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[Display omitted] The Hunga Tonga-Hunga Ha'apai eruption on January 15, 2022 was one of the most explosive volcanic eruptions of the 21st century and has attracted global attention. Here we show that large numbers of the volcanic aerosols from the eruption broke through the tropopause into the lower stratosphere, forming an ash plume with an overshooting top at 25–30 km altitude. In the four days following the eruption, the ash plume moved rapidly westward for nearly 10,000 km under stable stratospheric conditions characterized by strong tropical easterlies, weak meridional winds and weak vertical motion. The intrusion of the ash plume into the stratosphere resulted in a marked increase in atmospheric aerosol loading across northern Australia, with the aerosol optical depth (AOD) observed by satellites and sun-photometers peaking at 1.5 off the coast of northeastern Australia; these effects lasted for nearly three days. The ash plume was characterized by fine-mode particles clustered at a radius of about 0.26 µm, with an observed peak volume of 0.25 µm3 µm−2. The impact of the ash plume associated with the Hunga Tonga eruption on the stratospheric AOD and radiative balance in the tropical southern hemisphere is remarkable, with an observed volcanic-induced perturbation of the regional stratospheric AOD of up to 0.6. This perturbation largely explains an instantaneous bottom (top) of the atmosphere radiative forcing of −105.0 (−65.0) W m−2 on a regional scale. [ABSTRACT FROM AUTHOR]

Springtime smoke aerosols attributable to biomass burning on the Indochina Peninsula (ICP) are a major source of absorbing aerosols globally, and play a nonnegligible perturbing role in climate change. Using smoke extinction profiles provided by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument, and aerosol and meteorological reanalyses for the period 2007–2021, this study investigated the three-dimensional structure and transport flux of springtime smoke aerosols over the ICP. Stratified analysis revealed that CALIOP-derived peaks of smoke aerosol optical depth (SAOD) and smoke mass flux (SMF) at altitudes of 0–2 km occur over the central ICP, which is the main source region. Driven by a southwesterly jet stream and updrafts, massive amounts of smoke aerosols are transported toward the northeast of the ICP, resulting in the largest stratified SAOD and SMF observed at altitudes of 2–4 km. Over the main smoke source regions, the estimated springtime SMF was approximately 0.4 Tg accumulated through a distance of 2° latitude at altitudes of 2–4 km. Meteorological analyses indicated a path for the transport of smoke aerosols to the mid-troposphere. Smoke aerosols in the source region are first lifted thermally to the 600-hPa level. Lifting then continues to the 500-hPa level via the combined effects of topography and frequent, deep, and dry convective updrafts over the mountainous areas of the northern ICP. The smoke aerosols are subsequently transported to South China and the western Pacific owing to strong westerly winds and weak vertical motion. Further analyses demonstrated that differences in meteorological conditions between daytime and nighttime have substantial impact on the vertical structure of smoke aerosols, particularly over the northeast of ICP. Compared to daytime, enhanced updrafts and moisture transport at night favor further lifting of smoke aerosols and greater extinction intensity owing to increased hygroscopic growth. • Springtime smoke aerosols from the ICP can be transported to SC and the WP in the mid–upper troposphere. • Differences in daytime and nighttime of smoke aerosols over the ICP may be caused by circulation and water vapor. • Maximum loadings of smoke aerosols over the ICP are observed at altitudes of 2–4 km due to vertical circulation. [ABSTRACT FROM AUTHOR]

The Sichuan and Chongqing regions suffer from severe haze weather in winter due to the unfavourable atmospheric diffusion conditions. Reanalysis and precipitation datasets were applied in this study to calculate and distinguish air stagnation events using a developed criterion, and the impacts of the occurrence of air stagnation events on air quality were analysed in combination with the PM 2.5 concentration data for the winters of 2013–2016. The highest occurrence frequency of air stagnation events was observed in 2013, and the lowest, 2015. The meteorological conditions during winter in the Sichuan Basin were inclined to form unfavourable atmospheric diffusion conditions, and the occurrence frequency of air stagnation days was up to 76.6% on average during the four winters. The effects of air stagnation events on air quality were most obvious in the western and southern Sichuan Basin. The mean concentrations of PM 2.5 during air stagnation days were higher by 41.9% than those during non-air stagnation days. The PM 2.5 concentrations were adjusted using the favourable atmospheric diffusion conditions in 2015 as a baseline to quantify the PM 2.5 contribution to the improvement of air quality in the other years, which revealed that the level of PM 2.5 in the Sichuan and Chongqing regions was declining at a rate of approximately 10.7% overall during the winters of 2013–2016, implying that the air pollutant reduction measures have been highly effective. Furthermore, the occurrence frequency of air stagnation days and events were increased in recent ten years of 2007–2016, with linear slopes of 0.61 yr −1 and 0.26 yr −1 , respectively. The study revealed that the government might face a greater challenge in improving the air quality over winter and should pay more attention to reduction of pollutant emission in areas of Chengdu, Chongqing and cities in the south of the Sichuan Basin. [ABSTRACT FROM AUTHOR]

The vertical structure of aerosols plays an important role in regional air pollution and climate change. Using long-term data on aerosol optical properties obtained through satellite observations (MODIS/Terra, MODIS/Aqua, CALIOP) and reanalysis products (CAMS) during 2007–2021, we analysed the seasonal evolution and vertical distribution of aerosol loading in northeastern China (NEC). We also analysed the seasonal variation trends of aerosol optical depth (AOD) of aerosol species. The AODs during spring and summer were high and distributed in Liaoning (LN) with an average value of approximately 0.6, which was higher in central Jilin and southern Heilongjiang. Sulfate AOD (AOD_SO 4) and organic matter AOD (AOD_OM) in NEC were higher during spring and summer (approximately 0.2), and the maximum value of dust AOD (AOD_DU) was approximately 0.1 obtained for western LN. During spring, the aerosol extinction coefficient (AEC) for NEC was high at heights below 2.0 km in LN, and its value was maximum (approximately 0.16 km−1) near the ground in LN during winter. The AEC was concentrated within 0–1 km during winter and higher within 1–3 km during spring and summer in NEC. During 2007–2021, AOD exhibited a decreasing trend, with higher average AOD during spring and summer and lower average AOD during autumn and winter. The seasonal trend of AOD in NEC exhibited a decreasing trend. BC_AOD showed the largest decline in spring, followed by DU_AOD and OM_AOD, and SO4_AOD showed a significant decline in summer. This paper presents accurate information on regional types and vertical distribution of aerosols. This information can be used for model improvement and satellite validation. [Display omitted] • AOD_SO4 was higher in summer, and AOD_OM was larger during spring in radial. • The annual decreased aerosol extinction was vertically distributed within 0–3 km. • Type-dependent seasonal AOD exhibited an interannual decreasing trend in NEC. [ABSTRACT FROM AUTHOR]

Water vapor is one of the major greenhouse gases in the atmosphere and also the key parameter affecting the hydrological cycle, aerosol properties, aerosol-cloud interactions, the energy budget, and the climate. This study analyzed the temporal and spatial distribution of precipitable water vapor (PWV) in China using MODerate resolution Imaging Spectroradiometer near-infrared (MODIS-NIR)-Clear PWV products from 2011 to 2013. We then compared the four PWV products (Global Positioning System PWV (GPS-PWV), radiosonde PWV (RS-PWV), MODIS-NIR-Clear PWV, and Aerosol Robotic Network sunphotometer PWV (AERONET-PWV)) at six typical sites in China from 2011 to 2013. The analysis of the temporal and spatial distribution showed that the PWV distribution in China has clear geographical differences, and its basic distribution characteristics gradually change from the coast in the southeast to inland in the northwest. Affected by the East Asian monsoon, the PWV over China showed clear seasonal distribution features, with highest values in the summer, followed by autumn and spring, and the lowest values in winter. Intercomparison results showed that GPS-PWV and RS-PWV had a slightly higher correlation (R 2 = 0.975) at 0000 UTC than that at 1200 UTC (R 2 = 0.967). The mean values of Bias, SD, and RMSE between GPS-PWV and RS-PWV (GPS-RS) were − 0.03 mm, 2.36 mm, and 2.60 mm at 0000 UTC, and − 0.23 mm, 2.76 mm, and 2.95 mm at 1200 UTC, respectively. This showed that GPS-PWV was slightly lower than RS-PWV, and this difference was more obvious during the nighttime. The MODIS-NIR-Clear PWV product showed a similar correlation coefficient (R 2 = 0.88) with GPS-PWV compared with RS-PWV. In addition, MODIS-NIR-Clear PWV was greater than GPS-PWV and RS-PWV. The MODIS-NIR-Clear PWV showed a larger deviation from GPS-PWV (MODIS-GPS Bias = 1.50 mm, RMSE = 5.76 mm) compared with RS PWV (MODIS-RS Bias = 0.75 mm, RMSE = 5.31 mm). The correlation coefficients between AERONET-PWV and the PWV from GPS, RS, and MODIS-NIR-Clear were 0.970, 0.963, and 0.923 (with RMSE of 2.53 mm, 3.67 mm, and 4.39 mm), respectively. In the Beijing area, the overall mean bias of the AERONET-PWV product with GPS-PWV, RS-PWV and MODIS-NIR-Clear PWV was − 0.09 mm, − 1.82 mm, and − 1.54 mm, respectively, which shows that the AERONET-PWV product was lower than the other three PWV products. [ABSTRACT FROM AUTHOR]

This study analyzes the annual and seasonal trends in precipitable water vapor (PWV) and surface temperature ( T s ) over China from 1979 to 2015, and the relationships between PWV and T s and between PWV and aerosol absorption optical depth (AAOD), using data from radiosonde stations, weather stations and multiple satellite observations. The results revealed a positive PWV trend between 1979 and 1999, and a negative PWV trend between 2000 and 2015. Analysis of the differences in the PWV trend among different stations types showed that the magnitude of the trends were in the order main urban stations > provincial capital stations > suburb stations, suggesting that anthropogenic activities have a strong influence on the PWV trend. The AAOD exhibited a significant positive trend in most regions of China from 2005 to 2015 (confidence level 95%). Using spatial correlation analysis, we showed that PWV trend derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations is correlated with T s , with an annual correlation coefficient of 0.596. In addition, the spatial correlation between PWV and AAOD showed a negative relationship, with the highest correlation coefficients of −0.76 and −0.71 observed in mid-eastern China and central northwest China, respectively, suggesting that the increase in AAOD in recent years may be one of the reasons for the decrease in PWV since the 2000s in China. [ABSTRACT FROM AUTHOR]

Aerosol loading and properties have an important influence on the radiative effect of aerosols and regional climate change. Based on the long-term datasets of aerosol optical products retrieved from multiple satellite observations (MODIS/Terra, MODIS/Aqua, MISR, and CALIOP/CALIPSO) and a reanalysis product (CAMS) from 2007 to 2019, the climatology and interannual variability in total aerosol optical depth (AOD) and type-dependent AODs related to aerosol particle properties and components over southwest China (SWC) and northern India (NI) are investigated, and the vertical distribution of type-dependent aerosol extinctions are also examined. Overall, consistent spatial distribution characteristics of the AOD climatology are captured across the different datasets, albeit with slight differences in magnitude. Multi-year mean high AODs are mainly concentrated in areas such as the Sichuan Basin (SCB) (∼0.5) and NI (∼0.6), dominated by anthropogenic aerosols, and the Tarim Basin (∼0.5), dominated by mineral dust aerosols. In contrast, the central Tibetan Plateau (CTP) area, with a relatively clean background, has a lower AOD (∼0.1) on a multi-year average basis. When the total AOD is separated by chemical components, the CAMS reanalysis demonstrates that sulfate and carbonaceous aerosols (CAs) contribute nearly equally to AOD in SCB, while CAs is the largest contributor to the high aerosol loading in NI. An enhanced vertical aerosol extinction coefficient (AEC) is mainly located below 1 km in both SCB and NI, reaching 0.35 km−1 and 0.55 km−1. In CTP, the AEC has two peaks (∼0.02 km−1) at 2.5 km and 3.5 km. By partitioning the column AOD by different altitude ranges, we find that about 73.8% (80.6%) of the AOD in SCB (NI) is located in the lower troposphere (0–2 km). The resulting trend analyses show that a significant decreasing (increasing) trend (P < 0.05) in AOD in SCB (NI) is accurately captured by both the satellite products and the CAMS reanalysis. In contrast, a significant decline (P < 0.1) in the CTP region is observed in CAMS only, while a non-significant decline is detected in the satellite products. The results of this study have potential implications for understanding the vertical distribution and interannual variability of regional aerosol loading. • Climatology of type-dependent AODs over SWC and NI were presented. • Sulfate and CAs contribute nearly equally to AOD in SCB. • CAs is the largest contributor to the high aerosol loading in NI. • About 73.8% (80.6%) of the AOD in SCB (NI) is located within 0–2 km. • A significant decreasing (increasing) AOD trend in SCB (NI) is captured. [ABSTRACT FROM AUTHOR]

Notable warming trends have been observed in the Arctic, with tropospheric aerosols being one of the key drivers. Here the seasonal cycles of three-dimensional (3D) distributions of aerosol extinction coefficients (AECs) and frequency of occurrences (FoOs) for different aerosol subtypes in the troposphere over the Arctic from 2007 to 2019 are characterized capitalizing on Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) Level-3 gridded aerosol profile product. Seasonal contributions of total and type-dependent aerosols through their partitioning within the planetary boundary layer (PBL) and free troposphere (FT) are also quantified utilizing the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) PBL height data. The results show substantial seasonal and geographical dependence in the distribution of aerosols over the Arctic. Sulfate, black carbon (BC), and organic carbon (OC) contribute most of the total AEC, with Eurasia being the largest contributor. The vertical structure of AECs and FoOs over the Arctic demonstrates that the vertical influence of aerosols is higher in eastern Siberia and North America than in northern Eurasia and its coasts. When the total aerosol optical depth (TAOD) is partitioned into the PBL and FT, results indicate that the contributions of TAOD within the FT tend to be more significant, especially in summer, with the FT contributes 64.2% and 69.2% of TAOD over the lower (i.e., 60° N–70° N) and high (i.e., north of 70° N) Arctic, respectively. Additionally, seasonal trend analyses suggest Arctic TAOD exhibits a multi-year negative trend in winter, spring, and autumn and a positive trend in summer during 2007–2019, due to an overall decrease in sulfate from weakened anthropogenic emissions and a significant increase in BC and OC from enhanced biomass burning activities. Overall, this study has potential implications for understanding the seasonal cycles and trends in Arctic aerosols. • Seasonal and regional differences in vertical structures of AECs and FoOs are characterized. • The partitioning of TAOD within the PBL and FT are determined. • The decadal trend of the FoOs and AODs for different aerosol subtypes are revealed. [ABSTRACT FROM AUTHOR]

Abstract: We report the electronic properties of a new class of non-fullerene electron acceptor molecules with electron affinities tunable over an approximately 1eV range. This tunability allows us to vary the thermodynamic driving force for electron transfer (ΔG°) such that it is equal-and-opposite-to the reorganization energy for the ionized states (λ). We utilize this design principle, derived from Marcus–Hush theory, to optimize the rate of charge transfer in blends of these acceptors with poly(3-n-hexylthiophene-2,5-diyl) (P3HT) – a standard organic solar cell donor material. We show that computationally inexpensive calculations can be used to parameterize Marcus–Hush theory so as to correctly predict whether quenching will occur. Arguments based solely on energetics are common in the literature and we show that such theories do not predict the trends observed in our photoluminescence quenching experiments. This is the case whether the energies determined from experiments [cyclic voltammetry (CV) and the optical gap] or calculated from density functional theory for the solid state. We predict essentially barrier-less photoelectron transfer (PET) from P3HT to the acceptor 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c] [1,2,5] thiadiazol-4-yl}methylene]malononitrile (or K12), consistent with the experimental photoluminescence quenching efficiencies found for P3HT:K12 blends. Our results clearly show that energetics alone is not sufficient to predict PET between the acceptor–donor pair, and that kinetics are an important determining factor. [Copyright &y& Elsevier]

Abstract: A magnetically stabilized fluidized bed (MSB) is a highly efficient filter that takes the advantage of both fluidized beds and fixed beds. This paper presents the research to collect aerosol in airflow with a MSB. The filtering model of MSB is established with its parameters including magnetic field intensity, gas superficial velocity, average gain-size, and bed height on the collection efficiency of MSB. The model is verified by experiments. [ABSTRACT FROM AUTHOR]

The spatial-temporal variations of the ground-based and satellite-derived PM 2.5 are crucial for studying air quality, human health, and climate change. However, the existing ground-based PM 2.5 monitoring network has sparsely-distributed sites and satellite cannot give 24-h PM 2.5 , which make it difficult to grasp the spatial and sub-daily variation characteristics of PM 2.5. This study aims to fill that gap by establishing a virtual network of hourly PM 2.5 concentration using the LightGBM model, based on the high-density ground meteorological observations at ~2400 sites across China. The virtual network shows a desirable performance of hourly PM 2.5 estimation across China, with R 2 of 0.86, root-mean-square error values of 14.99 μg/m3, and mean absolute error of 9.48 μg/m3 (the results of Cross-Validation). It also exhibits high spatial-temporal consistencies with the observed PM 2.5. Spatially, the heaviest PM 2.5 pollution is mainly distributed in eastern China (especially the Beijing-Tianjin-Hebei, the Yangtze and Pearl river deltas, and the Sichuan-Chongqing areas). Temporarily, PM 2.5 exhibits remarkable seasonal and diurnal changes characterized by higher concentration in winter and nighttime and lower in summer and daytime. Meanwhile, we found that visibility can be used as the primary predictor in the machine learning model to enhance the accuracy of estimated PM 2.5. The established virtual hourly PM 2.5 network (~2400 stations) provides a more intuitive and detailed PM 2.5 data for us to understand the diurnal variation of PM 2.5 and monitor inter-regional transport of haze over China. It thus is of benefit to the study of air pollution control and related diseases. • Hourly PM 2.5 in China is estimated using high-density weather records by LightGBM. • The model shows a superior estimation accuracy at national, regional, and site scales. • A virtual network of high-accuracy and -density hourly PM 2.5 in China is established. • This network fills the gaps of sparse air quality sites and satellite-derived PM 2.5. [ABSTRACT FROM AUTHOR]

An assessment and verification of the Langley calibration method of the Sun photometer at Mt Foyeding (MFYD) Observatory in Beijing was performed. We explored whether the Langley plot calibration is practicable for this mountainous site by analyzing the aerosol climatology and carrying out a case study. Then, the aerosol optical depth (AOD) results were verified under the reference of AERONET AOD. The results showed that satisfactory atmospheric conditions are present on winter mornings, characterized by a smaller average AOD (~0.09–0.14) and a lower range ratio (~36.97–63.38%) than in the afternoons and over a whole day. The six days selected as the case study all showed stable atmospheric conditions characterized by daily average triplets of <2% for all wavelengths. The residual sum of squares for V 0 λ at all wavelengths was <0.0002 and the residual standard deviation was <0.2%. A large improvement was found in the linear regression at morning relative to the statistics obtained over the whole day, when the coefficient of determination and residual standard deviation were promoted by 0.22–2.90% and ~2.76–23.32, respectively. The final V 0 λ value was derived from 31 days of observation and the deviations from the reference V 0 λ were about −1.69, −1.29, −0.81, −0.42, −0.34, −0.22, −0.63 and −0.36% at 340, 380, 440, 500, 675, 870, 1020 and 1640 nm, respectively. The regression analysis of the AOD validation showed a perfect AOD performance, with 100% of the retrievals lying within the expected error (0.05 ± 10%) from 380 to 1640 nm and 99.99% for the 340 nm band. Good AOD agreement (correlation coefficients > 0.998) and residual standard deviation values ranging from ~0.006 to 0.011 were observed, with the relative mean bias varying from 0.999 to 1.066. The mean biases were concentrated within ±0.02 for the ultraviolet bands and within ±0.01 for the other bands; therefore, the results of this preliminary assessment and verification indicated that the Langley plots method is suitable for photometer calibration at the MFYD Observatory. [ABSTRACT FROM AUTHOR]

Aerosol generated from the economic development and extensive urbanization in northeast China (NEC) could influence aerosol optical properties and affect the regional air quality. The level 3 aerosol optical depth (AOD) of different particle size and shape (spherical or nonspherical) obtained by Multiangle Imaging Spectroradiometer (MISR) version 23 were used to estimate their seasonal, annual, and decadal distribution and contribution in NEC from 2001 to 2018. The highest AOD of approximately 0.3 was found in the central Liaoning urban agglomeration, and the lowest AOD occurred in the mountainous area of NEC; the proportion of spherical AOD in NEC region was more than 90%. The contribution of large AOD was higher in spring, ranging from 28.8% to 29.8%. In spring and summer, small and medium AODs were concentrated in central Liaoning (approximately 0.2–0.3 and 0.06–0.08, respectively). The annual variation in the AOD of different particle size was significantly higher in Liaoning than in Jilin and Heilongjiang. The annual proportions of small and spherical AODs were approximately 60% and 90%, respectively. The annual occurrence of clean conditions with AOD < 0.05 was most common in northern Heilongjiang (approximately 20%). In NEC, the annual occurrence frequencies of 0.05 < AOD < 0.15 and AOD > 0.6 were the highest (approximately 50%) and the lowest (less than 1%), respectively. Interdecadal AOD revealed a positive trend from 2001 to 2008 and a negative trend from 2009 to 2018. The frequency of occurrence trend at different AOD levels also changed from positive to negative between these two periods. The findings in this study are based on the first aerosol retrieval of the newly released MISR in NEC. The results provide a comprehensive understanding of the regional and climatological aerosol extinction with different AOD of size and shape as well as various level bins in NEC. Unlabelled Image • Larger contribution of small size and spherical AOD was found in NEC. • Occurrence frequency was highest for 0.05 < AOD < 0.15 (about 50%) in NEC. • Interdecadal AOD and frequency changed from positive to negative in 2008. [ABSTRACT FROM AUTHOR]

Carbonaceous aerosols and gaseous pollutants emitted from wildfires play a crucial role in both the global climate system and regional air quality. Here, using multisource satellite and ground-based observations combined with reanalysis data, we investigate the three-dimensional evolution of biomass-burning emissions from a forest wildfire event in Liangshan, Southwest China, which occurred from 29 March to 1 April 2020. The meteorological field analysis showed that the negative anomaly of relative humidity and precipitation, as well as the positive anomaly of near-surface wind speed, created favourable conditions for the occurrence and spread of this wildfire event. During the fire, satellite observations suggested a maximum fire radiation power of over 100 MW. In addition, there were significant short-term effects of fire activity on regional air quality, with downwind surface PM 2.5 concentrations at the Xichang site reaching a maximum of approximately 470 μg·m −3 on March 31. Driven by a southwesterly airflow, large amounts of smoke aerosols were transported rapidly to downstream areas, significantly deteriorating air quality, with the maximum value of the aerosol optical depth (AOD) exceeding 2. Moreover, the quantitative evaluation based on Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) reanalysis showed that the instantaneous maximum values of the column mass concentration of black carbon (BC) and organic carbon (OC) reached 9.8 g·m−2 and 1.8 g·m−2 during the fire respectively. Further analysis suggested that the interaction between the lower and upper atmosphere constrained the smoke aerosols to altitudes below approximately 5 km, which was also supported by the vertical distribution of elevated smoke aerosols observed by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Unlabelled Image • Formation characteristic of biomass burning at high altitudes in Sichuan were analysed. • Carbonaceous aerosols and gaseous pollutants increased rapidly during the event. • The plume of the smoke reached up to approximately 5 km. • Interaction between the lower and upper atmosphere affects the transport of the pollutants. [ABSTRACT FROM AUTHOR]

Different types of aerosols play a crucial role in the climate system according to their vertical distributions and optical-radiative properties. Southwest China (SWC), consisting of the Sichuan Basin (SCB), the Yunnan-Guizhou Plateau (YGP) and the Tibetan Plateau (TP), is one of the most topographically complex regions in the world and is also facing varying degrees of air pollution problems caused by local, high-intensity anthropogenic emissions and trans-regional transport of aerosols from surrounding areas. However, a comprehensive understanding of the regional three-dimensional (3D) characteristics of aerosol distribution and evolution over SWC has not to be achieved yet. Here, the seasonal distributions and vertical structures of four types of aerosols, including dust, polluted continental/smoke, polluted dust and elevated smoke, were detected by using the quality controlled CALIPSO Level 2 nighttime aerosol profile product from 2007 to 2016 in this study. The loading of aerosols over the SCB was higher than that over the other regions, and of the sources, polluted continental/smoke and polluted dust, related to anthropogenic sources, contributed the most to the aerosols. However, we also found that polluted continental/smoke and polluted dust have declined since 2013, which was due to the strict regulatory measures implemented for industry emissions and biomass burning in agriculture in recent years. The elevated smoke aerosols over the YGP at an altitude of 3 km in spring were significantly higher than those in other seasons, while the polluted continental/smoke aerosols at an altitude of 1–2 km were higher in autumn and winter than in the other seasons and was considered to be from local biomass burning. The aerosol optical depth (AOD) over the TP was nearly one magnitude lower than that over the other two regions. However, either the dust or polluted continental/smoke from the Qaidam Basin or elevated smoke elevated from the Indo-Gangetic Basin could have been transported to the layer as high as 6 km over the TP. Additionally, the heights of the highest frequencies of AOD for all types of aerosols for the SCB, YGP and TP were 0–2 km, 2–4 km and 4–6 km, respectively. In summer, elevated smoke can rise to heights of 8–10 km on the TP. The results of this study provide an observational basis for further understanding the trans-regional transport of aerosols and their climate effects in SWC. • 3D vertical structure of aerosols over SWC were presented during 2006–2016. • Polluted aerosols over SWC have declined since 2013. • Smoke aerosols are mainly from local emissions and trans-regional transport. • Elevated smoke can rise to heights of 8–10 km over the TP in summer. [ABSTRACT FROM AUTHOR]

Fine particulate matter (PM 2.5) has altered the radiation balance on Earth and raised environmental and health risks for decades but has only been monitored widely since 2013 in China. Historical long-term PM 2.5 records with high temporal resolution are essential but lacking for both research and environmental management. Here, we reconstruct a site-based PM 2.5 dataset at 6 h intervals from 1960 to 2020 that combines long-term visibility, conventional meteorological observations, emissions, and elevation. The PM 2.5 concentration at each site is estimated based on an advanced machine learning model, LightGBM, that takes advantage of spatial features from 20 surrounding meteorological stations. Our model's performance is comparable to or even better than those of previous studies in by-year cross validation (CV) (R2=0.7) and spatial CV (R2=0.76) and is more advantageous in long-term records and high temporal resolution. This model also reconstructs a 0.25 ∘ × 0.25 ∘ , 6-hourly, gridded PM 2.5 dataset by incorporating spatial features. The results show PM 2.5 pollution worsens gradually or maintains before 2010 from an interdecadal scale but mitigates in the following decade. Although the turning points vary in different regions, PM 2.5 mass concentrations in key regions decreased significantly after 2013 due to clean air actions. In particular, the annual average value of PM 2.5 in 2020 is nearly the lowest since 1960. These two PM 2.5 datasets (publicly available at 10.5281/zenodo.6372847, Zhong et al., 2022) provide spatiotemporal variations at high resolution, which lay the foundation for research studies associated with air pollution, climate change, and atmospheric chemical reanalysis. [ABSTRACT FROM AUTHOR]

FeSx (1 ≤ x ≤ 1.14) is one of the most promising conversion-type cathodes as lithium metal batteries due to its low-cost and high energy density. Nevertheless, it suffers from heavy volume change, which brings in fast capacity decay. In this study, we employ four different binders (PVDF, PAN, SBR/CMC, and PAA/CMC) to improve their electrochemical performance. It is found that PAN demonstrates the best performance from 559.5 mAh/g (first) to 458.5 mAh/g (100th) at 0.2 C in the voltage window of 1.0 − 3.0 V. This can be ascribed to its high adhesion strength, good electrical conductivity, low swelling properties, high polarity, and good mechanical stability. The findings highlight the importance of a binder material to guide good cycling stabilities for conversion-type or high-volume change cathodes. [ABSTRACT FROM AUTHOR]

• A virtual ground-based PM 2.5 observation network was constructed. • Daily estimations of PM 2.5 concentrations at ~1000 sites in China were generated. • The model demonstrated good performance in hindcasting historical PM 2.5 levels. • This virtual PM 2.5 network can be used for reconstructing historical PM 2.5 data. With increasing public concerns on air pollution in China, there is a demand for long-term continuous PM 2.5 datasets. However, it was not until the end of 2012 that China established a national PM 2.5 observation network. Before that, satellite-retrieved aerosol optical depth (AOD) was frequently used as a primary predictor to estimate surface PM 2.5. Nevertheless, satellite-retrieved AOD often encounter incomplete daily coverage due to its sampling frequency and interferences from cloud, which greatly affect the representation of these AOD-based PM 2.5. Here, we constructed a virtual ground-based PM 2.5 observation network at 1180 meteorological sites across China using the Extreme Gradient Boosting (XGBoost) model with high-density meteorological observations as major predictors. Cross-validation of the XGBoost model showed strong robustness and high accuracy in its estimation of the daily (monthly) PM 2.5 across China in 2018, with R2 , root-mean-square error (RMSE) and mean absolute error values of 0.79 (0.92), 15.75 μg/m3 (6.75 μg/m3) and 9.89 μg/m3 (4.53 μg/m3), respectively. Meanwhile, we find that surface visibility plays the dominant role in terms of the relative importance of variables in the XGBoost model, accounting for 39.3% of the overall importance. We then use meteorological and PM 2.5 data in the year 2017 to assess the predictive capability of the model. Results showed that the XGBoost model is capable to accurately hindcast historical PM 2.5 at monthly (R 2 = 0.80, RMSE = 14.75 μg/m3), seasonal (R 2 = 0.86, RMSE = 12.28 μg/m3), and annual (R 2 = 0.81, RMSE = 10.10 μg/m3) mean levels. In general, the newly constructed virtual PM 2.5 observation network based on high-density surface meteorological observations using the Extreme Gradient Boosting model shows great potential in reconstructing historical PM 2.5 at ~1000 meteorological sites across China. It will be of benefit to filling gaps in AOD-based PM 2.5 data, as well as to other environmental studies including epidemiology. [ABSTRACT FROM AUTHOR]

Retrieving historical fine particulate matter (PM2.5) data is key for evaluating the long-term impacts of PM2.5 on the environment, human health and climate change. Satellite-based aerosol optical depth has been used to estimate PM2.5, but estimations have largely been undermined by massive missing values, low sampling frequency and weak predictive capability. Here, using a novel feature engineering approach to incorporate spatial effects from meteorological data, we developed a robust LightGBM model that predicts PM2.5 at an unprecedented predictive capacity on hourly (R2 = 0.75), daily (R2 = 0.84), monthly (R2 = 0.88) and annual (R2 = 0.87) timescales. By taking advantage of spatial features, our model can also construct hourly gridded networks of PM2.5. This capability would be further enhanced if meteorological observations from regional stations were incorporated. Our results show that this model has great potential in reconstructing historical PM2.5 datasets and real-time gridded networks at high spatial-temporal resolutions. The resulting datasets can be assimilated into models to produce long-term re-analysis that incorporates interactions between aerosols and physical processes. [ABSTRACT FROM AUTHOR]

Conventional, manual methods of surveying unstable bedrock promontories on high and steep slopes are very risky and time-consuming due to problems regarding steep terrain and traffic inconvenience. This paper describes an unmanned aerial vehicle (UAV)-based method for the identification of unstable bedrock promontories. The first step is the spatial position identification of bedrock promontories, which is implemented by processing point cloud models with the one-class support vector machine (OC-SVM) and clustering algorithm. The next step is the preliminary stability assessment of bedrock promontories. Kinematic analysis by mapping the orientations of penetrative discontinuities within bedrock promontories is used to evaluate the stability. The applicability of the method is assessed using the point cloud model of the bank slopes of the Lianghekou Hydropower Project. The results show that effective identification, and preliminary stability assessment of bedrock promontories can be carried out using UAV photogrammetry. [ABSTRACT FROM AUTHOR]

This study analyzed the long-term variations and trends of haze pollution and its relationships with emission and meteorological factors using the haze days (HDs) data derived from surface observation stations in Sichuan-Chongqing (SCC) region during 1980–2016. The results showed that the multi-year mean number of HDs were 68.7 and 4.9 days for the Sichuan-Basin (SCB) and the rest of SCC region, respectively. The seasonally averaged HDs over SCB reached its maximum in winter (34.7 days), followed by autumn (17.0 days) and spring (11.6 days), and with the minimum observed in summer (5.5 days). The inter-annual variations of HDs in 18 main cities revealed that Zigong, Neijiang, and Yibin, which are located in the southern of SCB, have been the most polluted areas over the SCC region in the past decades. A notable increasing trend in annual HDs over the majority of SCC region was found during 1980–1995, then the trend sharply reversed during 1996–2005, while it increased, fluctuating at some cities after 2006. Seasonally, the increased trend in spring and autumn seems to be the strongest during 1980–1995, whereas the decreased trend in spring and winter was stronger than other seasons during 1996–2005. In addition, a remarkable increasing trend was found in winter since 2006. Using correlation analysis between HDs and emission and meteorological factors during different periods, we found that the variability of local precipitation days (PDs), planetary boundary layer height (PBLH), near-surface wind speed (WS), and relatively humidity (RH) play different roles in influencing the haze pollution change during different historical periods. The joint effect of sharp increase of anthropogenic emissions, reduced PDs and WS intensified the haze pollution in SCB during 1980–1995. In contrast, decreased HDs during 1996–2005 are mainly attributable to the reduction of PM2.5 emission and the increase of PDs (especially in winter). In addition, the decrease of PDs is likely to be responsible for the unexpected increase in winter HDs over SCB in the last decade. [ABSTRACT FROM AUTHOR]

Accurate estimation of the spatiotemporal variations of solar radiation is crucial for assessing and utilizing solar energy, one of the fastest‐growing and most important clean and renewable resources. Based on observations from 2,379 meteorological stations along with scare solar radiation observations, the random forest (RF) model is employed to construct a high‐density network of daily global solar radiation (DGSR) and its spatiotemporal variations in China. The RF‐estimated DGSR is in good agreement with site observations across China, with an overall correlation coefficient (R) of 0.95, root‐mean‐square error of 2.34 MJ/m2, and mean bias of −0.04 MJ/m2. The geographical distributions of R values, root‐mean‐square error, and mean bias values indicate that the RF model has high predictive performance in estimating DGSR under different climatic and geographic conditions across China. The RF model further reveals that daily sunshine duration, daily maximum land surface temperature, and day of year play dominant roles in determining DGSR across China. In addition, compared with other models, the RF model exhibits a more accurate estimation performance for DGSR. Using the RF model framework at the national scale allows the establishment of a high‐resolution DGSR network, which can not only be used to effectively evaluate the long‐term change in solar radiation but also serve as a potential resource to rationally and continually utilize solar energy.Key Points: The RF model exhibits high accuracy and considerable potential in projecting DGSRImportance of possible variables for estimating DGSR is identified by the RF modelSpatiotemporal variations of DGSR across China are constructed from high‐density meteorological observations [ABSTRACT FROM AUTHOR]

Once challenged by the SARS-CoV-2 virus, the human host immune system triggers a dynamic process against infection. We constructed a mathematical model to describe host innate and adaptive immune response to viral challenge. Based on the dynamic properties of viral load and immune response, we classified the resulting dynamics into four modes, reflecting increasing severity of COVID-19 disease. We found the numerical product of immune system's ability to clear the virus and to kill the infected cells, namely immune efficacy, to be predictive of disease severity. We also investigated vaccine-induced protection against SARS-CoV-2 infection. Results suggested that immune efficacy based on memory T cells and neutralizing antibody titers could be used to predict population vaccine protection rates. Finally, we analyzed infection dynamics of SARS-CoV-2 variants within the construct of our mathematical model. Overall, our results provide a systematic framework for understanding the dynamics of host response upon challenge by SARS-CoV-2 infection, and this framework can be used to predict vaccine protection and perform clinical diagnosis. Author summary: Once challenged by the SARS-CoV-2 virus, the host immune system initiates a dynamic process against infection. Countless experimental, clinical, and theoretical studies have been carried out to understand the pathogenesis of SARS-CoV-2 infection, improve treatments or optimize vaccine strategies. Most of the time, people have been focusing on one arm of host immune system during SARS-CoV-2 infection and vaccine protection, despite there are three. A systematic understanding towards the innate, cellular, and humoral immunologic responses remains incomplete. Here, we report a mathematical model that captures the virus-immunity dynamics in both primary infection and vaccine-rendered protection. Mathematical analysis reveals the overall host immune system functions as an integrative dynamic metric combating SARS-CoV-2 infection. The metric reveals the cooperative nature of the immune system, especially between cellular and humoral immune responses. Numerical simulation and data analysis show this metric serves as a strong correlate for disease severity and vaccine protection rates against the original and variant SARS-CoV-2 strains. Our results put forth a systematic framework for understanding the virus-immune interaction during SARS-CoV-2 infection, which could be further deployed for treatment formulation and vaccine optimization. [ABSTRACT FROM AUTHOR]

Water vapor (WV) has a vital effect on global climate change. Using satellite data observed by AURA/MLS and ERA-Interim reanalysis datasets, the spatial distributions and temporal variations of WV were analyzed. It was found that high WV content in the UTLS over the southern Tibetan Plateau is more apparent in summer, due to monsoon-induced strong upward motions. The WV content showed the opposite distribution at 100 hPa, though, during spring and winter. And a different distribution at 121 hPa indicated that the difference in WV content between the northern and southern plateau occurs between 121 and 100 hPa in spring and between 147 and 121 hPa in winter. In the UTLS, it diminishes rapidly with increase in altitude in these two seasons, and it shows a “V” structure in winter. There has been a weak increasing trend in WV at 100 hPa, but a downtrend at 147 and 215 hPa, during the past 12 years. At the latter two heights, the WV content in summer has been much higher than in other seasons. Furthermore, WV variation showed a rough wave structure in spring and autumn at 215 hPa. The variation of WV over the Tibetan Plateau is helpful in understanding the stratosphere-troposphere exchange (STE) and climate change. [ABSTRACT FROM AUTHOR]

Seasonal and diurnal characteristics of the vertical profiles of aerosol properties are essential for detecting the regional transport and the climatic radiative effects of aerosol particles. We have studied the seasonal and diurnal characteristics of the vertical distribution of aerosols in urban Beijing from 2017 to 2021 based on long-term Raman–Mie LiDAR observations. The influence of the vertical distribution of aerosols, the meteorological conditions within the boundary layer, the optical–radiometric properties of aerosols, and their interconnections, were investigated during a heavy haze pollution event in Beijing from 8 to 15 February 2020 using both meteorological and sun photometer data. The aerosol extinction coefficient was highest in summer (0.4 km−1), followed by winter (0.35 km−1), and roughly equal in spring and autumn (0.3 km−1). The aerosol extinction coefficient showed clear daily variations and was different in different seasons as a result of the variation in the height of the boundary layer. During the haze pollution event, the particulate matter mainly consisted of scattered spherical fine particles and the accumulation time of pollutants measured via the AOD440nm and PM2.5 mass concentration was different as a result of the hygroscopic growth of the aerosol particles. This growth increased scattering and led to an increase in the aerosol optical depth. The vertical transport of particulate matter also contributed to the increase in the aerosol optical depth. [ABSTRACT FROM AUTHOR]

The aerosol optical property products of Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis dataset have been extensively investigated on a global or regional scale. However, the understanding of MERRA-2 aerosol component products on an extensive temporal and spatial scale is inadequate. Recently, the aerosol component products have been derived from the observations of Polarization and Directionality of the Earth's Reflectances/Polarization and Anisotropy of Reflectance for Atmospheric Science coupled with observations from a Lidar (POLDER/PARASOL). This study presents a quantitative evaluation of the MERRA-2 reanalysis dust and black carbon (BC) column concentration using independent satellite-based aerosol component concentration retrievals. Both GRASP/Component and MERRA-2 reanalysis products can capture well the temporal variation in dust column concentration over the dust emission resource and downwind dust-dominated regions with the correlation coefficient (R) varying from 0.80 to 0.98. MERRA-2 reanalysis dust products present higher column concentration than GRASP/Component dust retrievals with relative differences of about 20~70%, except in the Taklamakan Desert and Bay of Bengal, where the relative differences can be negative. The differences in dust column concentration over the African dust regions are larger than that over the Asian dust regions. Similar temporal variations in BC column concentration are characterized by both GRASP/Component BC retrievals and MERRA-2 BC products with R of about 0.70~0.90, except in the North China Plain region. We should pay more caution with the regional applicability of MERRA-2 component products when large differences and high correlation coefficients are obtained simultaneously. The results are favorable for identifying the behavior of MERRA-2 reanalysis component estimation in a new view and demonstrate a practical application of the satellite-based component retrievals, which could make more contributions to the improvement of model estimation in the near future. [ABSTRACT FROM AUTHOR]

Human-perceived thermal comfort (known as human-perceived temperature) measures the combined effects of multiple meteorological factors (e.g., temperature, humidity, and wind speed) and can be aggravated under the influences of global warming and local human activities. With the most rapid urbanization and the largest population, China is being severely threatened by aggravating human thermal stress. However, the variations of thermal stress in China at a fine scale have not been fully understood. This gap is mainly due to the lack of a high-resolution gridded dataset of human thermal indices. Here, we generated the first high spatial resolution (1 km) dataset of monthly human thermal index collection (HiTIC-Monthly) over China during 2003–2020. In this collection, 12 commonly used thermal indices were generated by the Light Gradient Boosting Machine (LightGBM) learning algorithm from multi-source data, including land surface temperature, topography, land cover, population density, and impervious surface fraction. Their accuracies were comprehensively assessed based on the observations at 2419 weather stations across the mainland of China. The results show that our dataset has desirable accuracies, with the mean R2 , root mean square error, and mean absolute error of 0.996, 0.693 ∘ C, and 0.512 ∘ C, respectively, by averaging the 12 indices. Moreover, the data exhibit high agreements with the observations across spatial and temporal dimensions, demonstrating the broad applicability of our dataset. A comparison with two existing datasets also suggests that our high-resolution dataset can describe a more explicit spatial distribution of the thermal information, showing great potentials in fine-scale (e.g., intra-urban) studies. Further investigation reveals that nearly all thermal indices exhibit increasing trends in most parts of China during 2003–2020. The increase is especially significant in North China, Southwest China, the Tibetan Plateau, and parts of Northwest China, during spring and summer. The HiTIC-Monthly dataset is publicly available from Zenodo at 10.5281/zenodo.6895533 (Zhang et al., 2022a). [ABSTRACT FROM AUTHOR]

The role of PM 2.5 (particles with aerodynamic diameters ≤ 2.5 µm) deposition in air quality changes over China remains unclear. By using the three-year (2013, 2015, and 2017) simulation results of the WRF/CUACE v1.0 model from a previous work (Zhang et al., 2021), a non-linear relationship between the deposition of PM 2.5 and anthropogenic emissions over central-eastern China in cold seasons as well as in different life stages of haze events was unraveled. PM 2.5 deposition is spatially distributed differently from PM 2.5 concentrations and anthropogenic emissions over China. The North China Plain (NCP) is typically characterized by higher anthropogenic emissions compared to southern China, such as the middle-low reaches of Yangtze River (MLYR), which includes parts of the Yangtze River Delta and the Midwest. However, PM 2.5 deposition in the NCP is significantly lower than that in the MLYR region, suggesting that in addition to meteorology and emissions, lower deposition is another important factor in the increase in haze levels. Regional transport of pollution in central-eastern China acts as a moderator of pollution levels in different regions, for example by bringing pollution from the NCP to the MLYR region in cold seasons. It was found that in typical haze events the deposition flux of PM 2.5 during the removal stages is substantially higher than that in accumulation stages, with most of the PM 2.5 being transported southward and deposited to the MLYR and Sichuan Basin region, corresponding to a latitude range of about 24°N-31°N. [Display omitted] [ABSTRACT FROM AUTHOR]

In the springs of 2021 and 2023, northern East Asia experienced intense dust activities resulting in significant environmental and ecological impacts. This study explores the climate factors responsible for these strong dust activities in both springs. Results show that the anomalous surface warming during the late winter and early spring and the anomalous dry surface soil moisture in the spring are the underlying surface factors contributing to the occurrence of intense dust activities in these two years. Furthermore, we find that the anomalous wave patterns over the Eurasian continent are dynamic factors driving the initiation of dust activities in these two springs. The intensified north-south pressure gradient in Gobi Desert (GD) associated with the wave patterns significantly increases near-surface wind speeds, favoring the occurrence of dust activities. The sea surface temperature (SST) anomalies in the North Atlantic and tropical eastern Pacific can significantly influence the wind speed anomalies in northern East Asia, thereby impacting dust activities. In 2021, the increase in wind speed in the GD was influenced by both the warm SST anomalies in the North Atlantic and the cold SST anomalies in the tropical eastern Pacific. Nevertheless, in 2023, the predominant influence came from the exceptionally strong warming in the North Atlantic, offsetting the opposing effect of warm SST anomalies in the tropical eastern Pacific. Sensitivity experiments confirm the important role of the SST anomalies in the North Atlantic and tropical eastern Pacific on the dust activities in GD. These findings play an insight into understanding of the mechanisms behind the recent variations in dust activities in northern East Asia. • Surface warming and drier soils are the surface factors responsible for the intense dust activities in 2021 and 2023. • SST anomalies in the North Atlantic and tropical Pacific can influence the wind speed in Gobi Desert (GD), thereby impacting dust activities. • Sensitivity experiments confirm the important role of the SST anomalies in the key regions on the dust activities in GD. [ABSTRACT FROM AUTHOR]

An evaluation of aerosol microphysical, optical and radiative properties measured with a multiwavelength photometer named CW193 was performed in this study. The instrument has a highly integrated design, smart control performance and is composed of three parts (the optical head, robotic drive platform and stents system). Based on synchronous measurements, the CW193 products were validated using reference data from the AERONET CE318 photometer. The results show that the raw digital counts from CW193 agree well with the counts from AERONET (R>0.989), with daily average triplets of around 1.2 % to 3.0 % for the ultraviolet band and less than 2.0 % for the visible and infrared bands. Good aerosol optical depth agreement (R>0.997 , 100 % within expected error) and root mean square error (RMSE) values ranging from 0.006 (for the 870 nm band) to 0.016 (for the 440 nm band) were obtained, with the relative mean bias (RMB) ranging from 0.922 to 1.112 and the aerosol optical depth bias within ±0.04. The maximum deviation of the peak value for fine-mode particles varied from about 8.9 % to 77.6 %, whereas the variation for coarse-mode particles was about 13.1 % to 29.1 %. The deviation variations of the single scattering albedo were approximately 0.1 %–1.8 %, 0.6 %–1.9 %, 0.1 %–2.6 % and 0.8 %–3.5 % for the 440, 675, 870 and 1020 nm bands, respectively. For the aerosol direct radiative forcing, deviations of approximately 4.8 %–12.3 % were obtained at the earth's surface and 5.4 %–15.9 % for the top of the atmosphere. In addition, the water vapor retrievals showed satisfactory accuracy, characterized by a high R value (∼0.997), a small RMSE (∼0.020) and a good expected error distribution (100 % within expected error). The water vapor RMB was about 0.979, and the biases mostly varied within ±0.04 , whereas the mean values were concentrated within ±0.02. [ABSTRACT FROM AUTHOR]

The study presents a climatology of aerosol composition concentrations obtained by a recently developed algorithm approach, namely the Generalized Retrieval of Atmosphere and Surface Properties (GRASP)/Component. It is applied to the whole archive of observations from the POLarization and Directionality of the Earth's Reflectances (POLDER-3). The conceptual specifics of the GRASP/Component approach is in the direct retrieval of aerosol speciation (component fraction) without intermediate retrievals of aerosol optical characteristics. Although a global validation of the derived aerosol component product is challenging, the results obtained are in line with general knowledge about aerosol types in different regions. In addition, we compare the GRASP-derived black carbon (BC) and dust components with those of the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) product. Quite a reasonable general agreement was found between the spatial and temporal distribution of the species provided by GRASP and MERRA-2. The differences, however, appeared in regions known for strong biomass burning and dust emissions; the reasons for the discrepancies are discussed. The other derived components, such as concentrations of absorbing (BC, brown carbon (BrC), iron-oxide content in mineral dust) and scattering (ammonium sulfate and nitrate, organic carbon, non-absorbing dust) aerosols, represent scarce but imperative information for validation and potential adjustment of chemical transport models. The aerosol optical properties (e.g., aerosol optical depth (AOD), Ångström exponent (AE), single-scattering albedo (SSA), fine- and coarse-mode aerosol optical depth (AODF AND AODC)) derived from GRASP/Component were found to agree well with the Aerosol Robotic Network (AERONET) ground reference data, and were fully consistent with the previous GRASP Optimized, High Precision (HP) and Models retrieval versions applied to POLDER-3 data. Thus, the presented extensive climatology product provides an opportunity for understanding variabilities and trends in global and regional distributions of aerosol species. The climatology of the aerosol components obtained in addition to the aerosol optical properties provides additional valuable, qualitatively new insight about aerosol distributions and, therefore, demonstrates advantages of multi-angular polarimetric (MAP) satellite observations as the next frontier for aerosol inversion from advanced satellite observations. The extensive satellite-based aerosol component dataset is expected to be useful for improving global aerosol emissions and component-resolved radiative forcing estimations. The GRASP/Component products are publicly available (https://www.grasp-open.com/products/ , last access: 15 March 2022) and the dataset used in the current study is registered under 10.5281/zenodo.6395384 (Li et al., 2022b). [ABSTRACT FROM AUTHOR]

Winter construction in seasonally frozen soil areas is inevitable. The variation of ambient temperature causes the freeze-thaw of the filling soils and its impact is significant, and whether the countermeasures can be effectively established and adopted is particularly important for the management and control of the construction quality of the project. This paper conducts systematic research based on the winter construction process of the dam core wall of the Lianghekou Hydropower Station, which is the third highest earth-core rockfill dam in the world under construction. The results show that for the construction site in the seasonally frozen soil area, there is a development process of the short-term frozen soils for the filling soils under the environment with low temperature in winter. The soil underwent a high-frequency freeze-thaw process wherein it was frozen at night and completely thawed during the day. During the freezing process, a large number of thin-layered segregated ice developed inside the soil to form a thin-layered or integral cryostructure, which will have an adverse effect on the engineering properties and the quality of the filling soils. And, the field tests demonstrate that the filling compaction degree of the frozen soils is difficult to meet the designed requirements. In order to effectively cope with the adverse effect of the freeze-thaw on the construction quality during the construction process, based on the analysis of the freeze-thaw characteristics of soils and its influence, and the energy exchange process of soils on-site, the principles and methods for establishing the freeze prevention system during the winter construction process are established, and a comprehensive monitoring system suitable for on-site is established in this paper. This research will provide an important reference for the scientific management and efficiency improvement of the winter construction process of the dams in cold regions. [ABSTRACT FROM AUTHOR]

The development of chemical transport models with advanced physics and chemical schemes could improve air-quality forecasts. In this study, the China Meteorological Administration Unified Atmospheric Chemistry Environment (CUACE) model, a comprehensive chemistry module incorporating gaseous chemistry and a size-segregated multicomponent aerosol algorithm, was coupled to the Weather Research and Forecasting (WRF) framework with chemistry (WRF-Chem) using an interface procedure to build the WRF/CUACE v1.0 model. The latest version of CUACE includes an updated aerosol dry deposition scheme and the introduction of heterogeneous chemical reactions on aerosol surfaces. We evaluated the WRF/CUACE v1.0 model by simulating PM 2.5 , O3 , NO2 , and SO2 concentrations for January, April, July, and October (representing winter, spring, summer and autumn, respectively) in 2013, 2015, and 2017 and comparing them with ground-based observations. Secondary inorganic aerosol simulations for the North China Plain (NCP), Yangtze River Delta (YRD), and Sichuan Basin (SCB) were also evaluated. The model captured well the variations of PM 2.5 , O3 , and NO2 concentrations in all seasons in eastern China. However, it is difficult to accurately reproduce the variations of air pollutants over SCB, due to its deep basin terrain. The simulations of SO2 were generally reasonable in the NCP and YRD with the bias at -15.5 % and 24.55 %, respectively, while they were poor in the Pearl River Delta (PRD) and SCB. The sulfate and nitrate simulations were substantially improved by introducing heterogeneous chemical reactions into the CUACE model (e.g., change in bias from -95.0 % to 4.1 % for sulfate and from 124.1 % to 96.0 % for nitrate in the NCP). Additionally, The WRF/CUACE v1.0 model was revealed with better performance in simulating chemical species relative to the coupled Fifth-Generation Penn State/NCAR Mesoscale Model (MM5) and CUACE model. The development of the WRF/CUACE v1.0 model represents an important step towards improving air-quality modeling and forecasts in China. [ABSTRACT FROM AUTHOR]

Aerosols are important atmospheric constituents with significant impacts on both regional air quality and the global climate and environment. Aerosol effects on radiation, clouds and precipitation are strongly related to the optical properties of aerosols, which vary considerably in space and time. This study reviewed the current understanding of the optical and radiative properties of aerosols and aerosol effects in China, and presented future research prospects. The Chinese aerosol remote sensing network (CARSNET) has been developed and expanded to include >80 stations across China. An internationally recognized radiometric calibration and data processing method has been developed to provide high-quality observational data of key optical properties. Ground lidars are used to provide information on the vertical aerosol optical properties on the spatiotemporal scales. The spatio-temporal distribution and evolution of aerosols are also analyzed using multi-satellite observations. Particle type and component content information are derived from aerosol component retrieval algorithm. Given the advantages of aerosol assimilation reanalysis products in terms of temporal resolution and spatial coverage, such information can more accurately characterize the climatological impact of aerosol optical properties and aerosol–climate interactions. Measurements obtained using the above methods can quantitatively reveal the influence of aerosol direct radiation effects in different regions, and support the exploration of the potential mechanisms of aerosol impacts on weather and climate from the perspective of ground-based remote sensing, which will help to guide the direction of future research. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals (PeNCs) are emerging as one of the most promising materials for optoelectrical devices such as light‐emitting diode (LED) owing to their tunable band gaps, high color purity, and tolerance to defects. Nevertheless, the materials have not yet demonstrated their full potential in practical applications due to the poor stability of PeNCs and their unsatisfactory performance in devices. In this research, LED devices based on CsPbBr3 NCs are successfully demonstrated as an active light‐emitting layer with enhanced efficiency via potassium doping. The study of the effect of potassium dopant on physicochemical properties of inorganic CsPbBr3 PeNCs shows that potassium cations (K+) remain in the crystal structure of perovskite compound as interstitial defects, which results in better coverage of surface ligands on the PeNCs and improved energy band alignment with adjacent electron injection layer (2,2′,2′‐(1,3,5‐benzinetriyl)‐tris(1‐phenyl‐1‐H‐benzimidazole)) and hole injection layer (poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate) in an LED. As a consequence, the green LED with the K‐doped CsPbBr3 PeNCs shows luminance up to 5759 cd m‐2 and external quantum efficiency (EQE) of 5.6%, which is superior to the pristine device without K‐doping (luminance: 4579 cd m‐2, EQE: 4.8%). [ABSTRACT FROM AUTHOR]

We report on the charge transport properties of a simple solution processable small-molecule electron acceptor, 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile (K12), designed for use in bulk-heterojunction organic photovoltaic cells. It was found that the molecular order in as-cast films can be dramatically improved by annealing at moderate temperatures (60 °C), which leads to a greatly enhanced electron mobility. Using the photoinduced charge extraction in linearly increasing voltage technique we measured bulk electron mobilities to be as high as 10-4 cm2 V-1 s-1, comparable with some of the best nonfullerene acceptor materials reported to date. [ABSTRACT FROM AUTHOR]

Northeast China has undergone rapid urbanisation with increased anthropogenic emissions, and the types and absorption properties of aerosols may affect regional climate change. MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, version 2) distributions of aerosol optical depth (AOD), Ångström exponent (AE), and absorption aerosol optical depth (AAOD) from 1980 to 2017 was studied to estimate the climatology of aerosol optical properties over Northeast China. The highest AOD and AAOD occurred in Liaoning Province range from 0.3 to 0.4 and 0.02–0.03, respectively. The spacial distribution of black carbon (BC) AOD was similar to AAOD with maximum value in Liaoning province about 0.04 related to the emission sources and human activities. The seasonal interdecadal distribution indicated larger dust (DU) AOD in Liaoning (0.12) and organic carbon (OC) AOD in Heilongjiang (0.18). The contribution of SO 4 to total AOD was significant in autumn and winter, and BC particles contributed 70% to total AAOD in all seasons. The decadal change in AOD was positive for 2000–2009 (0.2/decadal) due to the increased dust events happening in spring. The positive correlation between AOD and relative humidity (RH) at surface was about 0.4–0.6; the negative correlation between AOD and surface wind speed (WS) (−0.6), planetary boundary layer height (PBLH) (−0.2 to −0.6), sea level pressure (SLP) (−0.2) was found over the study period. This study's findings enable more comprehensive understanding of the distribution of aerosols optical properties and regional climatology in Northeast China. • Higher interdecadal AOD andAAOD wereobviouslyfound in Liaoning Province. • The contribution of SO4 and BC was significantto total AOD and AAOD. • Meteorological factors havelarge influence on regional aerosol extinction. [ABSTRACT FROM AUTHOR]

This study used the MERRA-2 reanalysis dataset and ground-based and satellite observational data to comprehensively analyze a typical dust storm event in east Asia on 2–7 May 2017 which engulfed most of China as well as ocean and Japan, and explore the accuracy and comprehensiveness of the MERRA-2 dataset in the analysis of dust processes. The results of comparison show that the description of the spatiotemporal distribution and evolution of the dust aerosols in the dust event using the MERRA-2 data is consistent with the data of AERONET, National Urban Air Quality Real-time Publishing Platform and Hamawari-8. Gobi Deserts was the most influential source area of this dust event with the highest emissions reaching 1.9 × 106 μg/m3. The vertical motion of the atmosphere can lift dust from the source area above 500 hPa. There were low-pressure troughs at 500 and 850 hPa and the winds behind and in front of the trough led to the high-altitude, long-distance transport of dust. Dust gradually affected the northwest China, north China, northeast China, and even the ocean and Japan on 2–7 May. This study demonstrates that although there is some uncertainty about the source of dust emission in the MERRA-2 model, the data accurately simulated the evolution of the dust event and analyze it comprehensively, while the accuracy of simulating the long-term evolution of dust requires further evaluation. [ABSTRACT FROM AUTHOR]

The development of chemical transport models with advanced physics and chemical schemes could improve air-quality forecasts. In this study, the China Meteorological Administration Unified Atmospheric Chemistry Environment (CUACE) model, a comprehensive chemistry module incorporating gaseous chemistry and a size-segregated multicomponent aerosol algorithm, was coupled to the Weather Research and Forecasting (WRF)-Chem framework using an interface procedure to build the WRF/CUACE v1.0 model. The latest version of CUACE includes an updated aerosol dry deposition scheme and the introduction of heterogeneous chemical reactions on aerosol surfaces. We evaluated the WRF/CUACE v1.0 model by simulating PM[sub 2.5], O[sub 3], and NO[sub 2] concentrations for January, April, July, and October (representing winter, spring, summer, and autumn, respectively) in 2013, 2015, and 2017 and comparing them with ground-based observations. Secondary inorganic aerosol simulations were also evaluated through a simulation of a heavy haze pollution event during 9-15 January 2019 in the North China Plain. The model well captured the variations of PM[sub 2.5], O[sub 3], and NO[sub 2] concentrations in all seasons in eastern China. However, it is difficult to accurately reproduce the variations of air pollutants over Sichuan Basin, due to its deep basin terrain. The sulfate and nitrate simulations are substantially improved by introducing heterogenous chemical reactions into the CUACE model (change in bias from -95.0% to 4.1% for sulfate and from 124.1% to 96.0% for nitrate). The development of the WRF/CUACE v1.0 model represents an important step towards improving air-quality modelling and forecasts in China. [ABSTRACT FROM AUTHOR]

Herein we demonstrate a new method for the synthesis of methylammonium lead bromide perovskite nanocrystals (MAPbBr3) by using environmentally friendly ionic liquids. The effects of different carboxylate anions in ionic liquids on crystal growth and the properties of MAPbBr3 were investigated. This work paves a new avenue for the sustainable synthesis of perovskite materials by using ionic liquid based green solvents. [ABSTRACT FROM AUTHOR]

Atmospheric aerosol levels are high in different regions of China. Changes in atmospheric stability and mixing layer height (MLH) may affect the vertical aerosol distribution during pollution events. Here, we continuous studied the spatiotemporal distribution of MLH in China over 2000–2013 to characterize the regional-scale properties of atmospheric boundary layers. MLH was larger in the Southern Coastal and Southeastern China (1241.5 ± 73.5 and 632.7 ± 61.8 m, respectively), but lower in Eastern and Southwestern China (518.1 ± 63.6 and 462.7 ± 88.5 m, respectively). We divided the monitoring stations into 11 regions; these regions could be classified into three types with an increasing linear trend (95% confidence level), with a decreasing linear trend (95% confidence level), and with fluctuation changes. In all regions, MLH was higher in spring and summer than in autumn and winter. The spatial distribution of the diurnal MLH increased significantly at 1400 BJT (Beijing time) in all regions, with the strongest radiation being noted during the daytime. Higher levels of PM 2.5 with corresponding lower MLH were noted during winter, indicating that lower MLH could confine the pollutant diffusion to near the surface. By contrast, in spring, higher MLH could be potentially due to the dynamic condition. In general, the poor air quality days occurred more frequently in winter than in other seasons. As the air quality worsened, most MLH showed a decreasing trend in almost all regions. This work provides information that aids in further understanding not only MLH distribution in China but also specific PM–MLH interaction to facilitate regional atmospheric environment monitoring and prediction. • Greater MLH was found in Southern and lower MLH in Southwestern China. • The annual MLH with increasing/declining/fluctuating trends were found. • Interaction between PM and MLH contributed to the regional air quality. [ABSTRACT FROM AUTHOR]

The aerosol microphysical, optical and radiative properties of the whole column and upper planetary boundary layer (PBL) were investigated during 2013 to 2018 based on long-term sun-photometer observations at a surface site (~106 m a.s.l.) and a mountainous site (~1225 m a.s.l.) in Beijing. Raman-Mie lidar data combined with radiosonde data were used to explore the aerosol radiative effects to PBL during dust and haze episodes. The results showed size distribution exhibited mostly bimodal pattern for the whole column and the upper PBL throughout the year, except in July for the upper PBL, when a trimodal distribution occurred due to the coagulation and hygroscopic growth of fine particles. The seasonal mean values of aerosol optical depth at 440 nm for the upper PBL were 0.31 ± 0.34, 0.30 ± 0.37, 0.17 ± 0.30 and 0.14 ± 0.09 in spring, summer, autumn and winter, respectively. The single-scattering albedo at 440 nm of the upper PBL varied oppositely to that of the whole column, with the monthly mean value between 0.91 and 0.96, indicating weakly to slightly strong absorptive ability at visible spectrum. The monthly mean direct aerosol radiative forcing at the Earth's surface and the top of the atmosphere varied from −40 ± 7 to −105 ± 25 and from −18 ± 4 to −49 ± 17 W m−2, respectively, and the maximum atmospheric heating was found in summer (~66 ± 12 W m−2). From a radiative point of view, during dust episode, the presence of mineral dust heated the lower atmosphere, thus promoting vertical turbulence, causing more air pollutants being transported to the upper air by the increasing PBLH. In contrast, during haze episode, a large quantity of absorbing aerosols (such as black carbon) had a cooling effect on the surface and a heating effect on the upper atmosphere, which favored the stabilization of PBL and occurrence of inversion layer, contributing to the depression of the PBLH. Unlabelled Image • Aerosol optical properties for upper planetary boundary layer were showed in Beijing. • Aerosol radiative effects to planetary boundary layer were investigated. • Mineral dust heated middle to low atmosphere, thus promoted turbulence. • Absorptive aerosol facilitated the formation of inversion layer in haze episode. [ABSTRACT FROM AUTHOR]

Abstract Serious pollution events caused by residential heating activities occur frequently in northeastern China, and these increased particulate matter levels and gaseous pollutants could contribute to both local emissions and regional climate change. In this study, meteorological data, air trajectories and aerosol vertical distributions were used to study the pollutant sources and movement paths during the heating season (winter–spring transition) in the Harbin-Changchun megalopolis, northeastern China. Higher concentration of fine-mode particles (PM 2.5 /PM 10 ∼ 0.70–0.80) and the trace gas SO 2 (35–45 μg m−3) could be seem as an indicator of the air quality in the Harbin-Changchun megalopolis during the residential heating seasons, caused by local emissions. The apparent changes of meteorological elements in the high latitude and cold regions over Northeastern China could have important effects on the pollutant formation, secondary transformation, aerosol accumulation and vertical transport over the heating season. The PM 2.5 concentrations were highly associated with the SO 2 and NO 2 from both fossil fuel combustion and biomass burning. The obvious diurnal pollutants variation shown thermodynamic conditions could be considered one of the important environmental elements responsible for residential heating processes. The mixture effect of local emissions and aerosol convective activities were found to contribute to the aerosol extinction and air pollution in the Harbin-Changchun megalopolis. These findings could help to improve our understanding of the association between aerosol pollutants influenced by the anthropogenic activities and the aerosol regional climate effects during the heating season in northeastern China. Highlights • Residential heating contributed majority SO2 in northeastern China. • Residential heating significant influenced on different aerosols diurnal variation. • Emphasize the local emission and convective activity to the residential heating. [ABSTRACT FROM AUTHOR]

Abstract The cloud optical depth (COD) is one of the important parameters used to characterize atmospheric clouds. We analyzed the seasonal variations in the COD over East Asia in 2011 using cloud mode data from the AERONET (Aerosol Robotic Network) ground-based observational network. The applicability of the MODIS (Moderate Resolution Imaging Spectroradiometer) COD product was verified and compared with the AERONET cloud mode dataset. There was a good correlation between the AERONET and the MODIS. The spatial and temporal distribution and trends in the COD over China were then analyzed using MODIS satellite data from 2003 to 2016. The seasonal changes in the AERONET data and the time sequence variation of the satellite data suggest that the seasonal variations in the COD are significant. The result shows that the COD first decreases and then increases with the season in northern China, and reaches the maximum in summer and minimum in winter. However, the spatial distribution change is just the opposite in southern China. The spatial variation trend shows the COD in China decreases first with time and gradually increases after 2014. And the trend of COD in the western and central China is consistent with that in China. While the trend of COD shows a continuously increasing over time in northeast China and the Pearl River Delta. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]