Previous studies have reported boundary layer features related to air pollution. However, few studies have comprehensively evaluated the characteristics and mechanisms of vertical wind in the formation and evolution of heavy particulate matter pollution episodes (EP) in Hong Kong. In this study, we analyzed the vertical characteristics of heavy particulate matter (PM) pollutions over Hong Kong and their relationships with vertical wind profiles using high‐time‐resolution Doppler lidar measurements and hourly meteorological and air quality observations. We identified nine EPs and show that the events were closely coupled to various vertical wind profiles in the planetary boundary layer (PBL). Our analysis suggests that strong vertical wind speed with wind shear at certain heights in the PBL had a positive correlation with surface PM during most superregional transboundary EPs. The maximum transport height extends from the surface to about 2.0 km or even higher; these transport heights differed among superregional and regional transboundary EPs. At peak surface pollution concentrations during the nine EPs, the surface PM10 had a significant negative correlation with PBL heights/mixing layer heights, while the averaged wind shear in the PBL was significantly positively correlated. These EPs with different mixing layer heights were mainly driven by different vertical wind shear conditions under various weather systems related to surface high pressure, cold fronts, dust storms, and typhoons. This work provides scientific evidence that surface PM pollutions were closely related to the characteristics of vertical profiles during the transboundary air pollutions.
Abstract. The planetary boundary layer (PBL) governs the vertical transport of mass,
momentum, and moisture between the surface and the free atmosphere, and thus
the determination of PBL height (BLH) is recognized as crucial for air
quality, weather, and climate analysis. Although reanalysis products can
provide important insight into the global view of BLH in a seamless way, the BLH observed in situ on a global scale remains poorly understood due to the lack of
high-resolution (1 or 2 s) radiosonde measurements. The present study
attempts to establish a near-global BLH climatology at synoptic times (00:00
and 12:00 UTC) and in the daytime using high-resolution radiosonde
measurements over 300 radiosonde sites worldwide for the period 2012 to
2019, which is then compared against the BLHs obtained from four reanalysis
datasets, including ERA5, MERRA-2, JRA-55, and NCEP-2. The variations in
daytime BLH exhibit large spatial and temporal dependence, and as a result
the BLH maxima are generally discerned over the regions such as the western
United States and western China, in which the balloon launch times mostly
correspond to the afternoon. The diurnal variations in BLH are revealed with
a peak at 17:00 local solar time (LST). The most promising reanalysis product
is ERA5, which underestimates BLH by around 130 m as compared to radiosondes
released during daytime. In addition, MERRA-2 is a well-established product
and has an underestimation of around 160 m. JRA-55 and NCEP-2 might produce
considerable additional uncertainties, with a much larger underestimation of
up to 400 m. The largest bias in the reanalysis data appears over the
western United States and western China, and it might be attributed to the
maximal BLH in the afternoon when the PBL has risen. Statistical analyses
further indicate that the biases of reanalysis BLH products are positively
associated with orographic complexity, as well as the occurrence of static
instability. To our best knowledge, this study presents the first
near-global view of high-resolution radiosonde-derived boundary layer height
and provides a quantitative assessment of the four frequently used
reanalysis products.
The United Nations has reported that 55% of the global population resides in urban areas, and 68% of the population is expected to be urban dwellers by 2050. Urbanization has critical implications for global land cover. Relevant literature has provided evidence attributing climatic effects to urban expansion; however, few studies have investigated the effect on public health and pollutant sensitivity to emissions. This study aimed to characterize the effect of urbanization‐induced changes in regional climate on ozone (O3), to evaluate ozone sensitivity to nitrogen oxide (NOx) and volatile organic compound (VOC) emissions, and to estimate premature mortalities due to O3 exposure. We employed atmospheric models with the higher‐order decoupled direct method to simulate effects of urbanization on O3 and to determine O3 sensitivity to NOx and VOC emissions. China‐specific concentration response functions were utilized to estimate cardiovascular and respiratory mortalities due to ozone exposure. Urbanization increased O3, which translated to a 39.6% increase in O3‐induced premature mortality (1,100 deaths). Moreover, O3 has become less/more sensitive to unit changes in NOx and VOC emissions in various cities. Urban greening may reduce urban temperature, but it may increase O3 in some cities due to the additional VOC emissions of greening. These findings highlight the strong interactions between land use policies, urban climate adaptation strategies, and air quality policies, suggesting the need of cobeneficial strategies and policies. We proposed a precision environmental management concept that emphasizes the importance of considering the specific atmospheric condition and composition of a city when formulating its environmental policies.
This cross-sectional study evaluates the association of air pollution exposure and having been breastfed or not with lung function among children in China.
Abstract. Numerous studies have reported that ambient air pollution, which has both
local and long-range sources, causes adverse impacts on the environment and
human health. Previous studies have investigated the impacts of
transboundary air pollution (TAP) in East Asia, albeit primarily through
analyses of episodic events. In addition, it is useful to better understand
the spatiotemporal variations in TAP and the resultant impact on the
environment and human health. This study aimed at assessing and
quantifying the air quality impacts in Japan and South Korea due to local emissions and TAP from sources in East Asia - one of the most polluted
regions in the world. We applied state-of-the-science atmospheric
models to simulate air quality in East Asia and then analyzed the air
quality and acid deposition impacts of both local emissions and TAP sources
in Japan and South Korea. Our results show that ∼ 30 % of
the annual average ambient PM2.5 concentrations in Japan and South
Korea in 2010 were contributed to by local emissions within each country, while
the remaining ∼ 70 % were contributed to by TAP from other
countries in the region. More detailed analyses also revealed that the local
contribution was higher in the metropolises of Japan (∼ 40 %–79 %) and South Korea (∼ 31 %–55 %) and that minimal
seasonal variations in surface PM2.5 occurred in Japan, whereas there was a
relatively large variation in South Korea in the winter. Further, among all
five studied anthropogenic emission sectors of China, the industrial sector
represented the greatest contributor to annual surface PM2.5
concentrations in Japan and South Korea, followed by the residential and
power generation sectors. Results also show that TAP's impact on acid
deposition (SO42- and NO3-) was larger than TAP's impact
on PM2.5 concentrations (accounting for over 80 % of the total
deposition), and that seasonal variations in acid deposition were similar
for both Japan and South Korea (i.e., higher in both the winter and summer).
Finally, wet deposition had a greater impact on mixed forests in Japan and
savannas in South Korea. Given these significant impacts of TAP in the
region, it is paramount that cross-national efforts should be taken to mitigate air
pollution problems across East Asia.
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