and North America: global radiative forcing related to consumption is much greater than the forcing due to emissions produced
in these regions. Overall, trade is associated with a shift of radiative forcing from net importing to net exporting regions.
Compared to greenhouse gases such as carbon dioxide, the short atmospheric lifetimes of aerosols cause large localized
di^[erences between consumption- and production-related radiative forcing. International e^[orts to reduce emissions in the
exporting countries will help alleviate trade-related climate and health impacts of aerosols while lowering global emissions.
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Rapid growth in nitrogen dioxide pollution over Western China, 2005–2013
Cui, Y.-Z., Lin, J.-T. *, et al.
Atmospheric Chemistry and Physics, 16, 6207-6221, doi:10.5194/acp-16-6207-2016, 2016
Western China has experienced rapid industrialization
and urbanization since the implementation of the
National Western Development Strategies (the “Go West”
movement) in 1999. This transition has affected the spatial
and temporal characteristics of nitrogen dioxide (NO2) pollution.
In this study, we analyze the trends and variability
of tropospheric NO2 vertical column densities (VCDs) from
2005 to 2013 over Western China, based on a wavelet analysis
on monthly mean NO2 data derived from the Ozone
Monitoring Instrument (OMI) measurements. We focus on
the anthropogenic NO2 by subtracting region-specific “background”
values dominated by natural sources. After removing
the background influences, we find significant anthropogenic
NO2 growth over Western China between 2005 and
2013 (8.6^F0.9%yr1 on average, relative to 2005), with
the largest increments (15%yr1 or more) over parts of several
city clusters. The NO2 pollution in most provinciallevel
regions rose rapidly from 2005 to 2011 but stabilized
or declined afterwards. The NO2 trends were driven mainly
by changes in anthropogenic emissions, as confirmed by
a nested GEOS-Chem model simulation and a comparison
with Chinese official emission statistics. The rate of NO2
growth during 2005–2013 reaches 11.3^F1.0%yr1 over
Northwestern China, exceeding the rates over Southwestern
China (5.9^F0.6%yr1) and the three well-known polluted
regions in the east (5.3^F0.8%yr1 over Beijing-Tianjin-
Hebei, 4.0^F0.6%yr1 over the Yangtze River Delta, and
3.3^F0.3%yr1 over the Pearl River Delta). Subsequent
socioeconomic analyses suggest that the rapid NO2 growth over Northwestern China is likely related to the fast developing
resource- and pollution-intensive industries along with
the “GoWest” movement as well as relatively weak emission
controls. Further efforts should be made to alleviate NOx pollution
to achieve sustainable development in Western China.
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Spatio-temporal variability of aerosols over East China inferred by merged visibility-GEOS-Chem aerosol optical depth
Lin, J.-T. *, Li, J.
Atmospheric Environment, 132, 111-122, doi:10.1016/j.atmosenv.2016.02.037, 2016
Long-term visibility measurements offer useful information for aerosol and climate change studies.
Recently, a new technique to converting visibility measurements to aerosol optical depth (AOD) has been
developed on a station-to-station basis (Lin et al., 2014). However, factors such as human observation
differences and local meteorological conditions often impair the spatial consistency of the visibility
converted AOD dataset. Here we further adopt AOD spatial information from a chemical transport model
GEOS-Chem, and merge visibility inferred and modeled early-afternoon AOD over East China on a 0.667^C
long. ^D 0.5^C lat. grid for 2005e2012. Comparisons with MODIS/Aqua retrieved AOD and subsequent
spectral decomposition analyses show that the merged dataset successfully corrects the low bias in the
model while preserving its spatial pattern, resulting in very good agreement with MODIS in both
magnitude and spatio-temporal variability. The low bias is reduced from 0.10 in GEOS-Chem AOD to 0.04
in the merged data averaged over East China, and the correlation in the seasonal and interannual variability
between MODIS and merged AOD is well above 0.75 for most regions. Comparisons between the
merged and AERONET data also show an overall small bias and high correlation. The merged dataset
reveals four major pollution hot spots in China, including the North China Plain, the Yangtze River Delta,
the Pearl River Delta and the Sichuan Basin, consistent with previous works. AOD peaks in springsummer
over the North China Plain and Yangtze River Delta and in spring over the Pearl River Delta,
with no distinct seasonal cycle over the Sichuan Basin. The merged AOD has the largest difference from
MODIS over the Sichuan Basin. We also discuss possible benefits of visibility based AOD data that correct
the sampling bias in MODIS retrievals related to cloud-free sampling and misclassified heavy haze
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Transboundary health impacts of transported global air pollution and international trade
Zhang, Q. *, Lin, J.-T. *, et al.
Nature, 543, 705-709, doi:10.1038/nature21712, 2017
Millions of people die every year from diseases caused by exposure
to outdoor air pollution. Some studies have estimated premature
mortality related to local sources of air pollution, but local air
quality can also be affected by atmospheric transport of pollution
from distant sources. International trade is contributing to the
globalization of emission and pollution as a result of the production
of goods (and their associated emissions) in one region for
consumption in another region. The effects of international
trade on air pollutant emissions, air quality and health have
been investigated regionally, but a combined, global assessment of
the health impacts related to international trade and the transport
of atmospheric air pollution is lacking. Here we combine four global
models to estimate premature mortality caused by fine particulate
matter (PM2.5) pollution as a result of atmospheric transport and
the production and consumption of goods and services in different
world regions. We find that, of the 3.45 million premature deaths
related to PM2.5 pollution in 2007 worldwide, about 12 per cent
(411,100 deaths) were related to air pollutants emitted in a region
of the world other than that in which the death occurred, and about
22 per cent (762,400 deaths) were associated with goods and services
produced in one region for consumption in another. For example,
PM2.5 pollution produced in China in 2007 is linked to more than
64,800 premature deaths in regions other than China, including
more than 3,100 premature deaths in western Europe and the USA;
on the other hand, consumption in western Europe and the USA is
linked to more than 108,600 premature deaths in China. Our results
reveal that the transboundary health impacts of PM2.5 pollution
associated with international trade are greater than those associated
with long-distance atmospheric pollutant transport.
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High natural nitric oxide emissions from lakes on Tibetan Plateau under rapid warming
Kong, H., Lin, J.-T. *, et al.
Nature Geoscience, doi:10.1038/s41561-023-01200-8, 2023
Nitrogen oxides affect health and climate. Their emissions, in the form of nitric oxide, from inland waters such as lakes are generally considered negligible and are absent in air quality and climate models. Here we find unexpected high emissions of nitric oxide from remote lakes on the Tibetan Plateau, based on satellite observations of tropospheric nitrogen dioxide vertical column densities and subsequent emission inversion at a fine resolution of 5 km. The total emissions from 135 lakes larger than 50 km2 reach 1.9 metric tons N h−1, comparable to anthropogenic emissions in individual megacities worldwide or the Tibet Autonomous Region. On average, the emissions per unit area reach 63.4 μg N m−2 h−1, exceeding those from crop fields. Such strong natural emissions from inland waters have not been reported, to the best of our knowledge. The emissions are derived from microbial processes in association with substantial warming and melting of glacier and permafrost on the plateau, constituting a previously unknown feedback between climate, lake ecology and nitrogen emissions.
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