A dust plume rising to a maximum altitude of about 1 km above the springtime high-Arctic terrain of Lake Hazen, Nunavut, Canada was detected using a diverse array of passive and active, ...satellite-based remote sensing techniques. We were able to broadly characterize the 532 nm optical depth and particle size of the upper plume (0.5 ± 0.2 and 15–25 μm radius limits respectively). To our knowledge this is the first satellite-based remotely sensed, overland capture of what is an ubiquitous aeolian process across the Arctic: drainage winds inducing dust plumes that are funneled along basin pathways to spread over the water and land surfaces at the outlets of those pathways. The identification and characterization of the Lake Hazen plume was challenging given that there is little development of passive and active remote sensing techniques over Arctic terrains. Our findings suggest that Arctic-adapted remote sensing techniques that incorporate a priori information on dust optical properties can be exploited to identify and characterize locally generated plumes.
•A springtime, high-Arctic dust plume over Lake Hazen, Nunavut, Canada was detected using satellitebased remote sensing.•This is likely the first remotely sensed overland capture of a local dust plume over the Arctic.•Arctic-adapted RS techniques incorporating dust optical properties can be exploited to investigatelocally generated plumes.
The suggestion of Huang et al. (2015) on the climatological-scale transport
of Asian dust to the Arctic appears to be an important and worthwhile
assertion. It is unfortunate that the authors ...undermined, to a certain
degree, the quality of that assertion by a misinterpretation of the critical
24 March 2010 Arctic event (which was chosen by the authors to illustrate
their generalized, climatological-scale Arctic transport claim). They
attempted to characterize that key event using AERONET/AEROCAN retrievals
taken a day later and misinterpreted those largely cloud-dominated
retrievals as being representative of Asian dust while apparently not
recognizing that the coarse-mode aerosol optical depth retrievals on the previous day were actually coherent with their Arctic transport hypothesis.
In a companion paper (Xian et al., 2022, part 1 of the study), we present an Arctic aerosol optical depth (AOD) climatology and trend analysis for 2003-2019 spring and summertime periods derived from ...a combination of aerosol reanalyses, remote-sensing retrievals, and ground observations. Continued from the previous discussion and as the second part of the study, we report the statistics and trends of Arctic AOD extreme events using the U.S. Navy Aerosol Analysis and Prediction System ReAnalysis version 1 (NAAPS-RA v1), the sun photometer data from the AErosol RObotic NETwork (AERONET) sites, and the oceanic Maritime Aerosol Network (MAN) measurements. Here, extreme AOD events are defined as events with AOD exceeding the 95th percentile (denoted "AOD.sub.95 ") of AOD distributions for given locations using 6-hourly or daily AOD data. While AERONET and MAN data estimate the Arctic median 550 nm AOD value to be 0.07, the 95th percentile value is 0.24. Such extreme events are dominated by fine-mode aerosol particles, largely attributable to biomass burning (BB) smoke events for the North American Arctic, the Asian Arctic, and most areas of the Arctic Ocean. However, extreme AOD events for the lower European Arctic are more attributable to anthropogenic and biogenic fine particles. The extreme-event occurrence dominance of sea salt is largely limited to the North Atlantic and Norwegian Sea. The extreme AOD amplitudes of anthropogenic and biogenic fine-mode and sea salt AOD are, however, significantly lower than those regions where extreme smoke AOD is dominant. Even for sites distant from BB source regions, BB smoke is the principal driver of AOD variation above the AOD.sub.95 threshold.
We present an Arctic aerosol optical depth (AOD) climatology and trend analysis for 2003-2019 spring and summertime periods derived from a combination of multi-agency aerosol reanalyses, ...remote-sensing retrievals, and ground observations. This includes the U.S. Navy Aerosol Analysis and Prediction System ReAnalysis version 1 (NAAPS-RA v1), the NASA Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), and the Copernicus Atmosphere Monitoring Service ReAnalysis (CAMSRA). Spaceborne remote-sensing retrievals of AOD are considered from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Multi-angle Imaging SpectroRadiometer (MISR), and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Ground-based data include sun photometer data from AErosol RObotic NETwork (AERONET) sites and oceanic Maritime Aerosol Network (MAN) measurements. Aerosol reanalysis AODs and spaceborne retrievals show consistent climatological spatial patterns and trends for both spring and summer seasons over the lower Arctic (60-70.sup." N). Consistent AOD trends are also found for the high Arctic (north of 70.sup." N) from reanalyses. The aerosol reanalyses yield more consistent AOD results than climate models, can be verified well with AERONET, and corroborate complementary climatological and trend analysis. Speciated AODs are more variable than total AOD among the three reanalyses and a little more so for March-May (MAM) than for June-August (JJA). Black carbon (BC) AOD in the Arctic comes predominantly from biomass burning (BB) sources in both MAM and JJA, and BB overwhelms anthropogenic sources in JJA for the study period.
Extreme smoke event over the high Arctic Ranjbar, Keyvan; O'Neill, Norm T.; Lutsch, Erik ...
Atmospheric environment (1994),
12/2019, Letnik:
218
Journal Article
Recenzirano
The intense western Canadian fires of August 2017 resulted in a (10-year) extreme, high-Arctic smoke event. The primary measurements employed to monitor smoke events were fine mode (FM) aerosol ...optical depths (AODs) derived from the measured AOD spectra of two AEROCAN/AERONET (CIMEL) sunphotometers at Eureka, Nunavut, Canada. The FM AOD attribution is argued to be a necessary condition for the presence of smoke. Various supporting information, including the correlation with smoke proxy (CO) retrievals, the high frequency (rapid diurnal variation) and the high amplitude nature of the FM AODs, ground-based backscatter lidar profiles, the redundancy of the double CIMEL retrievals, satellite remote sensing, aerosol modeling and backtrajectories indicated that the peak event was likely due to smoke from extreme pyroCb fires in British Columbia.
The hypothesis that the FM AOD peak event was an extreme event was tested for a derived ensemble of fine mode events and their peaks over the 10-year sampling period. The results confirmed the hypothesis at the 0.001 level of significance. Important indicators that the 10-year ensemble of FM AOD events did indeed represent smoke were their high frequency and high amplitude FM nature, their occurrence during the Boreal forest fire and agricultural fire seasons in Canada and Asia, and their strong correlation with CO abundances retrieved from FTIR measurements (when sufficient FM AOD and CO statistics were available).
In the process of accumulating climatological-scale, monthly-binned fine mode AOD statistics, we found moderate correlations with forest fire or agricultural fire emissions from the Boreal North American, Boreal Asia or Central Asia regions as well as with CO retrievals at Eureka. We argued that confounding factors constraining the monthly binned fine mode AOD vs emissions correlations were associated with the monthly-binned meteorological dynamics (with notable, event-level, exceptions) while confounding factors constraining fine mode AOD vs CO correlations included the different physio-optical nature of those smoke proxies (solar attenuation by fine mode particle scattering versus solar attenuation by molecular absorption). We also employed historic (2005-2010) AHSRL (Arctic High Spectral Resolution Lidar) profiles to estimate an optically averaged smoke plume height of ~3 to 3 ½ km during the spring and summer seasons.
The sub-micron (SM) aerosol optical depth (AOD) is an optical separation based on the fraction of particles below a specified cutoff radius of the particle size distribution (PSD) at a given particle ...radius. It is fundamentally different from spectrally separated FM (fine-mode) AOD. We present a simple (AOD-normalized) SM fraction versus FM fraction (SMF vs. FMF) linear equation that explains the well-recognized empirical result of SMF generally being greater than the FMF. The AERONET inversion (AERinv) products (combined inputs of spectral AOD and sky radiance) and the spectral deconvolution algorithm (SDA) products (input of AOD spectra) enable, respectively, an empirical SMF vs. FMF comparison at similar (columnar) remote sensing scales across a variety of aerosol types.
The sub-micron (SM) aerosol optical depth (AOD) is an
optical separation based on the fraction of particles below a specified cutoff radius of the particle size distribution (PSD) at a given particle
...radius. It is fundamentally different from spectrally separated FM (fine-mode) AOD. We present a simple (AOD-normalized) SM fraction versus FM
fraction (SMF vs. FMF) linear equation that explains the well-recognized
empirical result of SMF generally being greater than the FMF. The AERONET
inversion (AERinv) products (combined inputs of spectral AOD and sky
radiance) and the spectral deconvolution algorithm (SDA) products (input of
AOD spectra) enable, respectively, an empirical SMF vs. FMF comparison at
similar (columnar) remote sensing scales across a variety of aerosol types. SMF (AERinv-derived) vs. FMF (SDA-derived) behavior is primarily dependent on the relative truncated portion (εc) of the coarse-mode (CM) AOD associated with the cutoff portion of the CM PSD and, to a second order, the cutoff FM PSD and FM AOD (εf). The SMF vs. FMF equation largely explains the SMF vs. FMF behavior of the AERinv vs. SDA products as a
function of PSD cutoff radius (“inflection point”) across an ensemble of
AERONET sites and aerosol types (urban-industrial, biomass burning, dust,
maritime and a mixed class of Arctic aerosols). The overarching dynamic was
that the linear SMF vs. FMF relation pivots clockwise about the
approximate (SMF, FMF) singularity of (1, 1) in a “linearly inverse”
fashion (slope and intercept of approximately 1−εc and εc) with increasing cutoff radius. SMF vs. FMF slopes and intercepts derived from AERinv and SDA retrievals confirmed the general domination of εc over εf in controlling
that dynamic. A more general conclusion is the apparent confirmation that
the optical impact of truncating modal (whole) PSD features can be detected
by an SMF vs. FMF analysis.
In this work we report the airborne aerosol optical depth (AOD) from measurements within freshly emitted anthropogenic plumes arising from mining and processing operations in the Athabasca Oil Sands ...Region (AOSR) in the context of ground-based AERONET climatological daily averaged AODs at Fort McMurray (Alberta, Canada). During two flights on 9 and 18 June 2018, the NASA airborne 4STAR (Spectrometers for Sky-Scanning, Sun-Tracking Atmospheric Research) Sun photometer registered high fine-mode (FM, <1 µm) in-plume AODs of up to 0.4 and 0.9, respectively, in the vicinity of the plume source (<20 km). Particle composition shows that the plumes were associated with elevated concentrations of sulfates and ammonium. These high AODs significantly exceed climatological averages for June and were not captured by the nearby AERONET instrument (mean daily AODs of 0.10±0.01 and 0.07±0.02, maximum AOD of 0.12) due possibly to horizontal inhomogeneity of the plumes, plume dilution and winds which in certain cases were carrying the plume away from the ground-based instrument. The average 4STAR out-of-plume (background) AODs deviated only marginally from AERONET daily averaged values. While 4STAR AOD peaks were generally well correlated in time with peaks in the in situ-measured particle concentrations, we show that differences in particle size are the dominant factor in determining the 4STAR-derived AOD. During the two flights of 24 June and 5 July 2018 when plumes likely travelled distances of 60 km or more, the average 4STAR FM AOD increased by 0.01–0.02 over ∼50 km of downwind particle evolution, which was supported by the increases in layer AODs calculated from the in situ extinction measurements. Based on these observations as well as the increases in organic mass, we attribute the observed AOD increase, at least in part, to secondary organic aerosol formation. The in-plume and out-of-plume AODs for this second pair of flights, in contrast to clear differences in in situ optical and other measurements, were practically indistinguishable and compared favourably to AERONET within 0.01–0.02 AOD. This means that AERONET was generally successful in capturing the background AODs, but missed some of the spatially constrained high-AOD plumes with sources as close as 30–50 km, which is important to note since the AERONET measurements are generally thought to be representative of the regional AOD loading. The fact that industrial plumes can be associated with significantly higher AODs in the vicinity of the emission sources than previously reported from AERONET can potentially have an effect on estimating the AOSR radiative impact.
Abstract Convective clouds play an important role in the Earth’s climate system and are a known source of extreme weather. Gaps in our understanding of convective vertical motions, microphysics, and ...precipitation across a full range of aerosol and meteorological regimes continue to limit our ability to predict the occurrence and intensity of these cloud systems. Towards improving predictability, the National Science Foundation (NSF) sponsored a large field experiment entitled “Experiment of Sea Breeze Convection, Aerosols, Precipitation, and Environment (ESCAPE).” ESCAPE took place between 30 May - 30 Sept. 2022 in the vicinity of Houston, TX because this area frequently experiences isolated deep convection that interacts with the region's mesoscale circulations and its range of aerosol conditions. ESCAPE focused on collecting observations of isolated deep convection through innovative sampling, and on developing novel analysis techniques. This included the deployment of two research aircraft, the National Research Council of Canada Convair-580 and the Stratton Park Engineering Company Learjet, which combined conducted 24 research flights from 30 May to 17 June. On the ground, three mobile X-band radars, and one mobile Doppler lidar truck equipped with soundings, were deployed from 30 May to 28 June. From 1 August to 30 Sept. 2022, a dual-polarization C-band radar was deployed and operated using a novel, multi-sensor agile adaptive sampling strategy to track the entire lifecycle of isolated convective clouds. Analysis of the ESCAPE observations has already yielded preliminary findings on how aerosols and environmental conditions impact the convective life cycle.
Behavioral Diseases Counseling Centers (BDCCs) and Vulnerable Women's Counseling Centers (VWCCs) in Iran are the main peripheral centers that offer educational, counseling, diagnostic, preventive, ...curative and protective services to individuals living with or at high risk of contracting HIV/AIDS and female sex workers respectively. Due to the social stigma surrounding HIV in Iran, this study aims to identify the factors that may hinder or encourage HIV/AIDS patients and women with risky sexual behaviors from visiting these centers.
Conducted in 2023, this qualitative study involved individuals visiting BDCCs and VWCCs in two western provinces of Iran, Ilam and Kermanshah. The study participants included 21 health staff members working in BDCCs and VWCCs and 20 HIV/AIDS patients and vulnerable women with unsafe sexual behaviors referring to these centers. Purposive, snowball and maximum variation sampling techniques were applied to interview the participants. Interviews were conducted between January 5th and May 21st, 2023, using a semi-structure guideline. Interviews were transcribed and content analysis approach was applied to analyze data using MAXQDA20 software.
According to the findings, the barriers and facilitators of visiting specialized centers for HIV/AIDS patients and vulnerable women were categorized into three main categories, 10 subcategories and 35 sub-subcategories including: Medical and operational processes (4 subcategories and 12 sub-subcategories), mutual interactions between the personnel and visitors (people living with and at the risk of getting HIV/AIDS) (3 subcategory and 13 sub-subcategories), and physical characteristics of the centers (3 subcategories and 10 sub-subcategories).
To improve the performance of BDCCs and VWCCs and encourage people living with and at the risk of contracting HIV/AIDS to visit these centers regularly, health policy makers should consider modifying clinical processes, physical features, personnel behaviors and visitors' concerns raised by the interviewees and the issues identified in this study.
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