Natural Aerosols Research Articles

Changes in aerosol loading before, during and after the COVID-19 pandemic outbreak in China: Effects of anthropogenic and natural aerosol

Anthropogenic emissions reduced sharply in the short-term during the coronavirus disease pandemic (COVID-19). As COVID-19 is still ongoing, changes in atmospheric aerosol loading over China and the factors of their variations remain unclear. In this study, we used multi-source satellite observations and reanalysis datasets to synergistically analyze the spring (February–May) evolution of aerosol optical depth (AOD) for multiple aerosol types over Eastern China (EC) before, during and after the COVID-19 lockdown period. Regional meteorological effects and the radiative response were also quantitatively assessed. Compared to the same period before COVID-19 (i.e., in 2019), a total decrease of −14.6 % in tropospheric TROPOMI nitrogen dioxide (NO2) and a decrease of −6.8 % in MODIS AOD were observed over EC during the lockdown period (i.e., in 2020). After the lockdown period (i.e., in 2021), anthropogenic emissions returned to previous levels and there was a slight increase (+2.3 %) in AOD over EC. Moreover, changes in aerosol loading have spatial differences. AOD decreased significantly in the North China Plain (−14.0 %, NCP) and Yangtze River Delta (−9.4 %) regions, where anthropogenic aerosol dominated the aerosol loading. Impacted by strong wildfires in Southeast Asia during the lockdown period, carbonaceous AOD increased by +9.1 % in South China, which partially offset the emission reductions. Extreme dust storms swept through the northern region in the period after COVID-19, with an increase of +23.5 % in NCP and + 42.9 % in Northeast China (NEC) for dust AOD. However, unfavorable meteorological conditions overwhelmed the benefits of emission reductions, resulting in a +20.1 % increase in AOD in NEC during the lockdown period. Furthermore, the downward shortwave radiative flux showed a positive anomaly due to the reduced aerosol loading in the atmosphere during the lockdown period. This study highlights that we can benefit from short-term controls for the improvement of air pollution, but we also need to seriously considered the cross-regional transport of natural aerosol and meteorological drivers.

Aerosol Property Analysis Based on Ground-Based Lidar in Sansha, China

Marine aerosol is one of the most important natural aerosols. It has a significant impact on marine climate change, biochemical cycling and marine ecosystems. Previous studies on marine aerosols, especially in the South China Sea, were carried out by satellite and shipborne measurements. The above methods have drawbacks, such as low temporal–spatial resolution and signal interference. However, lidar has high accuracy and high temporal–spatial resolution, so it is suitable for high-precision long-term observations. In this work, we obtain marine aerosol data using Mie Lidar in Sansha, an island in the South Chain Sea. Firstly, by comparing boundary layer height (BLH) between Sansha and Hefei, we found that Sansha’s boundary layer height has significant differences with that of inland China. Secondly, we compare the aerosol extinction coefficients and their variation with height in Sansha and Hefei. Finally, we obtain hourly averaged aerosol optical depth at Sansha and explore its relation with weather. To analyze the AOD–weather relation, we select three meteorological factors (sea surface temperature, mean sea level pressure and 10 m u-component of wind) based on their feature importance, which is determined by random forest regression. We also analyze the relationship between AOD and the above meteorological factors in each season separately. The results show that there is a strong relation between the meteorological factors and AOD in spring and summer, while there is no clear correlation in fall and winter. These analyses can provide valid data for future researches on marine aerosols in the South China Sea.

Long-range transport of Asian dust to the Arctic: identification of transport pathways, evolution of aerosol optical properties, and impact assessment on surface albedo changes

Abstract. Airborne dust is one of the most important natural aerosols; it has various environmental impacts on air quality, ocean fertilization, and the global climate change. Asian dust, representing one of the major dust sources in the world, has been widely studied due to its long-range transport capability. However, its transport to the Arctic has been less investigated. In this study, two typical transport routes were identified based on the recorded dust events in China during 2011–2015. Accordingly, two specific Asian dust long-range transport events were selected and compared, i.e., one observed at Barrow, Alaska (traveled mostly over lands within 6–7 d), and the other one observed at Alert, Canada (traveled mostly over oceans within 7–8 d). The transport routes of the two dust events had been cross-validated by using air mass trajectory modeling, meteorology reanalysis data, ground-based aerosol columnar and profiling observations, and spaceborne remote sensing. It was found that different transport routes to the Arctic had divergent effects on the evolution of aerosol properties, revealing different mixing extents between dust, anthropogenic particles, smoke, and sea salts. Based on the Snow, Ice, and Aerosol Radiative (SNICAR) model, the albedo simulation indicated that dust and elemental carbon together reduced the surface albedo by 0.35 % to 2.63 % compared to the pure snow condition. This study implied that the dust long-range transport from China to the Arctic was ubiquitous and may be a potential contributor to the Arctic regional climate.

Response of Indian summer monsoon rainfall to remote carbonaceous aerosols at short time scales: Teleconnections and feedbacks

The effect of atmospheric aerosols on Indian monsoon is one of the scientifically challenging and societally relevant research issues of the recent decades. Past studies have derived inferences mostly based on local emissions and their impacts thereupon. However, more recent studies have shown that the remote effects driven by aerosols elsewhere could also impact the monsoon system on different time scales. Our study using an atmospheric general circulation model (AGCM) shows that regional carbonaceous aerosol emissions (from North America, Europe and North Africa and Asia) can significantly alter Indian summer monsoon rainfall. It is interesting to note that the effects of remote aerosols are larger and bear a resemblance to each other in comparison to local emissions. Our study reveals that the modulation of large-scale circulation induced by regional warming by carbonaceous aerosols leads to teleconnection patterns around the globe, thereby changing the precipitation depending on the phase of these disturbances. We also find that the effects of remote carbonaceous aerosols are strengthened by modulation/feedback through natural dust aerosols over the Arabian Sea with subsequent increase in rainfall over India. The results signify that the changes in the aerosol emissions in one region could lead to the change in precipitation over other regions through global teleconnection and associated feedbacks induced by regional atmospheric warming and/or cooling.

Columnar aerosol optical depth, water vapor and ozone over a semi-arid urban location of western India: Potential sources and direct radiative effects

Continuous measurements of Aerosol Optical Depth (AOD), columnar water vapor (WV) and Ozone (O3) concentrations were made over a semi-arid urban location Rajkot (22.29°N, 70.74°E, and 142 m AMSL) in the western India. The annual mean values of AOD, WV and O3 were 0.37 ± 0.15, 1.44 ± 0.6 gm cm−2 and 243 ± 18 DU during 2016–2019. AOD showed large seasonal variability mostly dominated by abundant coarse mode aerosols (Angstrom Exponent, AE < 0.65 and AOD ∼ 0.37) during pre-monsoon and monsoon, mainly caused by wind-blown and transported dust from nearby Thar and Kutch desert. Mixture of fine and coarse mode aerosols were abundant (AE = 1.13 ± 0.26) during post-monsoon influenced by both anthropogenic and natural sources. Columnar WV were also higher in pre-monsoon and monsoon seasons. The O3 concentrations is higher during pre-monsoon (247 DU) and lower during monsoon (230 DU). The vertical distribution of aerosol extinction coefficient derived from satellite (CALIPSO) based observations revealed the dominance of dust aerosols (∼74 %) in pre-monsoon; smoke and polluted dust in winter and post monsoon period. The trajectory clusters and concentration weighted trajectory maps also indicated the combined effect of anthropogenic (especially from the northern part of India) and natural aerosol sources during the post-monsoon period. Associated with the higher anthropogenic components during post-monsoon season, aerosol direct radiative forcing depicted surface dimming as high as − 48.7 ± 12.6 Wm−2, resulting in atmospheric forcing of 42.6 ± 12.5 Wm−2.

Investigation of Aerosol Types and Vertical Distributions Using Polarization Raman Lidar over Vipava Valley

Aerosol direct radiative forcing is strongly dependent on aerosol distributions and aerosol types. A detailed understanding of such information is still missing at the Alpine region, which currently undergoes amplified climate warming. Our goal was to study the vertical variability of aerosol types within and above the Vipava valley (45.87°N, 13.90°E, 125 m a.s.l.) to reveal the vertical impact of each particular aerosol type on this region, a representative complex terrain in the Alpine region which often suffers from air pollution in the wintertime. This investigation was performed using the entire dataset of a dual-wavelength polarization Raman lidar system, which covers 33 nights from September to December 2017. The lidar provides measurements from midnight to early morning (typically from 00:00 to 06:00 CET) to provide aerosol-type dependent properties, which include particle linear depolarization ratio, lidar ratio at 355 nm and the aerosol backscatter Ångström exponent between 355 nm and 1064 nm. These aerosol properties were compared with similar studies, and the aerosol types were identified by the measured aerosol optical properties. Primary anthropogenic aerosols within the valley are mainly emitted from two sources: individual domestic heating systems, which mostly use biomass fuel, and traffic emissions. Natural aerosols, such as mineral dust and sea salt, are mostly transported over large distances. A mixture of two or more aerosol types was generally found. The aerosol characterization and statistical properties of vertical aerosol distributions were performed up to 3 km.

Bioaerosols in the atmosphere at two sites in Northern Europe in spring 2021: Outline of an experimental campaign

A coordinated observational and modelling campaign targeting biogenic aerosols in the air was performed during spring 2021 at two locations in Northern Europe: Helsinki (Finland) and Siauliai (Lithuania), approximately 500 km from each other in north-south direction. The campaign started on March 1, 2021 in Siauliai (12 March in Helsinki) and continued till mid-May in Siauliai (end of May in Helsinki), thus recording the transition of the atmospheric biogenic aerosols profile from winter to summer.The observations included a variety of samplers working on different principles. The core of the program was based on 2- and 2.4--hourly sampling in Helsinki and Siauliai, respectively, with sticky slides (Hirst 24-h trap in Helsinki, Rapid-E slides in Siauliai). The slides were subsequently processed extracting the DNA from the collected aerosols, which was further sequenced using the 3-rd generation sequencing technology. The core sampling was accompanied with daily and daytime sampling using standard filter collectors. The hourly aerosol concentrations at the Helsinki monitoring site were obtained with a Poleno flow cytometer, which could recognize some of the aerosol types.The sampling campaign was supported by numerical modelling. For every sample, SILAM model was applied to calculate its footprint and to predict anthropogenic and natural aerosol concentrations, at both observation sites.The first results confirmed the feasibility of the DNA collection by the applied techniques: all but one delivered sufficient amount of DNA for the following analysis, in over 40% of the cases sufficient for direct DNA sequencing without the PCR step. A substantial variability of the DNA yield has been noticed, generally not following the diurnal variations of the total-aerosol concentrations, which themselves showed variability not related to daytime. An expected upward trend of the biological material amount towards summer was observed but the day-to-day variability was large.The campaign DNA analysis produced the first high-resolution dataset of bioaerosol composition in the North-European spring. It also highlighted the deficiency of generic DNA databases in applications to atmospheric biota: about 40% of samples were not identified with standard bioinformatic methods.

ИССЛЕДОВАНИЕ РЕЖИМОВ АДСОРБЦИИ МОЛЕКУЛЯРНОГО ЙОДА И ВОЗМОЖНОСТИ МОДИФИКАЦИИ ЛЬДООБРАЗУЮЩИХ ХАРАКТЕРИСТИК АЭРОЗОЛЕЙ СИЛИКАТНОЙ И АЛЮМОСИЛИКАТНОЙ ПРИРОДЫ СОЕДИНЕНИЯМИ ЙОДА

The paper presents the results of studying changes in the ice-forming properties of natural and anthropogenic aerosols containing aluminosilicates when exposed to vaporous iodine. Iodine vapors that are present in the atmosphere as components of natural and anthropogenic pollution and invariably formed during weather modification by pyrotechnic and other means increase the ice-forming activity of natural aerosols, in particular, those having aluminosilicate structures in their composition. It was found that the sorption capacity for molecular iodine vapor for aluminosilicate sorbents is 234 ± 1.0 mg/g. The coefficient of iodine extraction from gas-aerosol media during the sorption in the dynamic mode is 99.5 ± 0.2%. An increase in the ice-forming aerosol activity in this case is from one to three orders of magnitude.

Aerosol Impacts on Water Relations of Camphor (Cinnamomum camphora).

Major parts of anthropogenic and natural aerosols are hygroscopic and deliquesce at high humidity, particularly when depositing to leaf surfaces close to transpiring stomata. Deliquescence and subsequent salt creep may establish thin, extraordinary pathways into the stomata, which foster stomatal uptake of nutrients and water but may also cause stomatal liquid water loss by wicking. Such additional water loss is not accompanied by a wider stomatal aperture with a larger CO2 influx and hypothetically reduces water use efficiency (WUE). Here, the possible direct impacts of aerosols on physical and physiological parameters of camphor (Cinnamomum camphora) were studied (i) in a greenhouse experiment using aerosol exclusion and (ii) in a field study in Taiwan, comparing trees at two sites with different aerosol regimes. Scanning electron microscopy (SEM) images showed that leaves grown under aerosol exclusion in filtered air (FA) were lacking the amorphous, flat areas that were abundant on leaves grown in ambient air (AA), suggesting salt crusts formed from deliquescent aerosols. Increasing vapor pressure deficit (VPD) resulted in half the Ball-Berry slope and double WUE for AA compared to FA leaves. This apparent contradiction to the wicking hypothesis may be due to the independent, overcompensating effect of stomatal closure in response to VPD, which affects AA more than FA stomata. Compared to leaves in a more polluted region in the Taiwanese Southwest, NaCl aerosols dominated the leaf surface conditions on mature camphor trees in Eastern Taiwan, while the considerably lower contact angles and the 2.5 times higher minimum epidermal conductances might have come from organic surfactants. Interpretations of SEM images from leaf surface microstructures should consider amorphous areas as possible indicators of aerosol deposition and other hygroscopic material. The amount and type of the material determine the resulting impacts on plant water relations, together with the surrounding atmosphere and ecophysiological traits.

Anthropogenic pollutants could enhance aridity in the vicinity of the Taklimakan Desert: A case study

With the intensification of human activities, the mixture of anthropogenic pollutants and natural dust aerosols in the vicinity of the Taklimakan Desert (TD) has become a new uncertainty in the weather and climate system. In this study, using a Weather Research and Forecasting model version 4.0 with the Thompson aerosol-aware microphysics scheme, we investigated the impact of anthropogenic aerosols on clouds and precipitation in an atmospheric environment with abundant dust aerosols in the vicinity of the TD. Our findings indicate that anthropogenic aerosols can increase cloud droplet number concentrations in the vicinity of the TD, and the maximum percentage increase can reach 50 %. In addition, the effective radius of water clouds decreases significantly due to anthropogenic aerosols, which means that more numerous but smaller cloud droplets are formed with enhanced anthropogenic aerosol loading under a dusty background. Meanwhile, anthropogenic aerosols can decrease raindrops below 650 hPa, graupel and snow particles, causing less precipitation in the dusty atmosphere surrounding the TD. Furthermore, the anthropogenic aerosol-induced changes in daily precipitation accumulation are also large, with a regionally averaged maximum reduction of up to 4.2 %. Therefore, anthropogenic aerosols are an important factor that exacerbates aridity in the vicinity of the TD, and there is an urgent need to control anthropogenic pollutants around the TD.

Scattering and absorbing aerosols in the climate system

Tropospheric anthropogenic aerosols contribute the second-largest forcing to climate change, but with high uncertainty owing to their spatio-temporal variability and complicated optical properties. In this Review, we synthesize understanding of aerosol observations and their radiative and climate effects. Aerosols offset about one-third of the warming effect by anthropogenic greenhouse gases. Yet, in regions and seasons where the absorbing aerosol fraction is high — such as South America and East and South Asia — substantial atmospheric warming can occur. The internal mixing and the vertical distribution of aerosols, which alters both the direct effect and aerosol–cloud interactions, might further enhance this warming. Despite extensive research in aerosol–cloud interactions, there is still at least a 50% spread in total aerosol forcing estimates. This ongoing uncertainty is linked, in part, to the poor measurement of anthropogenic and natural aerosol absorption, as well as the little-understood effects of aerosols on clouds. Next-generation, space-borne, multi-angle polarization and active remote sensing, combined with in situ observations, offer opportunities to better constrain aerosol scattering, absorption and size distribution, thus, improving models to refine estimates of aerosol forcing and climate effects. Atmospheric aerosols alter Earth’s radiation balance and serve as cloud condensation nuclei, but their climate forcing potential is poorly understood. This Review describes the occurrence of aerosols in the atmosphere, assesses the known impact on climate and proposes approaches to further constrain their climate effects.

Sr-Nd-Hf isotopic analysis of reference materials and natural and anthropogenic particulate matter sources: Implications for accurately tracing North African dust in complex urban atmospheres.

We present novel chemical separation protocols for isotopic analysis of low mass aliquots (0.3mg and 25mg) of several reference materials and real-world samples of relevance to urban airborne particulate matter (PM) investigations. A high-yielding gravity flow column chromatography scheme was developed for facile and quantitative separation of Sr, Nd, and Hf prior to multi collector - inductively coupled plasma - mass spectrometry (MC-ICP-MS). Because we are interested in isolating and accurately quantitating individual anthropogenic and natural aerosol sources in complex industrial/metropolitan atmospheric environments, laboratory protocols were optimized using National Institute of Standards and Technology Standard Reference Material (SRM) 1648a (urban atmospheric PM), SRM 1633b (coal fly ash), and European Commission standards BCR-723 (vehicular road dust), and BCR-2 (basalt rock standard). Sr, Nd, and Hf procedural blanks from column chromatography were low (averaging only 37pg, 17pg, 11pg, respectively) and recoveries were high (averaging 95%, 82%, and 92%, respectively). A volume-adjustment protocol was established using isotope reference solutions SRM 987 (SrCO3), JNdi (Nd2O3), and in-house Hf standards to dilute the dried samples prior to MC-ICP-MS based on projected uncertainties for low sample masses. 87Sr/86Sr, 143Nd/144Nd, and 176Hf/177Hf isotopic ratios in SRM 1648a, BCR-723, and SRM 1633b are reported for the first time that can serve as provisional reference values. The novel method was used to characterize isotopic ratios and elemental abundances in two anthropogenic urban aerosol sources, namely motor vehicles and petroleum refining using airborne fine PM collected in a vehicular tunnel and fluidized-bed catalytic cracking catalysts, respectively. Two other important mineral-rich urban PM sources, namely soil (i.e., resuspended crustal material) and concrete/cement dust (i.e., construction activity) were also characterized. These are the first isotopic measurements in these environmental compartments and were compared with literature data for long-range transported North African dust, which is a prominent summertime PM source in urban regions in southeastern United States. We demonstrate the capability of coupled Sr-Nd-Hf isotopes to uniquely trace different mineral dust sources with overlapping elemental composition (Sahara-Sahel region, local soil, and concrete/cement) and accurately isolate various urban PM sources demonstrating the superiority of isotopic markers over elemental tracers.

Two-way coupled meteorology and air quality models in Asia: a systematic review and meta-analysis of impacts of aerosol feedbacks on meteorology and air quality

Abstract. Atmospheric aerosols can exert an influence on meteorology and air quality through aerosol–radiation interaction (ARI) and aerosol–cloud interaction (ACI), and this two-way feedback has been studied by applying two-way coupled meteorology and air quality models. As one of the regions with the highest aerosol loading in the world, Asia has attracted many researchers to investigate the aerosol effects with several two-way coupled models (WRF-Chem, WRF-CMAQ, GRAPES-CUACE, WRF-NAQPMS, and GATOR-GCMOM) over the last decade. This paper attempts to offer a bibliographic analysis regarding the current status of applications of two-way coupled models in Asia, related research focuses, model performances, and the effects of ARI and/or ACI on meteorology and air quality. There were a total of 160 peer-reviewed articles published between 2010 and 2019 in Asia meeting the inclusion criteria, with more than 79 % of papers involving the WRF-Chem model. The number of relevant publications has an upward trend annually, and East Asia, India, and China, as well as the North China Plain are the most studied areas. The effects of ARI and both ARI and ACI induced by natural aerosols (particularly mineral dust) and anthropogenic aerosols (bulk aerosols, different chemical compositions, and aerosols from different sources) are widely investigated in Asia. Through the meta-analysis of surface meteorological and air quality variables simulated by two-way coupled models, the model performance affected by aerosol feedbacks depends on different variables, simulation time lengths, selection of two-way coupled models, and study areas. Future research perspectives with respect to the development, improvement, application, and evaluation of two-way coupled meteorology and air quality models are proposed.

Atmospheric aerosols properties over Indo-Gangetic Plain: A trend analysis using ground – Truth AERONET data for the year 2009–2017

The aerosols play an important role in the modification of the regional radiation budget. Long-term trend analysis of properties of atmospheric aerosols is important for policymakers and also for the study of the climatic implications. The Aerosol Robotic Network (AERONET) provides continuous ground-truth aerosol data during cloud-free days since two decades in India. Long-term atmospheric aerosol properties have been studied over four different sites of Indo-Gangetic Plain (IGP): Gandhi College rural background, Kanpur, urban and highly industrial area, Jaipur urban and desert dust influenced region, and Lahore urban and agriculture rich region respectively using AERONET data. The yearly variation of aerosol optical depth (AOD) along with angstrom exponent (AE), single scattering albedo (SSA), size distribution parameters (volume concentration and effective radius), and aerosol radiative forcing (ARF) have been analyzed for nine years from 2009 to 2017. A positive trend of AOD over Kanpur (0.0074/year), a negative trend over Lahore (−0.0054/year), Jaipur – 0.0027/year) and Gandhi college (−0.0008/year) was found. Volume concentration shows the increasing trend of fine mode particles which may be due to increased anthropogenic activities in comparison to natural aerosols over Kanpur, Lahore, Gandhi College, and Jaipur respectively. SSA values over Kanpur and Jaipur show dominancy of scattering while absorbing nature of particles over Lahore and Gandhi College were found. The trend of total atmospheric radiative forcing (ARF ATM ) over Kanpur and Jaipur locations was found to be decreased slightly but not so significantly while over Lahore and Gandhi College trend was found to increase in a significant way. The yearly trend of ARF ATM over Kanpur, Lahore, Jaipur, and Gandhi College was found to be −0.76 Wm −2 /year, 2.22 Wm −2 /year, −0.08 Wm −2 /year, and 3.09 Wm −2 /year respectively.

A global land aerosol fine-mode fraction dataset (2001–2020) retrieved from MODIS using hybrid physical and deep learning approaches

Abstract. The aerosol fine-mode fraction (FMF) is valuable for discriminating natural aerosols from anthropogenic ones. However, most current satellite-based FMF products are highly unreliable over land. Here, we developed a new satellite-based global land daily FMF dataset (Phy-DL FMF) by synergizing the advantages of physical and deep learning methods at a 1∘ spatial resolution covering the period from 2001 to 2020. The Phy-DL FMF dataset is comparable to Aerosol Robotic Network (AERONET) measurements, based on the analysis of 361 089 data samples from 1170 AERONET sites around the world. Overall, Phy-DL FMF showed a root-mean-square error (RMSE) of 0.136 and correlation coefficient of 0.68, and the proportion of results that fell within the ±20 % expected error (EE) envelopes was 79.15 %. Moreover, the out-of-site validation from the Surface Radiation Budget (SURFRAD) observations revealed that the RMSE of Phy-DL FMF is 0.144 (72.50 % of the results fell within the ±20 % EE). Phy-DL FMF showed superior performance over alternative deep learning or physical approaches (such as the spectral deconvolution algorithm presented in our previous studies), particularly for forests, grasslands, croplands, and urban and barren land types. As a long-term dataset, Phy-DL FMF is able to show an overall significant decreasing trend (at a 95 % significance level) over global land areas. Based on the trend analysis of Phy-DL FMF for different countries, the upward trend in the FMFs was particularly strong over India and the western USA. Overall, this study provides a new FMF dataset for global land areas that can help improve our understanding of spatiotemporal fine-mode and coarse-mode aerosol changes. The datasets can be downloaded from https://doi.org/10.5281/zenodo.5105617 (Yan, 2021).

Establishing a non-hydrostatic global atmospheric modeling system at 3-km horizontal resolution with aerosol feedbacks on the Sunway supercomputer of China

During the era of global warming and highly urbanized development, extreme and high impact weather as well as air pollution incidents influence everyday life and might even cause the incalculable loss of life and property. Despite the vast development of atmospheric models, there still exist substantial numerical forecast biases objectively. To accurately predict extreme weather, severe air pollution, and abrupt climate change, numerical atmospheric model requires not only to simulate meteorology and atmospheric compositions simultaneously involving many sophisticated physical and chemical processes but also at high spatiotemporal resolution. Global integrated atmospheric simulation at spatial resolutions of a few kilometers remains challenging due to its intensive computational and input/output (I/O) requirement. Through multi-dimension-parallelism structuring, aggressive and finer-grained optimizing, manual vectorizing, and parallelized I/O fragmenting, an integrated Atmospheric Model Across Scales (iAMAS) was established on the new Sunway supercomputer platform to significantly increase the computational efficiency and reduce the I/O cost. The global 3-km atmospheric simulation for meteorology with online integrated aerosol feedbacks with iAMAS was scaled to 39,000,000 processor cores and achieved the speed of 0.82 simulation day per hour (SDPH) with routine I/O, which enabled us to perform 5-day global weather forecast at 3-km horizontal resolution with online natural aerosol impacts. The results demonstrate the promising future that the increasing of spatial resolution to a few kilometers with online integrated aerosol feedbacks may significantly improve the global weather forecast.

Pan-Arctic seasonal cycles and long-term trends of aerosol properties from 10 observatories

Abstract. Even though the Arctic is remote, aerosol properties observed there are strongly influenced by anthropogenic emissions from outside the Arctic. This is particularly true for the so-called Arctic haze season (January through April). In summer (June through September), when atmospheric transport patterns change, and precipitation is more frequent, local Arctic sources, i.e., natural sources of aerosols and precursors, play an important role. Over the last few decades, significant reductions in anthropogenic emissions have taken place. At the same time a large body of literature shows evidence that the Arctic is undergoing fundamental environmental changes due to climate forcing, leading to enhanced emissions by natural processes that may impact aerosol properties. In this study, we analyze 9 aerosol chemical species and 4 particle optical properties from 10 Arctic observatories (Alert, Kevo, Pallas, Summit, Thule, Tiksi, Barrow/Utqiaġvik, Villum, and Gruvebadet and Zeppelin Observatory – both at Ny-Ålesund Research Station) to understand changes in anthropogenic and natural aerosol contributions. Variables include equivalent black carbon, particulate sulfate, nitrate, ammonium, methanesulfonic acid, sodium, iron, calcium and potassium, as well as scattering and absorption coefficients, single scattering albedo and scattering Ångström exponent. First, annual cycles are investigated, which despite anthropogenic emission reductions still show the Arctic haze phenomenon. Second, long-term trends are studied using the Mann–Kendall Theil–Sen slope method. We find in total 41 significant trends over full station records, i.e., spanning more than a decade, compared to 26 significant decadal trends. The majority of significantly declining trends is from anthropogenic tracers and occurred during the haze period, driven by emission changes between 1990 and 2000. For the summer period, no uniform picture of trends has emerged. Twenty-six percent of trends, i.e., 19 out of 73, are significant, and of those 5 are positive and 14 are negative. Negative trends include not only anthropogenic tracers such as equivalent black carbon at Kevo, but also natural indicators such as methanesulfonic acid and non-sea-salt calcium at Alert. Positive trends are observed for sulfate at Gruvebadet. No clear evidence of a significant change in the natural aerosol contribution can be observed yet. However, testing the sensitivity of the Mann–Kendall Theil–Sen method, we find that monotonic changes of around 5 % yr−1 in an aerosol property are needed to detect a significant trend within one decade. This highlights that long-term efforts well beyond a decade are needed to capture smaller changes. It is particularly important to understand the ongoing natural changes in the Arctic, where interannual variability can be high, such as with forest fire emissions and their influence on the aerosol population. To investigate the climate-change-induced influence on the aerosol population and the resulting climate feedback, long-term observations of tracers more specific to natural sources are needed, as well as of particle microphysical properties such as size distributions, which can be used to identify changes in particle populations which are not well captured by mass-oriented methods such as bulk chemical composition.

Impact of the Coarse Indoor Non-radioactive Aerosols on the Background Radon Progenies' Compensation of a Continuous Air Monitor.

This paper addresses the problem of false positive alarm when using a continuous air monitor (CAM) in decommissioning sites of nuclear facilities. CAMs are used to measure airborne activity and play an important role in the radiation protection of workers likely to be exposed to radioactive aerosols. Monitors usually sample aerosols on a membrane filter. Radioactive particles sampled are detected through the alpha and beta decays that they emit. These latter ionizing particles are measured online by spectrometry thanks to a Passivated Implanted Planar Silicon detector (PIPS). Alpha and beta decays, in this context, come mainly from the natural radon progeny (218Po, 214Pb, and so on) and, in the case of radioactive contamination, also from artificial radionuclides such as 239Pu or 137Cs. The aim of the CAM is to alert the workers when the artificial airborne activity occurs, always considering the presence of a variable background due to the natural particulate airborne activity. The CAM-specific algorithm considers this background dynamically and continuously, often by using a constant parameter. However, non-radioactive aerosols are also sampled on the membrane filter. These latter make the discrimination more difficult as they lead to the deterioration of the alpha-energy spectrum. In this paper, the effect of coarse non-radioactive aerosols on the CAM response is highlighted with four aerosol size-distributions. The evolution of the background is characterized as a function of the aerosol mass sampled, with the example of a simple algorithm. Thus, in this paper, results show a positive correlation of the background with the aerosol mass sampled by the CAM. In addition, results highlight at least two different evolutionary trends according to the aerosol size distribution. An explanation of these evolutions is given by considering the penetration profile of the natural radioactive aerosols in the granular deposit above the CAM filter. The main consequence of these results is that the background could not be considered as proportional to radon progeny as it is currently used.

A dark target Kalman filter algorithm for aerosol property retrievals in urban environment using multispectral images

Natural and anthropogenic aerosol atmospheric emissions play a fundamental role in directly modulating the incoming solar radiation and affecting the air quality, especially in large metropolitan regions. Likewise, aerosols indirectly impact cloud lifetime, atmospheric column thermodynamics and precipitation patterns. For these reasons, it is of particular importance to assess the aerosol spatial and temporal variability in the first instance to reduce the associated global climate models uncertainty to correctly forecasting future scenarios and then to react fast in applying mitigation strategies. In this paper, an aerosol optical depth (AOD) retrieval algorithm for high-spatial resolution images in the blue wavelength range for urban environments is developed for the first time. The proposed approach is completely blind because does not use look-up-tables or complex radiative transfer models, which require the setting/estimation of many parameters. The multi-wavelength (exploiting the coastal and the blue bands) AOD retrieval permits to retrieve also important aerosol micro-physical properties, e.g., the size. The proposed method leverages on the use of Kalman filters to deal with the unavoidable sensor's noise improving the accuracy of the estimation of the AOD. The approach is assessed on four different test cases acquired by Landsat 8 involving two metropolitan areas. A strong agreement to ground-based AERONET measurements is observed on several performance metrics. Clear advantages in comparison with the baseline approach relied upon the simple inversion of the explored model are pointed out.

The significant impact of shape deviations of atmospheric aerosols on light monitoring networks

ABSTRACT Aerosol particles are important modulators of night sky brightness (NSB) due to their manifold impacts on spectral and angular properties of scattered light. The majority of radiative transfer models currently in use are based on rigorous Mie theory for spherical homogeneous particles. This fundamental concept enables significant simplifications in theoretical formulae and numerical modelling. However, as known from many studies, spherical shapes are rare for both natural and anthropogenic aerosols. Therefore, the aim of this paper is to analyse the potential magnitude of the subsequent effect in skyglow modelling assuming that the aerosol particles are of different aspect ratios. The zero-order approximation to tackle the problem is to characterize the non-sphericity by the ratio of the largest to smallest size of an ellipsoidal particle. We use T-matrix formalism to perform light scattering calculations on spheroidal particles of arbitrary size, composition, and orientation in respect to the incident light. Results indicate that the particle-shape impact on NSB can be of significant size leading to both positive and negative amplitudes around the zenith. In the most extreme case, an increase of up to 70 per cent in zenithal luminance was displayed. As a consequence, especially light monitoring devices like the sky quality meter, usually measuring the NSB around the zenith, are particularly influenced by this effect. In summary, the paper underlines both the importance of treating non-spherical aerosols in theoretical modelling of skyglow and also the significance of including atmospheric parameters to analyses of light monitoring networks.