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aerosols enhance cloud lifetime and brightness along the stratus-to-cumulus transition

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2020年第30期117卷 17591-17598页

作者： Christensen, Matthew W. Jones, William K. Stier, Philip Univ Oxford Atmospher Ocean & Planetary Phys Oxford OX1 3PU England

Anthropogenic aerosols are hypothesized to enhance planetary albedo and offset some of the warming due to the buildup of greenhouse gases in Earth's atmosphere. aerosols can enhance the coverage, reflectance, and lifetime of warm low-level clouds. However, the relationship between cloud lifetime and aerosol concentration has been challenging to measure from polar orbit-ing satellites. We estimate two timescales relating to the for-mation and persistence of low-level clouds over 1 degrees x 1 degrees spatial domains using multiple years of geostationary satellite observa-tions provided by the Clouds and Earth's Radiant Energy System (CERES) Synoptic (SYN) product. Lagrangian trajectories span-ning several days along the classic stratus-to-cumulus transition zone are stratified by aerosol optical depth and meteorology. Clouds forming in relatively polluted trajectories tend to have lighter precipitation rates, longer average lifetime, and higher cloud albedo and cloud fraction compared with unpolluted tra-jectories. While liquid water path differences are found to be negligible, we find direct evidence of increased planetary albedo primarily through increased drop concentration (Nd) and cloud fraction, with the caveat that the aerosol influence on cloud fraction is positive only for stable atmospheric conditions. While the increase in cloud fraction can be large typically in the beginning of trajectories, the Twomey effect accounts for the bulk (roughly 3/4) of the total aerosol indirect radiative forcing estimate.

关键词： aerosols clouds radiative forcing

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Possible, impossible, and expected diameters and production rates of droplets in aerosols and sprays

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Physical Review Fluids 2022年第6期7卷 063602-063602页

作者： Maksim Mezhericher Howard A. Stone Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544 USA

Liquid atomization processes generating sprays and aerosols of droplets are used in many delivery and coating systems involving pure solvents, solutions, and suspensions. In our recent experimental work, we introduced a novel liquid atomization process generating microsprays and aerosols of submicron-diameter droplets for pure solvents, solutions, and suspensions: gas jets disintegrate thin liquid films that are formed as bubbles approach a liquid surface. Here, we develop a theoretical description of droplet sizes and flow rates, using the first principles of conservation of mass and energy, and employing dimensional and scale analyses. We introduce atomization diagrams as a graphical tool to determine possible, impossible, and expected droplet diameters and specific flow rates in aerosols and sprays produced under various conditions. We find a reasonable agreement between the theory and experiments for five different liquids converted into aerosols of submicron-diameter droplets by an atomization process where gas jets disintegrate thin liquid films that are formed as bubbles approach a liquid surface, and also for five traditional pressure nozzles that produce sprays of droplets of hundreds of microns in diameter. Our study explores the overall range of mean droplet diameters between 0.1 and 100 μm and Ohnesorge numbers between 0.01 and 100, and the analysis and atomization diagrams contribute to understanding of liquid atomization and can serve as a theoretical framework for comparing different liquid atomization techniques.

关键词： Drop & bubble phenomena Surface tension effects Thermodynamics Thin fluid films Wakes & jets aerosols Drops & bubbles

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Meso-scale numerical analysis for transport and deposition behaviors of radioactive aerosols under severe nuclear accident

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PROGRESS IN NUCLEAR ENERGY 2022年 150卷

作者： Ma, Zhenhui Ma, Tengyue Wang, Baosheng Li, Da Su, Chunlei Liu, Longbo Hu, Pan Li, Zhiming Chen, Lixin Tang, Xiuhuan Northwest Inst Nucl Technol Xian 710024 Peoples R China

Radioactive aerosols would be released to the atmosphere during severe nuclear accidents. Depending on local meteorological condition, aerosols would be transported to downwind area of nuclear site and fell to the ground simultaneously. Such behaviors may cause heavy contamination to the environment, and even bring damage to local residents. Therefore, theoretical study for aerosols transport and deposition is very meaningful in severe nuclear accident research. In the present study, calculation method for 3D aerosols transport and deposition simulation was established based on WRF-CMAQ model. Datasets for meteorological field would be acquired by WRF for aerosols transport simulation. Besides, to perform parameterization for aerosols source term, selfcompiled module RAMS was applied to create source term file. Based on such calculation method, transport and deposition for aerosols can be simulated numerically, distribution for aerosols concentration, aerosols deposition flux and contaminated area were analyzed in detail. Besides, different monitoring locations were selected for parameter comparison. The present theoretical research for aerosols transport and deposition simulation is essential for nuclear accident research and will lay a solid foundation for safety assessment and aftermath evaluation.

关键词： Nuclear accident aerosols Transport Deposition Meteorology

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Is the atmospheric boundary layer altitude or the strong thermal inversions that control the vertical extent of aerosols?

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SCIENCE OF THE TOTAL ENVIRONMENT 2022年 802卷 149758-149758页

作者： Prasad, P. Basha, Ghouse Ratnam, M. Venkat Natl Atmospher Res Lab NARL Gadanki India

It is well known that the atmospheric boundary layer (ABL) plays a significant role in controlling the variability of atmospheric constituents such as aerosols and trace-gases. Hence, significant diurnal and seasonal variation in these will be observed as the ABL altitude does. However, on several occasions, high aerosol concentration in the lidar measurements is observed even above the ABL altitude. This raised a question that up to what extent ABL altitude acts as a capping layer for these pollutants? From the detailed analysis carried out using long-term (2010-2018) lidar observations and simultaneous radiosonde profiles obtained from Gadanki, India, we show that 'there exist thermal inversions (TI), which are stronger than the ABL inversions, that fully control the vertical extent'. The detailed characteristics of TI (inversion strength (IS) and inversion depth (ID)) are also obtained. The results revealed that aerosol concentrations below the TI altitude increases with IS (ID) up to 3-4 K (300-400 m) during winter whereas in pre-monsoon it increases up to 2-3 K (100-200 m). Thus, IS of up to 2-4 K is required to fully trap the aerosol concentrations and this TI coincide with the ABL inversions for 51.7% only, particularly during the winter and pre-monsoon seasons. This analysis is further extended to different geographical locations of India using the aerosol profiles obtained from CALIPSO and a network of 23 radiosonde stations. The observed results provided further evidence that the vertical distribution of aerosols is restricted to the maximum extent by the TI but not the ABL altitude. These observations lead us to propose a hypothesis that 'trapping of aerosols fully occurs up to particular IS and ID only and the ABL altitude is not the deciding factor most of the time for capping the aerosol vertical distribution'. These findings will greatly help in modeling the dif-fusion and transport of air pollutants in the lower troposphere. (c) 2021 Elsevier B.V. Al

关键词： aerosols Temperature inversion Boundary layer height AOD

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Climatic Factors of the Radionuclide Composition of Atmospheric aerosols in Rostov-on-Don

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ATMOSPHERIC AND OCEANIC OPTICS 2021年第1期34卷 14-18页

作者： Mikhailova, T. A. Kaschaeva, E. A. Masharov, K. S. Buraeva, E. A. Popov, Yu, V Verbenko, I. A. Southern Fed Univ Res Inst Phys Rostov Na Donu 344090 Russia Southern Fed Univ Dept Phys Rostov Na Donu 344090 Russia Southern Fed Univ Inst Earth Sci Rostov Na Donu 344090 Russia

We present the results of the study of the radionuclide composition of atmospheric aerosols and seasonal behavior of pollutants in the surface air layer in Rostov-on-Don, which is located in the steppe zone. The data were obtained from the study of atmospheric aerosol samples taken in 2001-2009. The volumetric activity of radionuclides was measured using the gamma-spectrometric radionuclide analysis. The spring-summer maxima and autumn-winter minima were revealed in the seasonal behavior of the volumetric activity of radionuclides in the atmosphere caused by changes in weather parameters. According to the radionuclide air pollution index, the highest degree of radiation hazard for the city is associated with the product of Rn-222-Pb-210 decay. The special significance of Cs-137 as a potentially dangerous radionuclide in the case of a large-scale nuclear accident is noted.

关键词： aerosols radionuclides heavy metals

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A Novel Design Strategy to Confine the Transmission of Exhaled aerosols: An Integrated Experimental-Numerical Investigation

SSRN

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SSRN 2023年

作者： Wang, Yongxin Liu, Zhijian Liu, Haiyang Xiao, Xia He, Junzhou Li, Shiyue Liang, Zhenyu Department of Power Engineering North China Electric Power University Beijing071003 China The State Key Laboratory of Respiratory Disease Guangzhou Institute of Respiratory Health the First Affiliated Hospital of Guangzhou Medical University Guangzhou510120 China

The partition is a device that can effectively suppress the spread of aerosols. It has been widely used in public places such as restaurants and shopping malls during the COVID-19 pandemic. Inspired by that, this study explored a strategy for setting up partial partitions in negative pressure isolation wards to limit the diffusion of bioaerosol. In this study, Serratia marcescens was used as bioaerosol releasing material to study the bioaerosol distribution. Computational fluid dynamics method was used to further explore the interrupted effect of five partition strategies on aerosol diffusion in the isolation ward. The flow patterns in the ward and the spatiotemporal distribution of aerosols were obtained and analyzed. The results showed that the best strategy could increase bioaerosol removal effectiveness index from 0.569 to 0.696, which accelerated the bioaerosol removal. Only selecting a reasonable size and installation position, can the partial partition play a positive role in the interruption of aerosol diffusion. Moreover, small-area partial partition can achieve efficient control of bioaerosol diffusion as well. This study could provide reference for the design of isolation wards or the optimization and renovation of isolation wards. © 2023, The Authors. All rights reserved.

关键词： aerosols

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Secondary Inorganic aerosols and Aerosol Acidity at Different Pm2.5 Pollution Levels During Winter Haze Episodes in the Sichuan Basin, China

SSRN

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SSRN 2023年

作者： Fu, Xiaoxin Wang, Xinming Liu, Tengyu He, Quanfu Zhang, Zhou Zhang, Yanli Song, Wei Dai, Qunwei Chen, Shu Dong, Faqin Key Laboratory of Solid Waste Treatment and Resource Recycle Ministry of Education Southwest University of Science and Technology Mianyang621010 China State Key Laboratory of Organic Geochemistry Guangdong Key Laboratory of Environmental Protection and Resources Utilization Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou510640 China Joint International Research Laboratory of Atmospheric and Earth System Sciences School of Atmospheric Sciences Nanjing University Nanjing210023 China Institute for Energy and Climate Research IEK-8 Forschungszentrum Jülich Jülich52425 Germany

Wintertime fine particle (PM2.5) pollution remains to be perplexing air quality problems in many parts of China. In this study, PM2.5 compositions and aerosol acidity at different pollution levels at an urban cite in the southwest China’s Sichuan Basin were investigated during a sustained winter haze *** matter was the most abundant component of PM2.5, followed by nitrate, sulfate and and ammonium. Shares of organic aerosol in PM2.5 mass decreased with the elevated PM2.5 levels, while the enhancements of sulfate and secondary organic aerosol were much less than that of nitrate and ammonium during heavy pollution with increased ratios of nitrate to sulfate, implying a significant role of nitrate in the haze formation. Results also suggest the nighttime chemistry might contribute substantially to the formation of nitrate under severe pollutions. The daily average aerosol pH showed a decreasing trend with the elevated levels of PM2.5, and this increased aerosl acidity was mainly due to the fast rising secondary inorganic aerosol (SIA) concentration, with the increase in hydronium ion concentration in air (Hair+) surpassing the dilution effect of elevated aerosol liquid water content (LWC). Thermodynamic model calculations revealed that the air environment was NH3-rich with total NHx (NH3+NH4+) greater than required NHx, and the aerosol pH exponentially declined with the decreasing excess NHx (p＜0.01). This study demonstrated that under air stagnation and NH3-rich environment during winter, the raised relative humidity (RH) would lead to an increase in LWC and thereby facilitate the aqueous chemistry processes with the neutralization capacity of NH3 to form sulfate and nitrate, which would further increase the LWC and lower the pH. This self-amplifying SIA formation might be crucial to the severe PM2.5 pollution and haze events during winter, and therefore cutting both NOx and NH3 emissions would benefit stopping the self-amplification. © 2023, The Authors.

关键词： aerosols

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Warm-phase spectral-bin microphysics in ICON: reasons of sensitivity to aerosols

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ATMOSPHERIC RESEARCH 2022年 279卷

作者： Khain, Pavel Shpund, Jacob Levi, Yoav Khain, Alexander Israeli Meteorol Serv Bet Dagan Israel Pacific Northwest Natl Lab Richland WA 99352 USA Hebrew Univ Jerusalem Jerusalem Israel

The warm-phase version of the Spectral-Bin Microphysics (SBM) scheme has been implemented into the ICON model and has been tested in a supercell storm simulation. The results of two-moment (2M) bulk scheme which exists in ICON and SBM were compared in all aspects related to warm processes, especially with regards to sensitivity to aerosols. In all simulations a strong storm with maximum updrafts exceeding 25 m/s was simulated. The maximum vertical velocity in the 2M bulk scheme does not depend on aerosols. However, the maximum vertical velocity in SBM with high aerosol concentration was found substantially higher than in the case of low aerosol concentration. Despite the insensitivity of maximum vertical velocity to aerosols, the microphysics of the 2M scheme is sensitive to aerosols. Both SBM and 2M schemes showed faster rain formation in case of low aerosol concen-tration;both schemes indicate that first raindrops form when the mean volume radius exceeds ~15 mu m. In both schemes the first raindrops form near cloud top in an undiluted core and fall along the cloud edges at the mature stage. At the decaying stage, raindrops fall through the cloud core. The zone of rainfall at the lower few kilo-meters coincides with the zones of strong downdrafts. A substantial effect of aerosols on intensity and spatial distribution of precipitation was found. In the case of low aerosol concentration raindrops form earlier and at lower altitudes. As a result, the area covered by rain is lower, but the maximum of the rain intensity is higher than in case of high aerosol concentration. Finally, we discuss the hindering effects of large supersaturation via mass loading on the cloud development in case of low aerosol concentration, and examine the validity of the well-known saturation adjustment procedure.

关键词： Numerical modelling Cloud microphysics Spectral bin microphysics aerosols Precipitation

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15-Year Analysis of Direct Effects of Total and Dust aerosols in Solar Radiation/Energy over the Mediterranean Basin

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REMOTE SENSING 2022年第7期14卷 1535页

作者： Papachristopoulou, Kyriakoula Fountoulakis, Ilias Gkikas, Antonis Kosmopoulos, Panagiotis G. Nastos, Panagiotis T. Hatzaki, Maria Kazadzis, Stelios Natl & Kapodistrian Univ Athens LACAE NKUA Dept Geol & Environm Sect Geog & Climatol Lab Climatol & Atmospher Environm Athens 15784 Greece Natl Observ Athens IAASARS NOA Inst Astron Astrophys Space Applicat & Remote Sen Athens 15236 Greece World Radiat Ctr Phys Meteorol Observatorium Davos CH-7260 Davos Switzerland Natl Observ Athens IERSD NOA Inst Environm Res & Sustainable Dev Athens 15236 Greece

The direct radiative effects of atmospheric aerosols are essential for climate, as well as for other societal areas, such as the energy sector. The goal of the present study is to exploit the newly developed ModIs Dust AeroSol (MIDAS) dataset for quantifying the direct effects on the downwelling surface solar irradiance (DSSI), induced by the total and dust aerosol amounts, under clear-sky conditions and the associated impacts on solar energy for the broader Mediterranean Basin, over the period 2003-2017. Aerosol optical depth (AOD) and dust optical depth (DOD) derived by the MIDAS dataset, along with additional aerosol and dust optical properties and atmospheric variables, were used as inputs to radiative transfer modeling to simulate DSSI components. A 15-year climatology of AOD, DOD and clear-sky global horizontal irradiation (GHI) and direct normal irradiation (DNI) was derived. The spatial and temporal variability of the aerosol and dust effects on the different DSSI components was assessed. Aerosol attenuation of annual GHI and DNI were 1-13% and 5-47%, respectively. Over North Africa and the Middle East, attenuation by dust was found to contribute 45-90% to the overall attenuation by aerosols. The GHI and DNI attenuation during extreme dust episodes reached 12% and 44%, respectively, over particular areas. After 2008, attenuation of DSSI by aerosols became weaker mainly because of changes in the amount of dust. Sensitivity analysis using different AOD/DOD inputs from Copernicus Atmosphere Monitoring Service (CAMS) reanalysis dataset revealed that using CAMS products leads to underestimation of the aerosol and dust radiative effects compared to MIDAS, mainly because the former underestimates DOD.

关键词： aerosols dust direct radiative effects solar energy Mediterranean Basin

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Interannual crisscross pattern observed in South Asian monsoon rainfall and its relationship with aerosols

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ATMOSPHERIC RESEARCH 2022年 271卷

作者： Raja, Boragapu Maheskumar, R. S. Padmakumari, B. Devi, S. Sunitha Indian Inst Trop Meteorol Dr Homi Bhabha Rd Pune 411008 Maharashtra India Savitribai Phule Pune Univ Dept Atmospher & Space Sci Ganeshkhind Rd Pune 411008 Maharashtra India Minist Earth Sci Lodhi Rd New Delhi 110003 India Indian Meteorol Dept Lodhi Rd New Delhi 110003 India Indian Meteorol Dept Pune 411005 Maharashtra India

This study examines the interannual variability of South Asian summer monsoon rainfall (SAMR) using a linear trend analysis for the recent 17-year period from 2000 to 2016. The trends in SAMR analyzed from multiple rainfall datasets show a unique crisscross like pattern over South Asia and its surrounding oceans. Significant positive trends in SAMR occur over the middle and south Bay of Bengal (BOB) and North-West India (NWI) aligned in SE-NW direction. Similarly, significant negative trends are observed over North-East India and head Bay of Bengal (NEI) as well as over the middle and south Arabian Sea (AS) oriented in SW-NE direction. Western Ghats make an exception to this pattern, where significant positive trends have been observed. Interestingly, the trends in aerosol optical depth (AOD) for the same period closely follow the trends in SAMR. The relationship of AOD averaged over each of the significant aerosol trend regions with the SAMR suggest aerosol induced suppression in moisture transport from a region covering Southern Arabian Sea and Bay of Bengal played a dominant role over the negative trend regions. However, the decreased aerosols over the Northwest India due to significant positive trends in rainfall reduced dust transport from the Arabian Peninsula towards eastern parts of South Asia resulting in an increase in anthropogenic aerosols from local sources. This caused significant drying over the NEI and AS regions through aerosol indirect effects. Further, Aerosol direct radiative effects due to natural and anthropogenic sources inferred from the climate forcing estimates confirmed their role in positive trends and the indirect effects inferred from satellite cloud products depicted a strong association with negative trends, thus maintaining the observed crisscross pattern.

关键词： aerosols Crisscross Pattern South Asian summer monsoon rainfall Interannual variability

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