Spatial Distribution Of Aerosols Research Articles

Size-resolved spatial distribution analysis of aerosols with or without the utilization of a novel aerosol containment device in dental settings.

The coronavirus disease 2019 pandemic has imposed unprecedented occupational challenges for healthcare professionals. In dentistry, handheld instruments such as air and electric handpieces, ultrasonic scalers, and air/water syringes are capable of generating aerosols, droplets, and splatter, thereby exposing dental professionals to airborne contaminants such as viruses, bacteria, and fungi. The objective of the present study was to determine the spatial distribution of aerosols by size (0.30 to 20.00 μm) and the efficacy of a novel aerosol containment device (ACD) in a large operatory room with 12 dental chairs. Real-time portable laser aerosol spectrometers were used to measure the size-resolved number concentration of aerosols generated by a collision nebulizer. Results reported demonstrate that aerosol number concentrations significantly decreased as a function of distance with or without the utilization of the ACD. The ACD was able to efficiently decrease (up to 8.56-fold) the number and size distribution of particles in a large dental clinic. The novel device demonstrated higher efficiency for particles shown to contain the highest levels of severe acute respiratory syndrome coronavirus 2 in Chinese hospitals, thereby showing great promise to potentially decrease the spreading of nosocomial pathogens in dental settings.

Assessing the spatial distribution of aerosols and air quality over the Ganga River basin during COVID-19 lockdown phase-1

The present study aims to analyze the variations in aerosol optical depth (AOD), black carbon (BC), organic carbon (OC), sulfate (SO4), dust, sea salt, fine mode dust and sea salt, and air quality over the Ganga River basin (GB), during the nation-wise lockdown phase-1 due to the outbreak of COVID-19. The aerosol data have been obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) and Modern-Era Retrospective analysis for Research and Applications (MERRA-2) for the lockdown phase-1 (March 25 - April 15, 2020) and its corresponding average of the reference period (2001-2019). The total PM2.5 has been modeled over the GB based on the inputs from MERRA-2. The in-situ air quality index (AQI) values from cities across the GB have been obtained during pre-lockdown (February, 29 - March 20, 2020) and lockdown phase-1 period to evaluate changes. Non-parametric pairwise comparison is performed to evaluate the significant change in the pollutants including AOD, and quantile regression is used to explore the effect of meteorology on AOD and other pollutants. The results show a significant reduction (p ≤ 0.05) in AOD, BC, OC, SO4, dust, dust particulate matter (PM2.5), sea salt, sea salt PM2.5, and estimated total PM2.5 during the lockdown phase-1 with respect to the reference period. The analysis also reveals that meteorological factors do not play a vital role in the reduction of AOD during the lockdown phase-1 period. The estimated reductions for AOD, BC, OC, SO4, dust, dust PM2.5, sea salt, and sea salt PM2.5 are 33%, 21%, 24%, 20%, 18%, 17%, 64%, and 61%, respectively due to imposition of lockdown measures. As many as 28 cities in the GB have shown substantial improvement in the air quality during the lockdown phase-1 period. The reduction in the emission quantity and subsequent improvement in AQI has opened up a new discourse for combatting the persistent air quality issues for million-plus cities in particular and for the north Indian plain in general. The findings of this study thus provide insightful views to the environmentalists and policymakers for framing better emission policy to deal with the air quality issue.

The spatial distribution of aerosols in high-speed bone burring with external irrigation

It is well-known that the use of high-speed burring devices with irrigation used in bone surgery produces aerosols, and can toss tissue particles into space. The aim of this study was to assess the spatial vertical contamination in the sterile operation field while using a high-speed cutting device at various locations.A fresh porcine knee was resected for 10 min with a high-speed burring device. To determine the spatial contamination distribution bacteria were used as a tracer. In this novel method for detecting environmental contamination droplets of the contaminated irrigation solution were collected on vertically mounted Petri dishes and the number of colony-forming units was counted.Contamination of varying intensity was observed throughout the room. The highest contamination was found perpendicular to the bur rotation axis in a distance 0.5 m from the bur, at a height of 1.4 m. Around this spot, colony-forming units count isotropically drops to less than 100 CFUs at an area of 0.5 m in diameter.The contamination decreases with increasing distance to the bur head and a main direction of contamination was identified. Placing critical sterile objects in the highly contaminated space during and after bone resection procedures should be avoided whenever possible.

Composite Aerosol Optical Depth Mapping over Northeast Asia from GEO-LEO Satellite Observations

This study aimed to generate a near real time composite of aerosol optical depth (AOD) to improve predictive model ability and provide current conditions of aerosol spatial distribution and transportation across Northeast Asia. AOD, a proxy for aerosol loading, is estimated remotely by various spaceborne imaging sensors capturing visible and infrared spectra. Nevertheless, differences in satellite-based retrieval algorithms, spatiotemporal resolution, sampling, radiometric calibration, and cloud-screening procedures create significant variability among AOD products. Satellite products, however, can be complementary in terms of their accuracy and spatiotemporal comprehensiveness. Thus, composite AOD products were derived for Northeast Asia based on data from four sensors: Advanced Himawari Imager (AHI), Geostationary Ocean Color Imager (GOCI), Moderate Infrared Spectroradiometer (MODIS), and Visible Infrared Imaging Radiometer Suite (VIIRS). Cumulative distribution functions were employed to estimate error statistics using measurements from the Aerosol Robotic Network (AERONET). In order to apply the AERONET point-specific error, coefficients of each satellite were calculated using inverse distance weighting. Finally, the root mean square error (RMSE) for each satellite AOD product was calculated based on the inverse composite weighting (ICW). Hourly AOD composites were generated (00:00–09:00 UTC, 2017) using the regression equation derived from the comparison of the composite AOD error statistics to AERONET measurements, and the results showed that the correlation coefficient and RMSE values of composite were close to those of the low earth orbit satellite products (MODIS and VIIRS). The methodology and the resulting dataset derived here are relevant for the demonstrated successful merging of multi-sensor retrievals to produce long-term satellite-based climate data records.

Aerosol-UA satellite mission for the polarimetric study of aerosols in the atmosphere

We discuss the current state of the Ukrainian space project Aerosol-UA, which aims to provide data on the aerosol spatial distribution and microphysics in the Earth's atmosphere. The Aerosol-UA remote sensing concept is based on measurements from the multispectral Scanning Polarimeter (ScanPol) and the MultiSpectral Imaging Polarimeter (MSIP) on board the Yuzhnoe satellite (YuzhSat) platform. The ScanPol instrument is intended to measure intensity and polarization state of the light scattered by the Earth surface and atmosphere in the six spectral bands in the range from 370 to 1620 nm. The MSIP consists of five optical units and is intended to measure intensity and polarization state of the scattered light in the eight spectral bands in the range from 410 to 910 nm. The MSIP includes three polarimetric units (three spectral bands) and two radiometric units (eight spectral bands). These two Aerosol-UA instruments combined provide multi-angular measurements of the Stokes parameters of scattered radiance from the same scene. With the onboard calibration devices, the ScanPol allows the instruments to cross-calibrate as the fields-of-view of the two instruments are partly overlapped. We developed a polarimetric model for the instrument's pre-flight calibration and calibration procedure, based on that model. The model demonstrated good validity with the MSIP 555P nm polarimetric unit calibration experiment, and the errors of degree and azimuth of the linear light polarization were estimated at ~0.6% and ~0.2°, respectively. We considered details of the ScanPol pre-flight and in-flight radiometric and polarimetric calibration. The in-flight calibration set is used to perform polarized radiation calibration, depolarized radiation calibration, black body calibration, and radiometric calibration of the ScanPol. We discuss the ScanPol in-flight calibration with the solar diffuser plate, including the Spectralon flat diffuser plate and alternative possibilities. Vicarious methods, such as Rayleigh scattering, test sites, and Moon observations were considered for MSIP calibration. The data processing approach is also described in this paper.

Vertical and spatial distribution of elevated aerosol layers obtained using long-term ground-based and space-borne lidar observations

In this study, long-term ground-based and space-borne lidar measurements are used to understand the vertical (surface to 30 km) and spatial distribution of aerosols. First, the vertical distribution of aerosol extinction (AE) covering from near surface to 30 km is provided by combining Micro Pulse Lidar and Mie lidar observations co-located over a tropical station Gadanki (13.5oN, 79.2oE), India. The presence of two elevated aerosol layers, one between 2 and 5 km (lower troposphere) and the other between 15 and 18 km (Upper Troposphere and Lower Stratosphere (UTLS)), are simultaneously observed during the Indian summer monsoon season. Second, the spatial extent of these elevated aerosol layers obtained using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements reveals the presence of the lower layer extending from Africa to South Asia during both pre–monsoon and monsoon seasons. However, the UTLS layer is confined from middle-east to the China Sea only during monsoon season, also known as Asian Tropopause Aerosol Layer (ATAL). Third, aerosol sub-types obtained for these elevated aerosol layers using CALIPSO measurements reveals the dominance of polluted dust (44.6%) whereas the occurrence frequency of polluted continental, dust and elevated smoke is ~19.6%, 20.7% and 13.1%, respectively, for the lower layer. However, the frequency of volcanic ash and sulfate aerosols is ~50.3% and 49.7%, respectively, for the UTLS layer. Depolarization ratio (color ratio) values varies between 0.21 and 0.34 (>0.6) in the lower layer while the values >0.15 (<0.6) are present in the UTLS layer during monsoon season revealing the influence of non-spherical and coarse mode particles in the lower layer while spherical and fine mode particles in the UTLS region over the site. This information is very much useful in estimating reliable radiative forcing due to these elevated aerosol layers on the background atmosphere involved in assessing their impact on the regional climate.

Spatial Distribution of Atmospheric Aerosol Physicochemical Characteristics in the Russian Sector of the Arctic Ocean

The results from studies of aerosol in the Arctic atmosphere are presented: the aerosol optical depth (AOD), the concentrations of aerosol and black carbon, as well as the chemical composition of the aerosol. The average aerosol characteristics, measured during nine expeditions (2007–2018) in the Eurasian sector of the Arctic Ocean, had been 0.068 for AOD (0.5 µm); 2.95 cm−3 for particle number concentrations; 32.1 ng/m3 for black carbon mass concentrations. Approximately two–fold decrease of the average characteristics in the eastern direction (from the Barents Sea to Chukchi Sea) is revealed in aerosol spatial distribution. The average aerosol characteristics over the Barents Sea decrease in the northern direction: black carbon concentrations by a factor of 1.5; particle concentrations by a factor of 3.7. These features of the spatial distribution are caused mainly by changes in the content of fine aerosol, namely: by outflows of smokes from forest fires and anthropogenic aerosol. We considered separately the measurements of aerosol characteristics during two expeditions in 2019: in the north of the Barents Sea (April) and along the Northern Sea Route (July–September). In the second expedition the average aerosol characteristics turned out to be larger than multiyear values: AOD reached 0.36, particle concentration up to 8.6 cm−3, and black carbon concentration up to 179 ng/m3. The increased aerosol content was affected by frequent outflows of smoke from forest fires. The main (99%) contribution to the elemental composition of aerosol in the study regions was due to Ca, K, Fe, Zn, Br, Ni, Cu, Mn, and Sr. The spatial distribution of the chemical composition of aerosols was analogous to that of microphysical characteristics. The lowest concentrations of organic and elemental carbon (OC, EC) and of most elements are observed in April in the north of the Barents Sea, and the maximal concentrations in Far East seas and in the south of the Barents Sea. The average contents of carbon in aerosol over seas of the Asian sector of the Arctic Ocean are OC = 629 ng/m3, EC = 47 ng/m3.

Mobile Aerosol Raman Polarizing Lidar LOSA-A2 for Atmospheric Sounding

The mobile aerosol Raman polarizing lidar LOSA-A2 designed at V.E. Zuev Institute of Atmospheric Optics SB RAS is presented. Its main technical specifications are given. The lidar carries out sounding of the atmosphere of a Nd:YAG laser at two wavelengths, 1064 nm and 532 nm. Optical selection of lidar signals at these wavelengths is performed by two identical telescopes with diameters of 120 mm and a focal length of 500 mm. In the visible channel, the signal is divided into two orthogonal polarized components, and a Raman signal at a wavelength of 607 nm is separated. The lidar was tested in aircraft and ship research expeditions. Results of the study of spatial aerosol distribution over the Baikal with the use of LOSA-A2 lidar received during ship-based research expeditions are described. The first in situ tests of the lidar were carried out in an aircraft expedition in the north of Western Siberia.

Comparison of MODIS- and CALIPSO-Derived Temporal Aerosol Optical Depth over Yellow River Basin (China) from 2007 to 2015

In this study, Collection 6.1 (C6.1) of different aerosol optical depth (AOD) products of different spatial resolutions were used from the aqua moderate resolution imaging spectroradiometer (MODIS) including dark target (DT), deep blue (DB), deep blue (DB), and DT-DB (DTB). These products were compared with cloud-aerosol lidar, and infrared pathfinder satellite observation (CALIPSO) AOD retrievals over the Yellow River Basin (YERB), China from 2003 to 2017. The YERB was divided into three sub-regions, namely YERB1 (the mountainous terrain in the upper reaches of the YERB), YERB2 (the Loess Plateau region in the middle reaches of the YERB), and YERB3 (the plain region downstream of the YERB). Errors and agreement between MODIS and CALIPSO data were reported using Pearson’s correlation (R) and relative mean bias (RMB). Results showed that the CALIPSO whole layers AOD (AODS) were better matched with MODIS AOD than the CALIPSO lowest layer AOD (AOD1). The time series of AOD shows higher values in spring and summer, and a small difference in AOD products was observed in autumn. The overall average value of CALIPSO AOD and MODIS AOD both fitted the order: YERB3 > YERB2 > YERB1. The CALIPSO AOD retrievals have the best consistency with the DTB10K and the lowest consistency with DT3K. Overall, the regional distributions of the CALIPSO AOD and MODIS AOD are significantly different over the YERB, and the difference is closely related to the season, region, and topography. This study can help researchers understand the difference of aerosol temporal and spatial distribution utilizing different satellite products over YERB, and also can provide data and technical support for the government in atmospheric environmental governance over YERB.

Spatial Distribution and Impacts of Aerosols on Clouds Under Meiyu Frontal Weather Background Over Central China Based on Aircraft Observations

AbstractAn airborne field campaign was conducted from 10 June to 10 July 2018 in Hubei Province over central China as a part of the State Key Natural Science Foundation Project referred to as Integrative Monsoon Frontal Rainfall Experiment (IMFRE). Comprehensive observations of atmospheric aerosols and cloud characteristics in this region were collected and analyzed. In this study, data from six flights on nonprecipitating days were selected to investigate the spatial distribution of aerosols and microphysical properties of clouds. The profiles of aerosol number concentrations (Na) were 1 order of magnitude lower than those over the North Plain of China, due to the different atmospheric backgrounds, local emission, and long‐range transport. The highest Na occurred at the altitude of the temperature inversion layer (TIL), indicating that Na profiles were significantly affected by the TIL structure. Relative humidity (RH) had an effect on the aerosol size distribution where high RH values corresponded well with large values of particle mean diameter (MD). Compared with the vertical distributions of Na and MD, their horizontal directions had minor changes, except for the MD at 4,000 m in one case. Of the three flights that penetrated through the stratiform clouds, the probability distribution functions of cloud droplet number concentration (Nc), effective radius (re), and liquid water content (LWC), showed the same features with a single peak mode. Since the nucleation of aerosol in‐cloud caused the decrease of aerosol concentration, the maximum aerosol activation ratio almost reached 74%. The average spectrum of cloud droplets showed a multimodal distribution and their microphysical properties were analyzed in this study.

The Urban–Rural Heterogeneity of Air Pollution in 35 Metropolitan Regions across China

Urbanization and air pollution are major anthropogenic impacts on Earth’s environment, weather, and climate. Each has been studied extensively, but their interactions have not. Urbanization leads to a dramatic variation in the spatial distribution of air pollution (fine particles) by altering surface properties and boundary-layer micrometeorology, but it remains unclear, especially between the centers and suburbs of metropolitan regions. Here, we investigated the spatial variation, or inhomogeneity, of air quality in urban and rural areas of 35 major metropolitan regions across China using four different long-term observational datasets from both ground-based and space-borne observations during the period 2001–2015. In general, air pollution in summer in urban areas is more serious than in rural areas. However, it is more homogeneously polluted, and also more severely polluted in winter than that in summer. Four factors are found to play roles in the spatial inhomogeneity of air pollution between urban and rural areas and their seasonal differences: (1) the urban–rural difference in emissions in summer is slightly larger than in winter; (2) urban structures have a more obvious association with the spatial distribution of aerosols in summer; (3) the wind speed, topography, and different reductions in the planetary boundary layer height from clean to polluted conditions have different effects on the density of pollutants in different seasons; and (4) relative humidity can play an important role in affecting the spatial inhomogeneity of air pollution despite the large uncertainties.

Dental aerosols: microbial composition and spatial distribution

ABSTRACT Background: High-speed dental instruments produce aerosols, which can contribute to the transmission of pathogenic microorganisms. The aim of this study is to describe the microbial load and – composition and spatial distribution of aerosols in dental clinics. Methods: In four dental clinics active and passive sampling methods were used before, during and after treatment and at different locations. Retrieved colony forming units (CFU) were sequenced for taxon identification. Results: The samples contained up to 655 CFU/plate/30 minutes and 418 CFU/m3/30 minutes during dental treatment for active and passive sampling, respectively. The level of contamination after treatment and at 1.5 m distance from the patient’s head was similar to the start of the day. The highest contamination was found at the patient’s chest area. The aerosols consisted of 52 different taxa from human origin and 36 from water. Conclusion: Contamination in dental clinics due to aerosols is mainly low, although high level of contamination with taxa from both human and water origin was found within 80 cm around the head of the patient. Our results stress the importance of infection control measures on surfaces in close proximity to the head of the patient as well as in dental water lines.

Observations of Aerosol Spatial Distribution and Emissions in New York City Using a Scanning Micro Pulse Lidar

In order to better understand the behavior of particulate pollution and atmospheric dynamics in New York City, it is of great importance to analyze the spatial distribution of aerosols. A scanning lidar system allows for horizontal range-resolved observations of aerosol backscatter with high space and time resolution. A challenge to analyzing the lidar returns is to disentangle extinction over the range of the observations to retrieve the backscatter coefficient with distance. This work presents horizontal measurements taken with a scanning eye-safe Micro Pulse Lidar in New York City. The measurements are analyzed using the Slope Method to get an estimate of the range-resolved aerosol backscatter coefficient. The results are presented as backscatter coefficient maps that display the aerosol spatial distribution within the field of view of the scanning pattern deployed. These observations clearly resolve aerosol dynamics and emission sources within the urban areas.

Characteristics of Aerosols over the Summer Monsoon Transition Zone

A survey was conducted in the summer monsoon transition region of China. By combining data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSOs) and Moderate Resolution Imaging Spectroradiometer (MODIS), the effects of East Asian summer monsoon circulation on the spatial distribution of aerosol, as well as the response mechanisms of different aerosols in an abundant and a deficient summer monsoon year, were analyzed. It was found that, in the summer monsoon transition region, the aerosol optical depth (AOD) in abundant monsoon years was lower than that in deficient years. Only in the Gobi Desert region of the Loess Plateau, the AOD in abundant monsoon years was significantly larger than that in deficient years. When the AOD was less than 0.06, the frequency of dust aerosol was higher than that of polluted aerosol in both the abundant and deficient monsoon years. When the AOD was over 0.06, the frequency of polluted aerosol was higher than that of dust aerosol in both the abundant and deficient monsoon years. In summer, the AOD was larger and the frequency of polluted aerosol in abundant monsoon years was higher than that in deficient years.

AN AEROSOL LIDAR DATA VISUALIZATION METHOD BASED ON ARCGIS

Abstract. The geographical information, temporal and spatial distribution of pollution sources cannot be accurately described by the traditional aerosol lidar inversion data. In order to accurately locate the pollution sources and monitor the spatial and temporal distribution of pollutants, an aerosol lidar data visualization method based on ArcGIS is proposed in this paper. A natural neighborhood method is used to perform group interpolation on ArcGIS software, and the range range-extinction coefficient relationship diagram is plotted using the aerosol optical data obtained from Klett inversion algorithm. The geographic information is added to the lidar inversion data in this diagram. The aerosol spatial and temporal distribution range and the direction of aerosol diffusion are accurately displayed directly. The change of aerosol concentration is plotted in different colors, the visually displaying the concentration of pollutants in the detection area is realized. The aerosol detection data in the sunny and haze days in Yinchuan are visualized in this paper. The result shows that this method can quickly determine the geographical location of pollution sources and visualize the spatial and temporal distribution of aerosols. This method can be used to display aerosol data with geographic information for meteorological and environmental protection departments. This method can provide data support for meteorological and environmental protection departments to quickly determine the location and concentration of pollution sources.

Investigations into the development of a satellite-based aerosol climate data record using ATSR-2, AATSR and AVHRR data over north-eastern China from 1987 to 2012

Abstract. Satellites provide information on the temporal and spatial distributions of aerosols on regional and global scales. With the same method applied to a single sensor all over the world, a consistent data set is to be expected. However, the application of different retrieval algorithms to the same sensor and the use of a series of different sensors may lead to substantial differences, and no single sensor or algorithm is better than any other everywhere and at all times. For the production of long-term climate data records, the use of multiple sensors cannot be avoided. The Along Track Scanning Radiometer (ATSR-2) and the Advanced ATSR (AATSR) aerosol optical depth (AOD) data sets have been used to provide a global AOD data record over land and ocean of 17 years (1995–2012), which is planned to be extended with AOD retrieved from a similar sensor. To investigate the possibility of extending the ATSR data record to earlier years, the use of an AOD data set from the Advanced Very High Resolution Radiometer (AVHRR) is investigated. AOD data sets used in this study were retrieved from the ATSR sensors using the ATSR Dual View algorithm ADV version 2.31, developed by Finnish Meteorological Institute (FMI), and from the AVHRR sensors using the aerosol optical depth over land (ADL) algorithm developed by RADI/CAS. Together, these data sets cover a multi-decadal period (1987–2012). The study area includes two contrasting areas, both in regards to aerosol content and composition and surface properties, i.e. a region over north-eastern China, encompassing a highly populated urban/industrialized area (Beijing–Tianjin–Hebei) and a sparsely populated mountainous area. Ground-based AOD observations available from ground-based sun photometer AOD data in AERONET and CARSNET are used as a reference, together with broadband extinction method (BEM) data at Beijing to cover the time before sun photometer observations became available in the early 2000s. In addition, MODIS-Terra C6.1 AOD data are used as a reference data set over the wide area where no ground-based data are available. All satellite data over the study area were validated against the reference data, showing the qualification of MODIS for comparison with ATSR and AVHRR. The comparison with MODIS shows that AVHRR performs better than ATSR in the north of the study area (40∘ N), whereas further south ATSR provides better results. The validation against sun photometer AOD shows that both AVHRR and ATSR underestimate the AOD, with ATSR failing to provide reliable results in the wintertime. This is likely due to the highly reflecting surface in the dry season, when AVHRR-retrieved AOD traces both MODIS and reference AOD data well. However, AVHRR does not provide AOD larger than about 0.6 and hence is not reliable when high AOD values have been observed over the last decade. In these cases, ATSR performs much better for AOD up to about 1.3. AVHRR-retrieved AOD compares favourably with BEM AOD, except for AOD higher than about 0.6. These comparisons lead to the conclusion that AVHRR and ATSR AOD data records each have their strengths and weaknesses that need to be accounted for when combining them in a single multi-decadal climate data record.

High rate diffusion-scale approximation for counters with extendable dead time

Abstract Measuring occurrence times of random events, aimed to determine the statistical properties of the governing stochastic process, is a basic topic in science and engineering, and has been the subject of numerous mathematical modeling approaches. Often, true statistical properties deviate from measured properties due to the so called dead time phenomenon, where for a certain time period following detection, the detection system is not operational. Understanding the dead time effect is especially important in radiation measurements, often characterized by high count rates and a non-reducible detector dead time (originating in the physics of particle detection). The effect of dead time can be interpreted as a suitable rarefied sequence of the original time sequence. This paper provides a limit theorem for a high rate (diffusion-scale) counter with extendable (Type II) dead time, where the underlying counting process is a renewal process with finite second moment for the inter-event distribution. The results are very general, in the sense that they refer to a general inter arrival time and a random dead time with general distribution. Following the theoretical results, we will demonstrate the applicability of the results in three applications: serially connected components, multiplicity counting and measurements of aerosol spatial distribution.

Assessment of air pollution in Krasnoyarsk based on satellite data of different spatial resolution

Spectrometer MODIS, installed on TERRA and AQUA satellites, provides daily global coverage of the Earth. Based on its measurements, data on aerosol optical depth (AOD) with different spatial resolution are formed: 10, 3, 1 km. The classical algorithm with a coarse spatial resolution of 10 km is not suitable for studying the variability of aerosols at the city scale. Introduced in 2018, a new algorithm for multi-angle implementation of atmospheric correction (MAIAC) provides AOD data with spatial resolution of 1 km. This information can already be used to analyze the spatial distribution of aerosols in the city. The relationship between MAIAC AOD and PM2.5 concentrations of particulate matter was investigated, which is measured at automated posts of city environmental services. Our analysis showed that the data with a spatial resolution of 1 km allow us to see the areas of dust pollution inside the city. This information, together with measurements at the posts, can be used as an objective assessment of the environmental situation.

2006~2016年四川盆地气溶胶光学厚度时空变化特征及其气象影响因素分析

2006~2016年四川盆地气溶胶光学厚度时空变化特征及其气象影响因素分析

Climatological Analysis of Aerosols Optical Properties by Airborne Sensors and in Situ Measurements in West Africa: Case of the Sahelian Zone

This paper deals with the climatology of aerosols in West Africa based on satellite and in situ measurements between 2001 and 2016 and covers four sites in the Sahelian zone. There are indeed Banizoumbou (13.541°N, 02.665°E), Cinzana (13.278°N, 05.934°W), Dakar (14.394°N, 16.959°W) and Ouagadougou (12.20°N, 1.40°W) located respectively in Niger, Mali, Senegal and Burkina Faso. Thus, an intercomparison between the satellite observations and the in situ measurements shows a good correlation between MODIS and AERONET with a correlation coefficient R = 0.86 at Cinzana, R = 0.85 at Banizounbou, R = 0.84 at Ouagadougou and a low correlation coefficient R = 0.66 calculated on the Dakar site. Like MODIS, SeaWiFS shows a very good correspondence with measurements of the ground photometer especially for Banizoumbou (R = 0.89), Cinzana (R = 0.88) and Dakar (R = 0.75) followed by a low correlation coefficient calculated on the Ouagadougou site (R = 0.64). The performance of these airborne sensors is also corroborated by the calculation of root mean square error (RMSE) and the mean absolute error (MAE). Following this validation, a climatological analysis based on aerosol optical depth (AOD) shows the seasonality of aerosols in West Africa strongly influenced by the climate dynamics illustrated by the MERRA model reanalysis. This seasonal spatial distribution of aerosols justifies the temporal variability of the particles observed at the different sites in the Sahel. In addition, a combined analysis of AOD and Angstrom coefficient indicates the aerosol period in the Sahel in spring (March-April-May) and summer (June-July-August). However, these aerosols are strongly dominated by desert dust whose main sources are located north in the Sahara and Sahel.