Aerosol Properties Research Articles

The Ability of Vaping Technology to Deliver an Equivalent Respirable Dose of Beclomethasone Dipropionate Compared to Nebulization

Background/Objectives: This study focuses on the ability of vaping technology to deliver beclomethasone dipropionate compared to nebulization. Methods: An in vitro comparison of aerosol properties in terms of respirable dose with the Glass Twin Impinger and the mass median aerodynamic diameter using the Next Generation Impactor was performed. The respirable dose delivered in a vaping drug delivery system (VDDS) puff as a function of concentration was quantified by high-pressure liquid chromatography coupled with an ultraviolet detector. Results: The mass of drug contained in a single puff of 55 mL of aerosol varied between 0.94 and 1.95 µg for a refill liquid concentration range of 400 to 1600 µg/mL. The analysis of the particle size distribution shows an advantage for a VDDS in producing smaller particles compared to nebulization (1.56 ± 0.05 µm vs. 2.30 ± 0.19 µm). In total, 81 puffs are needed to reach the dose equivalent to nebulized beclomethasone dipropionate under these specific experimental conditions, which corresponds to an aerosol duration of about 4 min (i.e., four times lower than the jet nebulizer) and a patient administration time of about 45 min (i.e., three times higher than the jet nebulizer). Conclusions: The results show the potential of vaping devices as an alternative to nebulizers for the administration of beclomethasone dipropionate in an equivalent respirable dose.

TEOS-10 and the climatic relevance of ocean–atmosphere interaction

Abstract. Unpredicted observations in the climate system, such as recent excessive ocean warming, are often lacking immediate causal explanations and are challenging numerical models. As a highly advanced mathematical tool, the Thermodynamic Equation of Seawater – 2010 (TEOS-10) was established by international bodies as an interdisciplinary standard and is recommended for use in geophysics, such as, and in particular, in climate research. From its very beginning, the development of TEOS-10 was supported by Ocean Science through publishing successive stages and results. Here, the history and properties of TEOS-10 are briefly reviewed. With focus on the air–sea interface, selected current problems of climate research are discussed, and tutorial examples for the possible use of TEOS-10 in the associated context are presented, such as topics related to ocean heat content, latent heat, and the rate of marine evaporation; properties of sea spray aerosol; or climatic effects of low-level clouds. Appended to this article, a list of publications and their metrics is provided for illustrating the uptake of TEOS-10 by the scientific community, along with some continued activities, addressing still pending, connected issues such as uniform standard definitions of uncertainties of relative humidity, seawater salinity, or pH. This article is dedicated to the jubilee celebrating 20 years of Ocean Science. This article is also dedicated to the memory of Wolfgang Wagner, who sadly and unexpectedly passed away on 12 August 2024. His contributions to TEOS-10 are truly indispensable constituents; Wolfgang was an essential co-author of various related documents and articles. He will be deeply missed. All the rivers run into the sea; yet the sea is not full; unto the place from whence the rivers come, thither they return again. The King James Bible: Ecclesiastes, 450–150 BCE He wraps up the waters in his clouds, yet the clouds do not burst under their weight. Holy Bible: New International Version, Job 26:8 Of the air, the part receiving heat is rising higher. So, evaporated water is lifted above the lower air. Leonardo da Vinci: Primo libro delle acque, Codex Arundel, ca. 1508 Two-thirds of the Sun's energy falling on the Earth's surface is needed to vaporize … water … as a heat source for a gigantic steam engine. Heinrich Hertz: Energiehaushalt der Erde, 1885 The sea-surface interaction is obviously a highly significant quantity in simulating climate. Andrew Gilchrist and Klaus Hasselmann: Climate Modelling, 1986 The climate of the Earth is ultimately determined by the temperatures of the oceans. Donald Rapp: Assessing Climate Change, 2014

Comparative analysis of cloud properties over drought- and flood-prone regions of western India using machine learning techniques

ABSTRACT Cloud properties are pivotal in analyzing rainfall patterns globally, especially in monsoon-dependent countries such as India. The impact of climate change becomes more important in regions susceptible to hydrometeorological events due to different monsoon regimes. To examine regional heterogeneity of cloud properties, this study investigates long-term trends and predictive capabilities for cloud properties in drought-prone and flood-prone regions of western India, utilizing satellite data and employing various machine learning (ML) models to comprehend intricate data patterns and enhance predictive accuracy. The results show higher mean and variability in cloud parameters over the flood-prone area due to favorable rain conditions, reflecting higher cloud microphysical and optical properties. These parameters negatively correlate with some cloud macrophysical properties along with the aerosol property in the drought-prone area. Additionally, a moderate correlation exists between certain cloud characteristics of one region and another. Employing ML algorithms for regression analysis and comparing them for cloud effective radius across regions shows promising results, with random forest (RF) demonstrating high coefficient of determination (0.86, 0.93) and low root mean squared error (0.76, 1.15) due to its robustness and high accuracy. This research enhances the understanding of regional heterogeneity in India and shows that ML can be helpful in predicting future cloud dynamics and climate variables identifying the most suitable model.

ALICENET – an Italian network of automated lidar ceilometers for four-dimensional aerosol monitoring: infrastructure, data processing, and applications

Abstract. ​​​​​​​Vertically resolved information on aerosol particles represents a key aspect in many atmospheric studies, including aerosol–climate interactions and aerosol impacts on air quality and human health. This information is primarily derived by lidar active remote sensing, in particular with extensive networks currently in operation worldwide. In Italy, the Institute of Atmospheric Sciences and Climate (ISAC) of the National Research Council (CNR) established the ALICENET network of automated lidar ceilometers (ALCs) in 2015. Since then, ALICENET has grown as a cooperative effort of Italian institutions dealing with atmospheric science and monitoring, and it currently includes instruments run by regional environmental protection agencies, universities, research centres, and private companies. In the current configuration, the network makes use of both single-channel ALCs and dual-channel, polarisation-sensitive-system ALCs (referred to as PLCs). The systems operate in very different environments (urban, coastal, mountainous, and volcanic areas) from northern to southern Italy, thus allowing the continuous monitoring of the aerosol vertical distribution across the country. ALICENET also contributes to the EUMETNET programme E-PROFILE, filling an Italian observational gap compared to other EU member states, which generally run extended ALC networks through national meteorological services. In this work, we present the ALICENET infrastructure and the specifically developed data processing centralised at CNR-ISAC, converting raw instrumental data into quantitative, quality-controlled information on aerosol properties ranging from attenuated backscatter to aerosol mass and vertical stratifications. This setup allows us to get insights into the 4D aerosol field over Italy with applications from near-real-time monitoring to long-term analyses, examples of which are reported in this work. Specific comparisons of the ALICENET products to independent measurements obtained with different techniques, such as particulate matter (PM) concentrations from in situ samplers and aerosol optical depth (AOD) from sun photometers, are also included here, revealing the good performances of the ALICENET algorithms. Overall, ALICENET represents a valuable resource to extend the current aerosol observational capabilities in Italy and in the Mediterranean area, and it contributes to bridging the gap between atmospheric science and its application to specific sectors, among which are air quality, solar energy, and aviation safety.

Исследование методов и современных технических решений очистки аэрозольных выбросов промышленности

The analysis and characterization of aerosol emissions into the atmosphere are given, the ways of formation of primary and secondary aerosols are considered. The process of atmospheric aging of aerosols, which has a negative impact on the environment, is considered. The functional links between aerosol emissions, their source and impact on climate and public health are presented. The possible influence of the reactions of liquid and solid aerosol particles on the properties of atmospheric air is considered. The main methods of purification of industrial aerosol emissions are considered: adsorption purification, thermal and catalytic neutralization, chemisorption and absorption purification. The ways of increasing the efficiency of adsorption processes, for example, the separation of adsorbent in the apparatus, are analyzed. The essence of the process of thermal neutralization of gas mixtures is described, it is established that thermal installations based on the direct combustion method work more efficiently when combining thermal and catalytic neutralization methods, designs of combined equipment are presented, and ways to increase the intensity of the apparatus are considered. The process of gas purification based on the absorption process is considered. It is determined that absorption plants for cleaning gases from harmful components are the most effective and efficient due to the high level of technical implementation of the process. The development and improvement of the main absorber equipment is aimed at achieving maximum cleaning efficiency with an optimal pressure drop that determines energy consumption. The analysis shows the negative impact of natural and anthropogenic aerosols on the environment. In order to correctly solve the problem, information on the sources, composition and properties of aerosols is needed to select the most effective and economically profitable cleaning method, which will help reduce the anthropogenic load on the atmosphere.

Influence of relative humidity and aging on the optical properties of organic aerosols from burning African biomass fuels

Influence of relative humidity and aging on the optical properties of organic aerosols from burning African biomass fuels

From Polar Day to Polar Night: A Comprehensive Sun and Star Photometer Study of Trends in Arctic Aerosol Properties in Ny-Ålesund, Svalbard

The climate impact of Arctic aerosols, like the Arctic Haze, and their origin are not fully understood. Therefore, long-term aerosol observations in the Arctic are performed. In this study, we present a homogenised data set from a sun and star photometer operated in the European Arctic, in Ny-Ålesund, Svalbard, of the 20 years from 2004–2023. Due to polar day and polar night, it is crucial to use observations of both instruments. Their data is evaluated in the same way and follows the cloud-screening procedure of AERONET. Additionally, an improved method for the calibration of the star photometer is presented. We found out, that autumn and winter are generally more polluted and have larger particles than summer. While the monthly median Aerosol Optical Depth (AOD) decreases in spring, the AOD increases significantly in autumn. A clear signal of large particles during the Arctic Haze can not be distinguished from large aerosols in winter. With autocorrelation analysis, we found that AOD events usually occur with a duration of several hours. We also compared AOD events with large-scale processes, like large-scale oscillation patterns, sea ice, weather conditions, or wildfires in the Northern Hemisphere but did not find one single cause that clearly determines the Arctic AOD. Therefore the observed optical depth is a superposition of different aerosol sources.

Measurement report: In situ vertical profiles of below-cloud aerosol over the central Greenland Ice Sheet

Abstract. Surface radiative cooling in polar regions can generate persistent stability in the atmospheric boundary layer. Stable layers below clouds can decouple the cloud layer from the near-surface environment. Under these conditions, surface aerosol measurements are not necessarily representative of the near-cloud or intra-cloud aerosol populations. To better understand the variability in the vertical structure of aerosol properties over the central Greenland Ice Sheet, in situ measurements of aerosol particle size distributions up to cloud base were made at Summit Station in July and August 2023. These measurements identified distinct vertical aerosol layers between the surface- and cloud-base-associated thermodynamic decoupling layers. Such decoupling layers occur 49 % of the time during the summer in central Greenland, suggesting that surface aerosol measurements are insufficient for describing the cloud-relevant aerosol population half of the time. Experience during this first measurement season demonstrated the ability of a tethered-balloon platform to operate effectively under icing conditions and at low surface pressure (< 680 hPa). The results presented here illustrate the value of vertically resolved in situ measurements of aerosol properties in developing a nuanced understanding of the aerosol effects on cloud properties in polar regions.

Observational evidence of the association between aerosol properties and lightning characteristics in the Indian subcontinent

Abstract Lightning is a leading cause of natural disaster-related mortality in the Indian Subcontinent. Currently, there is a lack of observational evidence supporting the role of aerosol composition in modulating lightning intensity and trends in this region. In this study, we analyzed satellite and reanalysis datasets to examine the association between aerosol properties and lightning intensity over three contrasting geographic regions of Indian subcontinent during the premonsoon season (1998-2022). By comparing lightning and non-lightning days, we found a 0.1 unit increase in total aerosol optical depth specifically on lightning days in all three study areas. Additionally, we observed that the aerosol composition of a region influences convective activity. The presence of dust alongside fine aerosols acts as efficient ice nuclei, thereby stimulating lightning activity in all three regions. Therefore, considering aerosol composition together with local meteorology is essential for accurately predicting lightning flash rates in a region.

Role of substituent on organosulfate/organosulfonate and amide molecules in the initial stage of atmospheric new particle formation

The role of substituent group in organosulfate/organosulfonate (methanesulfonic acid, methyl hydrogen sulfate and hydroxymethanesulfonic acid) and amides (formamide, acetamide, methylformamidne, and urea) on structure, thermodynamics, intermolecular forces, atmospheric influence and optical properties was studied theoretically. The results show that the substituents can not promote the clustering of rganosulfate/organosulfonate, and can promote the clustering of amides. Additionally, the substituents can improve the optical properties of amide, organosulfate/organosulfonate. Low temperature, high pressure and high altitude contribute to the formation of clusters, and temperature is the dominate factor. Additionally, organic acid promotes the clustering with organosulfate/organosulfonate and amide, and enhances Rayleigh scattering properties, further strengthens the extinction properties of aerosols to affect atmospheric visibility.

Inhalable Dry Powders for Lung mRNA Delivery.

Despite great promise, application of mRNA therapeutics in the lung has proven challenging. Many groups have reported success instilling liquid mRNA formulations in animal models, but direct intratracheal administration of large liquid quantities to the human lung presents significant safety and distribution concerns. To accomplish safe and effective mRNA delivery to the lung, formulations must be prepared for dosing via inhalation. An inhaled mRNA delivery system for the lung must be both robust enough to survive inhalation conditions and potent enough to deliver mRNA upon reaching the lung. In this work dry powder lipid nanoparticle formulations are developed, using spray-freeze-drying, to produce stable, biologically active, inhalable dry powders for mRNA delivery. The final powders have suitable aerosolization properties, with mean mass aerodynamic diameter (MMAD) of 3-4 microns, and fine particle fraction (FPF) ≈40%, allowing for efficient mRNA delivery to the deep lung following inhalation. Importantly, the formulations developed here are suitable for use with different ionizable lipids. Four different ionizable lipid-based formulations are evaluated as powders, and all exhibit in vivo pulmonary mRNA delivery equal to that of instilled liquid formulations. These results lay promising groundwork for the eventual development of an inhalable mRNA dry powder therapeutic.

Design and development of a portable tuneable radiation source from UV to IR for in situ calibration of radiometers measuring atmospheric aerosol properties.

Abstract We present the results of development of a portable tuneable radiation source (TuPS II) covering the broad spectral range from 300 nm up to 1700 nm. It was developed to provide SI-traceable in-situ calibration of bandpass functions of radiometers measuring both sky radiance and sky irradiance in the surface-based remote sensing networks for column integrated atmospheric aerosol properties. The TuPS II provides quasi-monochromatic radiation with spectral bandwidth smaller than 0.2 nm and central wavelength uncertainty lower than 0.05 nm for a specified number of aerosol wavelength bands ranging from to 300 nm to 1700 nm. In its design it represents an evolution with extended spectral capabilities of the TuPS (Smid, M. et al., 2021) that was successfully used to characterize Dobson spectrophotometers in the UV spectral range.

A machine learning paradigm for necessary observations to reduce uncertainties in aerosol climate forcing.

Uncertainties in estimates of climate cooling by anthropogenic aerosols have not decreased significantly in the last two decades, partly because observational constraints on crucial aerosol properties simulated in Earth System Models are insufficient. To help address this insufficiency in aerosol observations, we describe a paradigm for deriving higher-level aerosol properties with machine learning algorithms that use only lidar observations and reanalysis data as predictors. Our paradigm employs high-accuracy suborbital lidar and collocated in situ measurements to train and test two fully-connected neural network algorithms. We use two lidar data sets as input to our machine learning algorithms. The first data set consists of suborbital lidar observations not previously used in the training of the machine learning algorithms. The second data set consists of simulated UV-only observations to preview the algorithms' predictive capabilities in anticipation of data from the ATmospheric LIDar system on the EarthCARE satellite, which was launched in May 2024. Here we show that our algorithms predict two crucial aerosol properties, aerosol light absorption and cloud condensation nuclei concentrations with unprecedented accuracy, yielding mean relative errors of 21% and 13%, respectively, when suborbital lidar data are used as predictors. These errors represent significant improvements over conventional aerosol retrievals. Applied to future satellite missions, the paradigm presented here has great potential for constraining Earth System Models and reducing uncertainties in their estimates of aerosol climate forcing and future global warming.

Carbonaceous aerosol emissions from secondary lighting sources: Emission factors and optical properties

India is shifting towards cleaner residential fuels, but this transition does not fully address household lighting challenges. Power disruptions, especially in rural areas, lead to the use of secondary lighting sources such as kerosene lamps, edible oil lamps, and candles. Our previous work identified kerosene wick and hurricane lamps as major secondary lighting sources in Indian households. This study presents the emission factors (EF) and optical properties of carbonaceous aerosols from five major secondary lighting devices in India, measured using a laboratory extractor hood system. Dominant secondary lighting devices, such as simple wick lamps (61.4 ± 9.8 g kg⁻1) and hurricane lamps (17.2 ± 4.8 g kg⁻1), exhibit higher elemental carbon (EC) EFs than typical residential biomass burning. Sesame oil lamps, primarily used in India during the Diwali festival, also have significant EC emission potential, with an EC EF of 71.6 ± 16.9 g kg⁻1. The low absorption Angstrom exponent (AAE) of ∼1 at near-UV wavelengths indicates a dominance of black carbon (BC) and negligible brown carbon absorption, corroborated by very low organic carbon concentrations. India-wide EC emissions (12.5 Gg year⁻1) from residential kerosene lighting show a higher (∼50%) contribution from eastern India. Additionally, the use of oil lamps during the Diwali festival could emit ∼3 Gg of EC in two days, with a potential reduction of ∼90% if wax-based lamps replace oil lamps. These measured EFs, aerosol optical properties, and estimated emissions will help future studies derive more accurate climate and health impacts from these otherwise overlooked lighting devices.

Extreme wildfires over northern Greece during summer 2023 – Part A: Effects on aerosol optical properties and solar UV radiation

In Mediterranean countries, such as Greece, the frequency of forest fires has increased in recent years, primarily due to the widespread impacts of climate change. At the end of August 2023, Greece experienced a record-breaking heatwave that triggered severe wildfire incidents, significantly impacting the atmospheric conditions of several cities, among them Thessaloniki. A significant number of wildfires occurred in northern Greece (Evros), burning thousands of hectares of the protected Dadia forest (Natura 2000) and releasing a significant load of smoke into the atmosphere. According to the European Strategy Forum on Research Infrastructures (ESFRI) a total area of 90,000ha was burnt collectively by the Evros extreme wildfires during August 2023. The emissions led to severely adverse air pollution conditions, causing reduced visibility across an extended eastern Mediterranean region for several days. In this work, we analyze the influence of the transported biomass burning particles on the aerosol properties in the free troposphere, as well as on the surface UV radiation levels over Thessaloniki during the last week of August 2023. The transported smoke plume was detected over the Laboratory of Atmospheric Physics (LAP) in Thessaloniki, approximately 240 km away from the burning area, from August 22nd to the 25th. During this period, the presence of smoke led to exceptionally increased levels of aerosol optical depth (AOD), reaching up to 3.4 at 340nm (the highest ever recorded in Thessaloniki), as well as high Ångström exponent (AE) values, peaking at 2.4 for the 440–870nm range, followed by high Fine Mode Fractions (FMFs), indicating the prevalence of fine-mode smoke aerosol particle. Moreover, during the event, the presence of the biomass burning aerosols led to a strong attenuation of the solar UV irradiance by up to 90 %, reaching unprecedented levels, similar of a solar eclipse. The primary goal of this study is to highlight the extensive impacts that wildfires have, which are anticipated to increase in frequency in the near future, due to the predicted rise in the rate of occurrence of summer heatwaves especially for Mediterranean areas and specifically for Greece. Furthermore, the great value of the synergistic monitoring of the event with ground-based remote sensing instrumentation, along with satellite aerosol observations and modeling tools, is made prominent.

Bridging gas and aerosol properties between the northeastern US and Bermuda: analysis of eight transit flights

Abstract. The western North Atlantic Ocean is strongly influenced by continental outflow, making it an ideal region to study the atmospheric transition from a polluted coastline to the marine environment. Utilizing eight transit flights between the NASA Langley Research Center (LaRC) in Hampton, Virginia, and the remote island of Bermuda from NASA's Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE), we examine the evolution of trace gas and aerosol properties off the US East Coast. The first pair of flights flew along the wind trajectory of continental outflow, while the other flights captured a mix of marine and continental air mass sources. For measurements within the boundary layer (BL), there was an offshore decline in particle N<100 nm, N>100 nm, CH4, CO, and CO2 concentrations, all leveling off around ∼900 km offshore from the LaRC. These trends are strongest for the first pair of flights. In the BL, offshore declines in organic mass fraction and increases in sulfate mass fraction coincide with increasing hygroscopicity based on f(RH) measurements. Free troposphere measurements show a decline in N<100 nm, but other measured parameters are more variable when compared to the prominent offshore gradients seen in the BL. Pollution layers exist in the free troposphere, such as smoke plumes, that can potentially entrain into the BL. This work provides detailed case studies with a broad set of high-resolution measurements to further our understanding of the transition between continental and marine environments.

Data availability and requirements relevant for the Ariel space mission and other exoplanet atmosphere applications

Abstract The goal of this white paper is to provide a snapshot of the data availability and data needs primarily for the Ariel space mission, but also for related atmospheric studies of exoplanets and cool stars. It covers the following data-related topics: molecular and atomic line lists, line profiles, computed cross-sections and opacities, collision-induced absorption and other continuum data, optical properties of aerosols and surfaces, atmospheric chemistry, UV photodissociation and photoabsorption cross-sections, and standards in the description and format of such data. These data aspects are discussed by addressing the following questions for each topic, based on the experience of the “data-provider” and “data-user” communities: (1) what are the types and sources of currently available data, (2) what work is currently in progress, and (3) what are the current and anticipated data needs. We present a GitHub platform for Ariel-related data, with the goal to provide a go-to place for both data-users and data-providers, for the users to make requests for their data needs and for the data-providers to link to their available data. Our aim throughout the paper is to provide practical information on existing sources of data whether in databases, theoretical, or literature sources.

Recent improvements and maximum covariance analysis of aerosol and cloud properties in the EC-Earth3-AerChem model

Abstract. Given the importance of aerosols and clouds and their interactions in the climate system, it is imperative that the global Earth system models accurately represent processes associated with them. This is an important prerequisite if we are to narrow the uncertainties in future climate projections. In practice, this means that continuous model evaluations and improvements grounded in observations are necessary. Numerous studies in the past few decades have shown both the usability and the limitations of utilizing satellite-based observations in understanding and evaluating aerosol–cloud interactions, particularly under varying meteorological and satellite sensor sensitivity paradigms. Furthermore, the vast range of spatio-temporal scales at which aerosol and cloud processes occur adds another dimension to the challenges faced when evaluating climate models. In this context, the aim of this study is two-fold. (1) We evaluate the most recent, significant changes in the representation of aerosol and cloud processes implemented in the EC-Earth3-AerChem model in the framework of the EU project FORCeS compared with its previous CMIP6 version (Coupled Model Intercomparison Project Phase 6; https://pcmdi.llnl.gov/CMIP6/, last access: 13 February 2019). We focus particularly on evaluating cloud physical properties and radiative effects, wherever possible, using a satellite simulator. We report on the overall improvements in the EC-Earth3-AerChem model. In particular, the strong warm bias chronically seen over the Southern Ocean is reduced significantly. (2) A statistical, maximum covariance analysis is carried out between aerosol optical depth (AOD) and cloud droplet (CD) effective radius based on the recent EC-Earth3-AerChem/FORCeS simulation to understand to what extent the Twomey effect can manifest itself in the larger spatio-temporal scales. We focus on the three oceanic low-level cloud regimes that are important due to their strong net cooling effect and where pollution outflow from the nearby continent is simultaneously pervasive. We report that the statistical covariability between AOD and CD effective radius is indeed dominantly visible even at the climate scale when the aerosol amount and composition are favourably preconditioned to allow for aerosol–cloud interactions. Despite this strong covariability, our analysis shows a strong cooling/warming in shortwave cloud radiative effects at the top of the atmosphere in our study regions associated with an increase/decrease in CD effective radius. This cooling/warming can be attributed to the increase/decrease in low cloud fraction, in line with previous observational studies.

Influence of columnar versus vertical distribution of aerosol properties on the modulation of shortwave radiative effects

Quantifying the interaction of atmospheric aerosols with incoming solar radiation remains a challenge owing to the limitations associated with measuring aerosol optical properties. This study investigates how the distribution of aerosol properties, whether columnar or vertical, affects the aerosol radiative forcing (ARF) and heating rates (HRs) across different atmospheric layers under cloud-free conditions in the shortwave region. We also assess the atmospheric parameters, namely, pressure, temperature, water vapour density, and ozone density, from in-situ measurements, reanalysis data, and a standard tropical atmosphere to understand their impact on ARF and HR estimates across seasons. Our findings show that aerosol absorption is highest during monsoon, while it is lowest in the winter. Significant atmospheric warming due to aerosols resulted from the substantial cooling at the surface. Columnar properties of aerosols measured at limited or multiple wavelengths yield similar ARF and HR estimates, provided spectral dependency is considered using the Angstrom exponent across seasons. However, the vertical profiles of aerosol extinction, together with a constant single scattering albedo (SSA) along the atmospheric column versus an actual SSA profile, led to notable differences in ARF and HRs, specifically in pre-monsoon and monsoon periods. Free tropospheric aerosol absorption is underestimated when using columnar properties compared to vertical distribution, while boundary layer absorption is overestimated (> 10 Wm-2). The heterogeneity in aerosol types across atmospheric layers significantly influenced aerosol absorption, highlighting the importance of accurate vertical distribution information. HR profiles obtained with vertical distribution reflect the structure of aerosol extinction, whereas those estimated with columnar properties result in smoother profiles that fail to capture altitude gradients. Aerosol-induced HRs are higher within the boundary layer and free troposphere in the monsoon season for all scenarios of defined aerosol properties. These findings underscore the need for actual vertical profile measurements of aerosol properties to quantify aerosol radiation interaction.

Large-Scale Network-Based Observations of a Saharan Dust Event across the European Continent in Spring 2022

Between 14 March and 21 April 2022, an extensive investigation of an extraordinary Saharan dust intrusion over Europe was performed based on lidar measurements obtained by the European Aerosol Research Lidar Network (EARLINET). The dust episode was divided into two distinct periods, one in March and one in April, characterized by different dust transport paths. The dust aerosol layers were studied over 18 EARLINET stations, examining aerosol characteristics during March and April in four different regions (M-I, M-II, M-III, and M-IV and A-I, A-II, A-III, and A-IV, respectively), focusing on parameters such as aerosol layer thickness, center of mass (CoM), lidar ratio (LR), particle linear depolarization ratio (PLDR), and Ångström exponents (ÅE). In March, regions exhibited varying dust geometrical and optical properties, with mean CoM values ranging from approximately 3.5 to 4.8 km, and mean LR values typically between 36 and 54 sr. PLDR values indicated the presence of both pure and mixed dust aerosols, with values ranging from 0.20 to 0.32 at 355 nm and 0.24 to 0.31 at 532 nm. ÅE values suggested a range of particle sizes, with some regions showing a predominance of coarse particles. Aerosol Optical Depth (AOD) simulations from the NAAPS model indicated significant dust activity across Europe, with AOD values reaching up to 1.60. In April, dust aerosol layers were observed between 3.2 to 5.2 km. Mean LR values typically ranged from 35 to 51 sr at both 355 nm and 532 nm, while PLDR values confirmed the presence of dust aerosols, with mean values between 0.22 and 0.31 at 355 nm and 0.25 to 0.31 at 532 nm. The ÅE values suggested a mixture of particle sizes. The AOD values in April were generally lower, not exceeding 0.8, indicating a less intense dust presence compared to March. The findings highlight spatial and temporal variations in aerosol characteristics across the regions, during the distinctive periods. From 15 to 16 March 2022, Saharan dust significantly reduced UV-B radiation by approximately 14% over the ATZ station (Athens, GR). Backward air mass trajectories showed that the dust originated from the Western and Central Sahara when, during this specific case, the air mass trajectories passed over GRA (Granada, ES) and PAY (Payerne, CH) before reaching ATZ, maintaining high relative humidity and almost stable aerosol properties throughout its transport. Lidar data revealed elevated aerosol backscatter (baer) and PLDR values, combined with low LR and ÅE values, indicative of pure dust aerosols.