Asian Dust Source Region Research Articles

Assessment of seasonal forecasting potential for springtime Asian dust in South Korea using the KMA global seasonal forecasting system

This study aims to assess the potential of seasonal forecasting for springtime Asian dust days in South Korea using the Korea Meteorological Administration's Global Seasonal Forecasting System version 6 (KMA GloSea6). The system demonstrated similar predictive performance for springtime Asian dust days compared to GloSea5-ADAM, which incorporates the Asian Dust and Aerosol Model's emission algorithm into GloSea5. While KMA GloSea6 exhibited strong wind, cold, and moist biases in the Asian dust source region during the spring of the hindcast period, similar to GloSea5-ADAM, it showed an improved spatial distribution of ACC. The anomaly correlation coefficient for the annual variability of Asian dust occurrence frequency anomalies in the dust source region was also similar, with values of 0.41 for KMA GloSea6 and 0.43 for GloSea5-ADAM. Furthermore, in evaluating the seasonal forecasting of springtime Asian dust days using hindcast datasets, KMA GloSea6 accurately predicted 12 out of 24 instances, resulting in a forecast accuracy of 0.5, consistent with GloSea5-ADAM. When applying the criteria to spring 2022 and 2023 forecast data not used in the derivation, the predicted Asian dust days of 6.14 days in spring 2022 led to a “Near normal” prediction, differing from the observed “Below normal.” However, the spatial distribution showed “Below normal” conditions, aligning with observations in some areas. In spring 2023, the predicted 9.78 Asian dust days led to an “Above normal” prediction, consistent with observed conditions. These findings will contribute to advancing seasonal Asian dust forecasting in South Korea.

Equatorial Pacific dust fertilization and source weathering influences on Eocene to Miocene global CO2 decline

Stimulation of the biological pump by iron-bearing dust in the eastern equatorial Pacific Ocean plays an important role in long-term carbon sequestration, yet past dust fertilization and its impact on CO2 perturbations over major climate transitions remain debated. Here, we integrate proxies of dust input, source-region weathering, and biological pump activity from late Eocene to early Miocene sediments of Integrated Ocean Discovery Program Hole U1333, which includes the Eocene-Oligocene Transition (~34 million years ago) when a major ice sheet was first established on Antarctica. We find that intensified chemical weathering in the large central Asian dust source region enhanced atmospheric CO2 removal at ~34 Ma. Superimposed dust fertilization and biological pump action amplified this CO2 removal before ~34 Ma, while weakening of this amplification process helped to moderate the CO2 decline after that time. The observed inter-linked, counteracting processes with different timescales illustrate the complexity of carbon cycle feedbacks associated with major climate changes.

Modeling a severe wintertime Asian dust event observed in the East Asia region: Sensitivity of the WRF-Chem dust emission schemes

This study investigates the capability of the Weather Research and Forecasting-Chemistry (WRF-Chem) model in modeling a severe wintertime Asian dust event, which originated from the East Asia dust source region during 20–22 February 2015. The WRF-Chem simulations were conducted changing with the five embedded dust emission schemes of the UC01, UC04, UC11, GO01, and GA19 schemes. The model reasonably simulated meteorological fields, capturing the characteristic meteorological features over the dust source regions during the severe wintertime Asian dust event. A good meteorological comparison led to the reasonable simulation of the occurrence and transport of the Asian dust plumes, comparing well with the surface dust occurrence reports and the satellite-detected dust signals of aerosol optical depth (AOD) and extinction coefficient. However, considerable (approximately fivefold) differences existed in the dust emission amounts simulated by the different dust emission schemes. From the model-measurement comparison of surface PM10 concentration, it was found that the UC01 and UC04 schemes could simulate the severe wintertime Asian dust plumes in the dust source regions, capturing the dust occurrence timing and the concentration level reasonably. However, the performance of the schemes significantly depended on near-surface wind speed and soil moisture amount. On the contrary, the UC11, GO01, and GA19 schemes failed to simulate the dust plumes, revealing intrinsic limitations for severe wintertime dust plume simulation. Furthermore, this study suggests the realistic representation of the Asian dust source region and the inclusion of frozen soil parameterization in the WRF-Chem model to predict severe wintertime Asian dust events realistically.

Interannual changes of land surface conditions in Asian dust source regions since 2000

Interannual changes of land surface conditions in Asian dust source regions since 2000

Long-range transport of airborne bacteria over East Asia: Asian dust events carry potentially nontuberculous Mycobacterium populations.

The nontuberculous mycobacterial pulmonary disease (NTM-PD) caused by Mycobacterium species has increased in prevalence all over the world. The distributions of NTM-PD are possibly determined by the westerly wind traveling at high altitudes over East Asia. However, the long-range transport of Mycobacterium species has not been demonstrated by analyzing the bacterial communities in aerosols such as desert mineral particles and anthropogenic pollutants transported by the westerly wind. Here, airborne bacterial compositions were investigated including Mycobacterium species in high-elevation aerosols, which were captured in the snow cover at 2,450m altitude on Mt. Tateyama. This was further compared to the ground-level or high-altitude aerosols collected at six sampling sites distributed from Asian-dust source region (Tsogt-Ovoo) to downwind areas in East Asia (Asian continental cities; Erenhot, Beijing, Yongin, Japanese cities; Yonago, Suzu, Noto Peninsula). The cell concentrations and taxonomic diversities of airborne bacteria decreased from the Asian continent to the Japan area. Terrestrial bacterial populations belonging to Firmicutes and Actinobacteria showed higher relative abundance at high-elevation and Japanese cities. Additionally, Mycobacterium species captured in the snow cover on Mt. Tateyama increased in relative abundance in correspondence to the increase of black carbon concentrations. The relative abundance of Mycobacterium sequences was higher in the aerosol samples of Asian continental cities and Japanese cities than in the desert area. Presumably, anthropogenic pollution over East Asia carries potential Mycobacterium species, which induce NTM-PD, thereby impacting upon the public health.

Climatology of Dust Aerosols over the Jianghan Plain Revealed with Space-Borne Instruments and MERRA-2 Reanalysis Data during 2006–2021

In recent years, climate change and the intervention of anthropogenic activities have altered the seasonal features of Asian dust storms. This may also cause seasonal variations (including dust occurrence frequency and optical/microphysical properties) in dust aerosols transported to downstream regions. The Jianghan Plain is dramatically influenced by multiple dust sources due to its geographical location in central China. In this study, we focused on the climatology of dust aerosols over the Jianghan Plain based on the 15-year (2006–2021) continuous space-borne observations of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) as well as Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) reanalysis data. A typical dust event that intrudes the Jianghan Plain was studied in detail. According to the statistical results, dust aerosols frequently intrude into the Jianghan Plain in spring and winter, with occurrence frequencies (under cloud free condition hereafter) exceeding 0.70 and higher altitudes of 4–6 km. The dust occurrence frequency declined to approximately 0.40 in autumn and nearly zero in summer, while the dust plumes were generally located at lower altitudes of 1–3 km. The dust plumes observed in the Jianghan Plain were simultaneously linked to the Taklimakan Desert and Gobi Desert in spring and mainly originated from the Taklimakan Desert in winter and autumn. The dust particles were mainly distributed below 4-km altitude, with the largest dust extinction coefficients and dust mass concentrations in spring. In all seasons, the particle depolarization ratios are 0.1–0.2 below 4-km altitude, suggesting a possible mix with local anthropogenic aerosols. The mean dust column mass concentrations in spring showed an evident declining trend from 210 µg m−2 in 2006 to 100 µg m−2 in 2021 in the Jianghan Plain, attributed to the reduced dust activity in the source regions of Asian dust.

Evaluating the Meteorological Conditions Associated With Dusty Atmospheric Rivers

AbstractTrans‐Pacific dust has been shown to influence the micro‐physical characteristics of atmospheric rivers that make landfall along the U.S. west coast. Atmospheric Rivers (AR) reaching North America provide valuable water resources, but also can produce damaging floods. While substantial research has been devoted to understanding the structure and meteorological drivers of atmospheric rivers, far less is known about the conditions that lead to the presence of dust within and around these storms. Here, we utilize an 18‐year record of the dust content of AR surroundings combined with satellite, reanalysis, and observational meteorological data to understand the drivers of ARs embedded within dusty environments, or “dusty ARs,” as compared to ARs in more pristine environments. We find that dusty ARs are associated with transport of dust from the east Asian coast to North America. Dusty ARs are characterized by conditions that are especially conducive to transport of dust across the Pacific; namely, enhanced mid‐ to upper‐tropospheric westerly winds over Asian dust source regions and over the Pacific. In contrast, ARs in more pristine environments are associated with a persistent ridge over the central Pacific, which blocks zonal westerly flow, as well as continental dust. We also show that while trans‐Pacific dust is largely confined to the 600–200 hPa levels, this dust flows downward along post‐cold frontal isentropic surfaces into the AR environment in the lower troposphere.

Retrievals of dust-related particle mass and ice-nucleating particle concentration profiles with ground-based polarization lidar and sun photometer over a megacity in central China

Abstract. The POLIPHON (polarization lidar photometer networking) method is a powerful pathway to retrieve the height profiles of dust-related particle mass and ice-nucleating particle (INP) concentrations. The conversion factors fitted from the sun photometer observation data are the major part of the POLIPHON computations, which can convert the polarization-lidar-derived dust extinction coefficients into dust-related particle mass and INP concentrations. For the central Chinese megacity of Wuhan (30.5∘ N, 114.4∘ E), located at the downstream area several thousands of kilometers far away from the source regions of Asian dust, dust particles always mix with other aerosols from local emissions. Therefore, very few dust case data sets can be available when using the column-integrated Ångström exponent (for 440–870 nm) <0.3 and aerosol optical depth (at 532 nm) >0.1 recorded by a sun photometer as the filtering criteria. Instead, we present another dust case data set screening scheme that applies the simultaneous polarization lidar observation to verify the occurrence of dust. Based on the 33 dust-intrusion days identified during 2011–2013, the extinction-to-volume (cv,d) and extinction-to-large particle (with radius >250 nm) number concentration (c250,d) conversion factors are determined to be (0.52±0.12)×10-12Mmm3m-3 and 0.19±0.05 Mm cm−3, respectively. The c250,d for Wuhan is 27 % larger than that observed at Lanzhou SACOL (36.0∘ N, 104.1∘ E), a site closer to the Gobi Desert, and tends to be closer to those observed in North Africa and the Middle East, indicating dust aerosols from these two sources are also possibly involved in the dust events observed over Wuhan. As a comparison, the conversion factor c290,c of 0.11±0.02Mmcm-3 for continental aerosol is much smaller than c250,d, indicating that there is no significant influence of urban aerosols on the retrievals of dust-related conversion factor over Wuhan. The conversion factors are applied in a dust event in Wuhan to reveal the typical dust-related immersion-mode INP concentration over East Asian cities. The proposed dust case data set screening scheme may potentially be extended to the other polluted city sites that are more influenced by mixed dust.

Improvements of ADAM3 by Incorporating New Dust Emission Reduction Formulations Based on Real-Time MODIS NDVI

Dust events in Northeast Asia have several adverse effects on human health, agricultural land, infrastructure, and transport. Wind speed is the most important factor in determining the total dust emission at the land surface; however, various land-surface conditions must be considered as well. Recently, the Korea Meteorological Administration updated the dust emission reduction factor (RF) in the Asian Dust Aerosol Model 3 (ADAM3) using data from the normalized difference vegetation index (NDVI) of the Moderate Resolution Imaging Spectroradiometer (MODIS). We evaluated the improvements of ADAM3 according to soil types. We incorporated new RF formulations in the evaluation based on real-time MODIS NDVI data obtained over the Asian dust source regions in northern China during spring 2017. This incorporation improved the simulation performance of ADAM3 for the PM10 mass concentration in Inner Mongolia and Manchuria for all soil types, except Gobi. The ADAM3 skill scores for sand, loess, and mixed types in a 24 h forecast increased by 6.6%, 20.4%, and 13.3%, respectively, compared with those in forecasts employing the monthly RF based on the NDVI data. As surface conditions in the dust source regions continually change, incorporating real-time vegetation data is critical to improving performance of dust forecast models such as ADAM3.

Lithium isotopic features of Quaternary basaltic saprolite, Zhanjiang, China: Atmospheric input and clay-mineral adsorption

Silicate weathering, in particular basalt, accounting only for one-sixth of the continental crust volume, accounts for one-third of atmospheric CO2 drawn down during weathering, as such, playing an important role in long-term carbon cycling. Li contents and isotopic compositions of a tropical regolith developed on young basalt (ca. 1 Ma) were investigated to elucidate Li isotopic fractionation during basalt weathering so as to trace basalt weathering. Li isotopic composition of sand from Asian dust-source regions and local dust near the basaltic saprolite weathering profile were studied as possible atmospheric contributors of Li to the saprolite. Saprolite has δ7Li values of −6.8‰ to −2.2‰, which is much lighter than that of fresh basalt (+3.5‰). Approximately 30% of the Li was lost from the upper saprolite profile, without significant isotopic fractionation. Lithium is enriched at the bottom of the profile, showing the lightest Li isotopic composition (δ7Li = −6.6‰ to −2.6‰). Calculations indicates that marine aerosols are the main source of atmospheric Li input to the profile. Adsorption of Li by secondary minerals results Li isotopic fractionation, accompanying desorption and resorption of Li by secondary minerals, resulting enriched Li and light Li isotopic composition in the regolith. A model established that Li isotopes showed sensitivity to continental weathering, supporting that Li isotopes can serve as an indicator of continental weathering. Continental weathering in the study area recorded the reasons of heavier Li isotopic composition of river water and seawater suggesting that Li isotopes can be used to study the circulation of materials on the Earth's surface. This has a guiding role in studying the Li isotopic composition of shale and rivers. The influence of temperature and precipitation on the fractionation behavior of lithium isotopes during silicate weathering warrants further investigation.

Identifying the dominant local factors of 2000–2019 changes in dust loading over East Asia

East Asian dust aerosols play a vital role in the local and regional climate through its direct, indirect, and semidirect effects, but the dominant factors affecting the interannual variation of dust aerosols over East Asia and their regional differences remain unclear. This study verified the accuracy of MEERA-2 dust data in East Asia, analyzed the interannual trends of dust in East Asia from 2000 to 2019 using the MERRA-2 dust column mass density (DCMD) and identified the dominant factors affecting the interannual variation during the dusty season (March–July) by developing the regional multiple linear regression models, combined with correlation and partial correlation analysis. The comparison with the dust index (DI) calculated from ground-based observations of dust events frequency indicated that MERRA-2 DCMD exhibited high spatial agreement ( R > 0.8) with ground-based observations in most regions (especially in the dust source region of North China). The trend analysis revealed that DCMD in East Asia decreased significantly after 2000, particularly in the dusty season (March–July). These significant decreases were generally highly correlated with increases in normalized differential vegetation index (NDVI), volumetric soil moisture (VSM), and precipitation (PPT) and with decreases in wind speed (WS). Furthermore, WS dominated the interannual variation in the dust concentration over the East Asian dust source regions and their downstream. By contrast, PPT, through its wet deposition effect, dominated the variation in the rest of the regions away from the dust source regions. The study findings may help clarify the associations between local meteorological and surface factors and long-term variations in dust aerosols over East Asia. • MERRA-2 DCMD has a high accuracy in East Asia in 2000-2018. • Significant increases in NDVI, SM and PPT and significant decrease in WS all contributed to the decrease in DCMD. • WS dominated the variation of dust over the East Asian dust source regions and their downstream. • PPT dominated the variation of dust in the rest of the regions away from the dust source regions.

Modulation of springtime surface sensible heating over the Tibetan Plateau on the interannual variability of East Asian dust cycle

Abstract. Previous observational evidence and numerical simulations have revealed that the surface sensible heating in spring (March–April–May, MAM) over the Tibetan Plateau (TPSH) can affect the Asian regional hydrological cycle, surface energy balance, and climate through altering atmospheric heat source of the Tibetan Plateau (TP). This study aims to investigate the impacts of MAM TPSH on the interannual variability of East Asian dust cycle by using CAM4-BAM (version 4 of the Community Atmosphere Model coupled to a bulk aerosol model), MERRA-2 (version 2 of the Modern-Era Retrospective analysis for Research and Applications) surface dust concentration, and TPSH measurements. Our simulations show that the surface dust concentrations over the East Asian (EA) dust source region and over the northwestern Pacific (NP) in MAM are significantly positively correlated with TPSH, with regionally averaged correlation coefficients of 0.49 for EA and 0.44 for NP. Similar positive correlations are also shown between the MAM TPSH measurements averaged over the 73 observation sites and the surface dust concentration from MERRA-2. Simulation-based comparisons between strongest and weakest TPSH years reveal that, the MAM surface dust concentration in the strongest TPSH years increases with relative differences of 13.1 % over EA and 36.9 % over NP. These corresponding differences are found in MERRA-2 with 22.9 % and 13.3 % over EA and NP, respectively. Further simulated results show that the processes of whole dust cycles (e.g., dust loading, emission, and transport, as well as dust deposition) are also significantly enhanced during the strongest TPSH years over EA and NP. Through enhancing the TP heat source, stronger TPSH in MAM generates an anticyclonic anomaly in middle and upper troposphere over the TP and over the downstream Pacific region, respectively. These atmospheric circulation anomalies induced by the increased TPSH result in increasing the westerly winds over both EA and NP, which in turn increases dust emissions over the dust source, and dust transport over these two regions, as well as the regional dust cycles. These results suggest that addressing the East Asian dust changes in the future climates requires considering not only increasing greenhouse gas emissions but also the variations of the TP's heat source under global warming.

Effects of dust-in-snow forcing over the Tibetan Plateau on the East Asian dust cycle during the Last Glacial Maximum

The improved Community Atmosphere Model version 4 with a Bulk Aerosol Model parameterizations of the dust size distribution (CAM4-BAM) was used to investigate the dust-in-snow radiative forcing (SRF) over the Tibetan Plateau (TP) and its feedbacks on the regional climate and the dust cycle in spring, the season with the strongest dust activity, over East Asia during the Last Glacial Maximum (LGM). Simulated results show that the dust in snow can cause a large positive SRF and significant warming at the TP surface, reaching more than 45 W m−2 and 3–5 °C warming in western TP during the LGM. The SRF increases the East Asian dust emissions, dry deposition and wet deposition by 71.6 Tg (8.1%), 34.5 Tg (7.0%) and 7.9 Tg (16.0%), respectively, in spring during LGM. Further analysis reveals that, the SRF warms the TP surface and enhances the thermal effect of the TP in spring by increasing the surface shortwave radiative forcing, sensible and latent heat fluxes. A mid-upper level anticyclonic circulation anomaly is generated, thus increases the regional westerly wind over the East Asian dust source region, and in turn enhances the dust emission and dust transport over East Asia. In general, SRF over the TP creates a positive feedback loop of enhancing the East Asian dust cycle during LGM.

The Reduction of the Global Irradiance Due to the Asian Dust Aerosols (PM10) Estimated by the Observed Data in the Dust Source Region of Erdene in Mongolia

An empirical method of the PM10 to reduce the global irradiance has been developed with the observed 14-day data in 2009 at the Erdene site in the Asian dust source region of Mongolia. The observed data at a 10-min interval are used to get all parameters for the estimation of the beam and diffuse irradiances except for the properties of Asian dust aerosols such as the single scattering albedo (ω0), scattering transmittance (τa) and transmittance due to aerosol absorption (τaa) using the parametric solar radiation model. To determine these parameters, firstly τa is calculated with the observed global irradiance for a given ω0 value using all sampled data. And then the estimated τas are correlated with observed dust concentration to find an optimal regression equation between τa and the observed dust concentration. The optimal ω0 value is found that the error between the calculated global irradiance using the optimal regression equation and the observed global irradiance becomes minimum. It is found that the single scattering albedo of Asian dust aerosol (ω0) is 0.85 and its reduction rate of the global irradiance is up 34.4% of that of the dust free atmosphere for the heavy dust case. This reduction is mainly contributed by the reduction of the beam irradiance whereas the diffuse irradiance enhances slightly (about 1.8%) the global irradiance. The presently developed optimal regression equation between τa and the observed dust concentration has a great potential to estimate the impact of Asian dust aerosols on the solar irradiance.

Radiative feedbacks of dust in snow over eastern Asia in CAM4-BAM

Abstract. Dust in snow on the Tibetan Plateau (TP) could reduce the visible snow albedo by changing surface optical properties and removing the snow cover through increased snowmelt, which leads to a significant positive radiative forcing and remarkably alters the regional energy balance and the eastern Asian climate system. This study extends our previous investigation in dust–radiation interactions to investigate the dust-in-snow radiative forcing (SRF) and its feedbacks on the regional climate and the dust cycle over eastern Asia through the use of the Community Atmosphere Model version 4 with a Bulk Aerosol Model parameterizations of the dust size distribution (CAM4-BAM). Our results show that SRF increases the eastern Asian dust emissions significantly by 13.7 % in the spring, countering a 7.6 % decrease in the regional emissions by the dust direct radiative forcing (DRF). SRF also remarkably affects the whole dust cycle, including transport and deposition of dust aerosols over eastern Asia. The simulations indicate an increase in dust emissions of 5.1 %, due to the combined effect of DRF and SRF. Further analysis reveals that these results are mainly due to the regional climatic feedbacks induced by SRF over eastern Asia. By reducing the snow albedo over the TP, the dust in snow mainly warms the TP and influences its thermal effects by increasing the surface sensible and latent heat flux, which in turn increases the aridity and westerly winds over northwestern China and affects the regional dust cycle. Additionally, the dust in snow also accelerates the snow-melting process, reduces the snow cover and then expands the eastern Asian dust source region, which results in increasing the regional dust emissions. Hence, a significant feature of SRF on the TP is the creation of a positive feedback loop that affects the dust cycle over eastern Asia.

Decoupling of Climatic Drying and Asian Dust Export During the Holocene

AbstractBoth paleoclimatic records and models suggest that the dust accumulation in ice cores and marine sediments, which is often regarded as a direct record of changing atmospheric dust loading and used to estimate its climatic impact, is strongly coupled to the aridity of dust source regions. However, the underlying association of this couple has not been tested directly because of the lack of continuous and well‐dated independent records of eolian activity in dust source regions. Here we present a high‐resolution multiproxy record of the Holocene eolian activity and climate changes from Lake Xiarinur in north China, a major Asian dust source region. Our data, together with the records of Asian dust accumulation in downwind areas, including the North Pacific Ocean and Greenland, suggest a decoupling between long‐distant Asian dust export and climatic drying in the Holocene. Although the climate was humid and the eolian activity was weak in the source region during the early Holocene, the dust accumulation in the North Pacific Ocean and Greenland was relatively high. Similarly, while climatic drying and strong eolian activity occurred in north China during the late Holocene, the rate of dust accumulation in the downwind areas was low. The long‐distant export of Asian dust is closely correlated with the strength of the Siberian High rather than the westerlies as widely believed before. The rate of dust accumulation in the GISP2 Greenland ice core is comparable in patterns with the intensity of the Siberian High forced eolian activity on both millennial and centennial time scales.

Effects of Asian dust events on atmospheric bacterial communities at different distances downwind of the source region

Aeolian dust particles arising from arid and semiarid zones are known to carry microbes by air currents. The effect of wind-borne bacteria on atmospheric bacterial population at various downwind distances from the dust source regions must be clarified, but has not yet been reported. This study monitored the bacterial abundance and community composition in outdoor aerosol samples in Beijing, China, which is close to the Asian dust source regions, and compared them with the results obtained in a distant region (Osaka, Japan). The Asian dust collected in Beijing contained (4±3)×104bacterial cells/m3, approximately 4 times higher than in Osaka. On 15 April 2015, Beijing experienced severe Asian dust events with a 1000-fold increase in bacterial abundance, relative to non-Asian dust days. Dominant bacterial phyla and classes in Asian dust collected in Beijing were Actinobacteria, Bacilli and Acidobacteria, and the bacterial community composition varied more widely than in Osaka. The bacterial community compositions differed between the Beijing and Osaka dusts, even for the same Asian dust events. These results indicated that aerosol bacterial communities nearer the dust source are more affected by eolian dust than their distant counterparts.

A lacustrine record of East Asian summer monsoon and atmospheric dust loading since the last interglaciation from Lake Xingkai, northeast China

AbstractA 336-cm-long sediment core spanning the last 130 ka was recovered from Lake Xingkai on the northeastern margin of the East Asian summer monsoon domain to reveal the linkage between lacustrine depositional processes and environmental changes. Bayesian end member modeling analysis was conducted to partition and interpret the grain-size distributions of Lake Xingkai sediments. Our results suggest that the sedimentary system is characterized by three end members (EMs). EM1 and EM2, with a modal value of 13 and 10 μm, respectively, indicate the variation of local hydraulic conditions. EM3, with a modal value of 5 μm, reflects the background atmospheric dust loading. High atmospheric dust concentration generally occurred during Marine Isotope Stage (MIS) 5d, MIS 4, and early MIS 3, when the climate in the Asian dust source region was cold and dry. In contrast, low dust concentration prevailed during MIS 2, likely due to the southward shift of the westerlies driven by maximum ice volume in the high latitudes.

Variations of Ozone and PM10 Concentrations and Meteorological Conditions according to Airflow Patterns of their High Concentration Episodes on Jeju Island

The classification of airflow patterns during high ozone (O3) and PM10 episodes on Jeju Island in recent years (2009-2015), as well as their correlation with meteorological conditions according to classified airflow patterns were investigated in this study. The airflow patterns for O3 and PM10 were classified into four types (Types A-D) and three types (Types E-G), respectively, using the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and synoptic weather charts. Type A was the most dominant airflow pattern for O3 episodes, being characterized by the transport of airflows from urban and industrial areas in China with the highest frequency (about 69%, with a mean of 67 ppb). With regard to the PM10 episodes, Type E was the most dominant airflow pattern, and was mostly associated with long distance transport from Asian dust source regions along northwesterly winds, having the highest frequency (about 92%, with a mean of 136 μg/m3). The variations in the concentration of O3 and PM10 during the study period were clarified in correlation with two pollutant and meteorological variables; for example, the high (low) O3 and PM10 concentrations with high (low) air temperature and/or wind speed and vice versa for precipitation. The contribution of long-range transport to the observed PM10 levels in urban sites for different airflow patterns (Types E-F), if estimated in comparison to the data from the Gosan background site, was found to account for approximately 87-93% (on average) of its input. The overall results of the present study suggest that the variations in O3 and PM10 concentrations on Jeju Island are mainly influenced by the transport effect, as well as the contribution of local emissions. emissions.

A Typical Formation Mechanism of Heavy Haze-Fog Induced by Coal Combustion in an Inland City in North-Western China

ABSTRACTPM2.5, TSP, and the pollutant gases over Urumqi, an inland city near the Asian dust source region in north-western China, were measured for an entire year from March, 2008 to February, 2009. The chemical compositions of all these samples with daily visibilities were investigated for the sources and formation mechanisms of aerosol and the relationship of the optical property with various components in aerosols. The sources of the air pollutants that caused severe haze in Urumqi were clarified. It was found that the concentrations of SO42–, Cl–, NH4+, and Na+ in PM2.5 in the heating period were more than 9 times of those in the non-heating period. The concentrations of total water soluble inorganic ions (TWSII) in PM2.5 and TSP in the heating period were 7.5 and 5.5 times of those in the non-heating period. The enrichment factors of the pollution elements, e.g., S, Cd, As, Zn, Pb, Cu, Cr, and Na in PM2.5 in the heating period were 3–13 times of those in the non-heating period. The formation mechanism of the severe haze and the micro-mechanism of the visibility reduction in Urumqi in the heating period, especially in winter, were quantitatively revealed. SNA (the three secondary inorganic ions, SO42–, NO3–, and NH4+), organic matter (OM), and chloride (Cl–) in PM2.5 were the three main components to cause aerosol extinction in Urumqi. The contributions of SNA, OM, and Cl– to aerosol extinction, i.e., to visibility reduction, were 57%, 20%, and 12% during the heating period from October 15 to April 15, and 67%, 17%, and 12% in winter, respectively. It was evident that the major source of the air pollutants that caused severe haze in Urumqi was from coal combustion, for most of these ions and pollution elements in aerosols were emitted from coal burning. The control of the quality and quantity of coal burning is the key to improve the air quality and the atmospheric visibility in Urumqi.