Impact of Covid-19 Pandemic on Atmospheric Environment over China: A Satellite Perspective

The Coronavirus Disease 2019 (COVID-19) pandemic, which has lasted for more than two years, has had a huge impact on human health and the global economy, as well as the ecological environment. In this study, the variations of atmospheric environment over China from 2019 to 2020 were calculated and analyzed based on the measured total columns of ozone (O-3), sulfur dioxide (SO2), nitrogen dioxide (NO2) and aerosol optical depth (AOD) from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite. The study shows the impact of the epidemic prevention and control measures and the resumption of work and production on atmospheric environment, and demonstrates that satellite remote sensing can play an important role in the monitoring of the COVID-19 pandemic, especially its impact on atmospheric environment.

Study on Spatial Changes in PM2.5 before and after the COVID-19 Pandemic in Southwest China

Coronavirus disease 2019 (COVID-19) swept the world at the beginning of 2020, and strict activity control measures were adopted in China's concentrated and local outbreak areas, which led to social shutdown. This study was conducted in southwest China from 2019 to 2021, and was divided into the year before COVID-19 (2019), the year of COVID-19 outbreak (2020), and the year of normalization of COVID-19 prevention and control (2021). A geographically and temporally weighted regression (GTWR) model was used to invert the spatial distribution of PM2.5 by combining PM2.5 on-site monitoring data and related driving factors. At the same time, a multiple linear regression (MLR) model was constructed for comparison with the GTWR model. The results showed that: (1) The inversion accuracy of the GTWR model was higher than that of the MLR model. In comparison with the commonly used PM2.5 datasets "CHAP” and "ACAG”, PM2.5 inverted by the GTWR model had higher data accuracy in southwest China. (2) The average PM2.5 concentrations in the entire southwest region were 32.1, 26.5, and 28.6 μg/m3 over the three years, indicating that the society stopped production and work and the atmospheric PM2.5 concentration reduced when the pandemic control was highest in 2020. (3) The winter and spring of 2020 were the relatively strict periods for pandemic control when the PM2.5 concentration showed the most significant drop. In the same period of 2021, the degree of control was weakened, and the PM2.5 concentration showed an upward trend.

The Effect of Abrupt Changes to Sources of PM 10 and PM 2.5 Concentrations in Three Major Agglomerations in Mexico

In the three major urban agglomerations in Mexico (Mexico City, Monterrey, and Guadalajara), a significant change to anthropogenic sources of air pollution happened in March–May 2020, when policies implemented to stop the spread of the COVID-19 virus in Mexico caused the reduction of some anthropogenic sources of air pollution. We study the effect of these significant changes to air pollution sources using satellite-retrieved aerosol optical depth (AOD) and particulate matter (PM10 and PM2.5) concentrations from ground stations. The Chow test was applied to study trend changes in PM concentrations from 1 January to 30 May 2020. The Mann–Whitney non-parametric test was then used to compare average PM concentrations in April and May pre-lockdown, during lockdown in 2020, and post-lockdown in 2021. The assessment was further performed by evaluating the exceedance of national air quality standard maxima. The trend analysis showed that PM10 concentrations were reduced during lockdown in Mexico City and Monterrey, whereas no change was found for PM10 in Guadalajara and PM2.5 in the three cities. Further analysis showed that in Mexico City and Guadalajara, average PM10 and PM2.5 concentrations decreased by 12% in April and May 2020. However, in Monterrey, average PM10 and PM2.5 concentrations increased by 2.76% and 11.07%, respectively, in April 2021 due to a severe drought that caused dry soils and dust around the city. The results of this research can be used to implement policies for reducing anthropogenic sources to improve the air quality in urban areas. [ABSTRACT FROM AUTHOR] Copyright of Atmosphere is the property of MDPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Effect of Transportation Operation on Air Quality in China Based on MODIS AOD during the Epidemic

With the rapid growth of automobile numbers and the increased traffic congestion, traffic has increasingly significant effects on regional air quality and regional sustainable development in China. This study tried to quantify the effect of transportation operation on regional air quality based on MODIS AOD. This paper analyzed the space-time characteristics of air quality and traffic during the epidemic by series analysis and kernel density analysis, and quantified the relationship between air quality and traffic through a Geographically Weighted Regression (GWR) model. The main research conclusions are as follows: The epidemic has a great impact on traffic and regional air quality. PM2.5 and NO2 had the same trend with traffic congestion delay index (CDI), but they were not as obvious as CDI. Both cities with traffic congestion and cities with the worst air quality showed strong spatial dependence. The concentration areas of high AOD value in the east areas of the Hu line were consistent with the two gathering centers formed by cities with traffic congestion in space, and also consistent with the gathering center of cities with poor air quality. The concentration area of AOD decline was consistent with the gathering center formed by cities with the worst air quality. AOD had a strong positive correlation with road network density, and its GWR correlation coefficient was 0.68, then These provinces suitable for GWR or not suitable were divided. This study has a great significance for the transportation planning, regional planning, air quality control strategies and regional sustainable development, etc.

Evaluating TROPOMI and MODIS performance to capture the dynamic of air pollution in São Paulo state: A case study during the COVID-19 outbreak.

Atmospheric pollutant data retrieved through satellite sensors are continually used to assess changes in air quality in the lower atmosphere. During the COVID-19 pandemic, several studies started to use satellite measurements to evaluate changes in air quality in many different regions worldwide. However, although satellite data is continuously validated, it is known that its accuracy may vary between monitored areas, requiring regionalized quality assessments. Thus, this study aimed to evaluate whether satellites could measure changes in the air quality of the state of São Paulo, Brazil, during the COVID-19 outbreak; and to verify the relationship between satellite-based data [Tropospheric NO2 column density and Aerosol Optical Depth (AOD)] and ground-based concentrations [NO2 and particulate material (PM; coarse: PM10 and fine: PM2.5)]. For this purpose, tropospheric NO2 obtained from the TROPOMI sensor and AOD retrieved from MODIS sensor data by using the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm were compared with concentrations obtained from 50 automatic ground monitoring stations. The results showed low correlations between PM and AOD. For PM10, most stations showed correlations lower than 0.2, which were not significant. The results for PM2.5 were similar, but some stations showed good correlations for specific periods (before or during the COVID-19 outbreak). Satellite-based Tropospheric NO2 proved to be a good predictor for NO2 concentrations at ground level. Considering all stations with NO2 measurements, correlations >0.6 were observed, reaching 0.8 for specific stations and periods. In general, it was observed that regions with a more industrialized profile had the best correlations, in contrast with rural areas. In addition, it was observed about 57% reductions in tropospheric NO2 throughout the state of São Paulo during the COVID-19 outbreak. Variations in air pollutants were linked to the region economic vocation, since there were reductions in industrialized areas (at least 50% of the industrialized areas showed >20% decrease in NO2) and increases in areas with farming and livestock characteristics (about 70% of those areas showed increase in NO2). Our results demonstrate that Tropospheric NO2 column densities can serve as good predictors of NO2 concentrations at ground level. For MAIAC-AOD, a weak relationship was observed, requiring the evaluation of other possible predictors to describe the relationship with PM. Thus, it is concluded that regionalized assessment of satellite data accuracy is essential for assertive estimates on a regional/local level. Good quality information retrieved at specific polluted areas does not assure a worldwide use of remote sensor data.

Decade-low aerosol levels over the Bohai and Yellow Seas amid the COVID-19 lockdown.

Coronavirus disease 2019 (COVID-19) has crucially influenced anthropogenic activities, which in turn impacts upon the environment. In this study, we investigated the variations on aerosol optical depth (AOD) at 550 nm over the Bohai Sea and Yellow Sea during the COVID-19 lockdown (from February to March in 2020) of China mainland based on Moderate-resolution Imaging Spectroradiometer (MODIS) observation by comparing with historical AOD records (2011-2019). Our results show that with the lockdown implementation, the decade-low AOD levels are achieved in February and March 2020 (0.39 ± 0.18 and 0.37 ± 0.19, respectively), which are 22% and 28% (p < 0.01) lower than the average AOD between 2011 and 2019 (0.50 ± 0.08 and 0.52 ± 0.05, respectively). After the lockdown restrictions were relaxed and industrial production gradually resumed, the AOD in April 2020 rebounded to the historical average level. Besides, compared with historical observations (2011-2019), the AOD temporal variability from February to April 2020 showed different pattern, with the decade-high increase from March to April (+0.11) and decade-low increase from February to March (-0.01). Independent observations and simulation, including fine particulate matter (PM2.5) from ground-based measurements, wind field from Cross-Calibrated Multi-Platform, satellite-derived aerosol type, and back trajectories calculation by Hybird Single Paricle Lagrangian Intergrated Trajectory (HYSPLIT) model, indicated that the above abnormal AOD variation can be attributed to reduction of anthropogenic emissions during the COVID-19 lockdown period. The results of this paper, therefore, indicate that aerosols over the Bohai and Yellow Seas are strongly influenced by human activities, and the public health events such as the epidemic may alter the intensity of human activities and thus the spatio-temporal pattern of aerosol over ocean. With the global spread of the epidemic and the corresponding significant changes in human behavior patterns (restrictions on human activities, etc.), more studies should be carried out in the future about the aerosol variability and its potential impact on the marine environment.

An assessment of aerosol optical depth over three AERONET sites in South Africa during the year 2020.

It is important to notice that the world health organization (WHO) on  the 11th of March 2020,  declared COVID-19 a global pandemic and in response governments around the world introduced lockdowns that restricted human and traffic movements including South Africa. This pandemic resulted in a total lockdown from 26 March until 16 April 2020 in South Africa with expected  decrease in atmospheric aerosols. In this present study,  the aerosol optical depth (AOD) over Southern Africa based on ground-based remotely sensed data derived from three AERONET sites (Durban, Skukuza and Upington) during 2020 were used to detrermine the restriction resopnse on atmospheric aerosol pollution  The study used data from 2019, 2018 and 2017  as base years. The AERONET derived data was complemented with the HYSPLIT Model and NCEP/NCAR Reanalysis data. The study findings show that peak increase of AOD corresponds to Angstrom exponent (AE) enhancement for two sites Durban and Skukuza during winter (JJA) while the Upington site showed a different trend where peak AOD were observed in spring (SON). The study also observed the influence of long transport airmasses particularly those originating from the Atlantic and Indian ocean moreso for the Durban and Skukuza sites (summer and autumn) thus these sites received fresh marine aerosols however this was not the case for Upington which fell under the influence of short-range inland airmasses and was likely to receive anthropogenic and dust aerosols. The major results  suggest that the lockdowns did not translate into a significant decrease in AOD levels compared to previous immediate years. The results has presented restriction response of AOD over South Africa but additional analysis is required using more locations to compare results.

Evolution of Pollution Levels from COVID-19 Lockdown to Post-Lockdown over India.

The spread of the COVID-19 pandemic forced the administration to lock down in many countries globally to stop the spread. As the lockdown phase had only the emergency use of transportation and most of the industries were shut down, there was an apparent reduction in pollution. With the end of the lockdown period, pollution is returning to its regular emission in most places. Though the background was abnormally low in emissions (during the lockdown phase) and the reduced pollution changed the radiation balance in the northern hemispheric summer period, a modified pollution pattern is possible during the unlock phases of 2020. The present study analysed the unlock 1 and 2 stages (June-July) of the COVID-19 lockdown over India. The rainfall, surface temperature and cloud cover anomalies of 2020 for understanding the differences in pollutants variation were also analysed. The unlock phases show remarkable differences in trends and mean variations of pollutants over the Indian region compared to climatological variations. The results indicated changing high-emission regions over India to climatological variations and identified an AOD dipole with future emissions over India.

COVID-19 Pandemic and Urban Air Quality: Delhi Region

COVID-19 pandemic hit the world bringing socio-economic and cultural shutdown of activities. The curse was a blessing to the environment in terms of significant air quality improvements. The study uses geospatial technology for assessing the reduction in nitrogen dioxide (NO2) levels and aerosol optical depth (AOD) levels using satellite-based (Sentinel-5P TROPOMI and MODIS data, respectively) and ground-based (Central Pollution Control Board, etc.) observations of 2019 and 2020. The study examines the lockdown period-wise reductions in ambient air pollution in the Delhi Region- the capital of India. It was investigated that satellite observations recorded a reduction of 51% in NO2 during lockdown phase-1 as compared to the pre-lockdown phase in 2020. When compared with 2019, the maximum reduction of 66.5% was seen in the lockdown phase-1, with p < 0.001. The ground-based stations also showed a 61% reduction in daily NO2 during lockdown phase-1 and phase-2 as compared to 2019. There is a drop in AOD by 55, 24 and 30% in lockdown phase-1, lockdown phase-2 and lockdown phase-3 w.r.t. pre-lockdown phases. However, an increase of 30% is observed during the post-lockdown phase of 2020 w.r.t. pre-lockdown phase. Ground-based stations ascertained that the reduction of 66, 60, 53 and 14% was observed in 2020 in the lockdown phases 1, 2 and 3 and post-lockdown phase w.r.t. pre-lockdown phase of 2020. Additionally, there is a 14, 56, 41, 39 and 3% reduction during the pre-lockdown, lockdown 1, lockdown 2, lockdown 3 and post-lockdown phase of 2020 w.r.t. similar periods of 2019. It was highlighted that environmental degradation can be mitigated with such stringent measures by policymakers from time to time to protect the deteriorating environment. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Impact of aerosols and reactive trace gases concentrations in India

The concentration of reactive trace gases in the atmosphere affects the human health differently. This study presents the changes of aerosol and reactive gases load in the atmosphere from the recent past with the help of Copernicus Atmosphere Monitoring Service (CAMS) data in Indian domain. The EAC4 (ECMWF Atmospheric Composition Reanalysis 4) data sets were used to examine spatially the load of ambient trace gases (NO2, O3, SO2 & CO) and aerosol present in the atmosphere as aerosol optical depth(AOD). The four weekly phases of the study are for April, 2020 (01-07, 08-14, 15-21 & 22-30). It has been observed during the above said phases that the concentration of aerosols, chemically reactive gases and greenhouse gases shows appreciable reduction up to ~60-70 % from CAMS Long Period Average (LPA) 17 years (2003-2019) data over the entire Indian sub-continent, except few pockets of Central (Durg, Indore, Bilaspuretc.) and South West (Kolhapur, Gujaratetc.) India. These slightly higher values in 2nd and 3rd week of April-2020 are due to pre-monsoon dust storm activity and well captured in vertical air flow Omega at 850/NCAR reanalysis. Concentrations of reactive gases from 12 different Central Pollution Control Board (CPCB) stations of India with CAMS, LPA data of April-2019 & 2020 has been compared and show that aerosol load in terms of PM-2.5 & PM-10 is appreciably drop down (60-70 %) over IGP and 25-30 % in other parts of India. The concentration of other reactive gases (NO2, SO2 & CO) with actual data from the month of April, 2019 &2020 also decreases ~ 32 %, 7 %, 17 % over IGP and 16 %, 8 %, 9 % in other parts of India respectively. The concentration of Ozone shows slightly positive behaviour over IGP and negative at other parts of India. This study is further brought out a message for future that we should use the natural resources judiciously as their long term exposure can cause severe health problems and a psychological burden or stress globally during this COVID-19 spread period. © 2022, India Meteorological Department. All rights reserved.

First-in-Human Study to Evaluate Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of a Rapidly Developed SARS-CoV-2 Therapeutic Antibody, AOD01, in Healthy Adults.

INTRODUCTION: AOD01 is a novel, fully human immunoglobulin (Ig) G1 neutralizing monoclonal antibody that was developed as a therapeutic against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). This first-in-human study assessed safety, tolerability, pharmacokinetics (PK), and pharmacodynamics of AOD01 in healthy volunteers. METHODS: Intravenous doses of AOD01 were evaluated in escalating cohorts [four single-dose cohorts (2, 5, 10, and 20 mg/kg) and one two-dose cohort (two doses of 20 mg/kg, 24 h apart)]. RESULTS: Twenty-three subjects were randomized to receive AOD01 or a placebo in blinded fashion. A total of 34 treatment-emergent adverse events (TEAEs) were reported; all were mild in severity. Related events (headache and diarrhea) were reported in one subject each. No event of infusion reactions, serious adverse event (SAE), or discontinuation due to AE were reported. The changes in laboratory parameters, vital signs, and electrocardiograms were minimal. Dose-related exposure was seen from doses 2 to 20 mg/kg as confirmed by Cmax and AUC0-tlast. The median Tmax was 1.5-3 h. Clearance was dose independent. Study results revealed long half-lives (163-465 h). Antidrug antibodies (ADA) to AOD01 were not detected among subjects, except in one subject of the two-dose cohort on day 92. Sustained ex vivo neutralization of SARS-CoV-2 was recorded until day 29 with single doses from 2 to 20 mg/kg and until day 43 with two doses of 20 mg/kg. CONCLUSIONS: AOD01 was safe and well tolerated, demonstrated dose-related PK, non-immunogenic status, and sustained ex vivo neutralization of SARS-CoV-2 after single intravenous dose ranging from 2 to 20 mg/kg and two doses of 20 mg/kg and show good potential for treatment of SARS-CoV-2 infection. (Health Sciences Authority identifier number CTA2000119).

Lockdown-induced Urban Aerosol Change over Changchun, China During COVID-19 Outbreak with Polarization LiDAR.

Depending on various government policies, COVID-19 (Corona Virus Disease-19) lockdowns have had diverse impacts on global aerosol concentrations. In 2022, Changchun, a provincial capital city in Northeast China, suffered a severe COVID-19 outbreak and implemented a very strict lockdown that lasted for nearly two months. Using ground-based polarization Light Detection and Ranging (LiDAR), we detected real-time aerosol profile parameters (EC, extinction coefficient; DR, depolarization ratio; AOD, aerosol optical depth), as well as air-quality and meteorological indexes from 1 March to 30 April in 2021 and 2022 to quantify the effects of lockdown on aerosol concentrations. The period in 2022 was divided into three stages: pre-lockdown (1-10 March), strict lockdown (11 March to 10 April), and partial lockdown (11-30 April). The results showed that, during the strict lockdown period, compared with the pre-lockdown period, there were substantial reductions in aerosol parameters (EC and AOD), and this was consistent with the concentrations of the atmospheric pollutants PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 µm) and PM10 (particulate matter with an aerodynamic diameter ≤ 10 µm), and the O3 concentration increased by 8.3%. During the strict lockdown, the values of EC within 0-1 km and AOD decreased by 16.0% and 11.2%, respectively, as compared to the corresponding period in 2021. Lockdown reduced the conventional and organized emissions of air pollutants, and it clearly delayed the time of seasonal emissions from agricultural burning; however, it did not decrease the number of farmland fire points. Considering meteorological factors and eliminating the influence of wind-blown dust events, the results showed that reductions from conventional organized emission sources during the strict lockdown contributed to a 30% air-quality improvement and a 22% reduction in near-surface extinction (0-2 km). Aerosols produced by urban epidemic prevention and disinfection can also be identified using the EC. Regarding seasonal sources of agricultural straw burning, the concentrated burning induced by the epidemic led to the occurrence of heavy pollution from increased amounts of atmospheric aerosols, with a contribution rate of 62%. These results indicate that there is great potential to further improve air quality in the local area, and suggest that the comprehensive use of straw accompanied by reasonable planned burning is the best way to achieve this.

Cumulative effects of air pollution and climate drivers on COVID-19 multiwaves in Bucharest, Romania.

Over more than two years of global health crisis due to ongoing COVID-19 pandemic, Romania experienced a five-wave pattern. This study aims to assess the potential impact of environmental drivers on COVID-19 transmission in Bucharest, capital of Romania during the analyzed epidemic period. Through descriptive statistics and cross-correlation tests applied to time series of daily observational and geospatial data of major outdoor inhalable particulate matter with aerodynamic diameter ≤ 2.5 µm (PM2.5) or ≤ 10 µm (PM10), nitrogen dioxide (NO2), ozone (O3), sulfur dioxide (SO2), carbon monoxide (CO), Aerosol Optical Depth at 550 nm (AOD) and radon (222Rn), we investigated the COVID-19 waves patterns under different meteorological conditions. This study examined the contribution of individual climate variables on the ground level air pollutants concentrations and COVID-19 disease severity. As compared to the long-term average AOD over Bucharest from 2015 to 2019, for the same year periods, this study revealed major AOD level reduction by ~28 % during the spring lockdown of the first COVID-19 wave (15 March 2020-15 May 2020), and ~16 % during the third COVID-19 wave (1 February 2021-1 June 2021). This study found positive correlations between exposure to air pollutants PM2.5, PM10, NO2, SO2, CO and 222Rn, and significant negative correlations, especially for spring-summer periods between ground O3 levels, air temperature, Planetary Boundary Layer height, and surface solar irradiance with COVID-19 incidence and deaths. For the analyzed time period 1 January 2020-1 April 2022, before and during each COVID-19 wave were recorded stagnant synoptic anticyclonic conditions favorable for SARS-CoV-2 virus spreading, with positive Omega surface charts composite average (Pa/s) at 850 mb during fall- winter seasons, clearly evidenced for the second, the fourth and the fifth waves. These findings are relevant for viral infections controls and health safety strategies design in highly polluted urban environments.

Aerosol Characteristics during the COVID-19 Lockdown in China: Optical Properties, Vertical Distribution, and Potential Source

The concentration changes of aerosols have attracted wide-ranging attention during the COVID-19 lockdown (CLD) period, but the studies involving aerosol optical properties (AOPs) are relatively insufficient, mainly AOD (fine-mode AOD (AODf) and coarse-mode AOD (AODc)), aerosol absorption optical depth (AAOD), and aerosol extinction coefficient (AEC). Here, the remote-sensing observations, Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) products, backward-trajectory, and potential-source-contribution models are used to assess the impact of AOPs, vertical distribution, and possible sources on the atmosphere environment in North China Plain (NCP), Central China (CC), Yangtze River Delta (YRD), Pearl River Delta (PRD), and Sichuan Basin (SB) during the CLD period. The results demonstrate that both AOD (MODIS) and near-surface AEC (CALIPSO, <2 km) decreased in most areas of China. Compared with previous years (average 2017–2019), the AOD (AEC) of NCP, CC, YRD, PRD, and SB reduced by 3.33% (10.76%), 14.36% (32.48%), 10.80% (29.64%), 31.44% (22.68%), and 15.50% (8.44%), respectively. In addition, MODIS (AODc) and MERRA-2 (AODc) decreased in the five study areas compared with previous years, so the reduction in dust activities also contributed to improving regional air quality during the epidemic. Despite the reduction of anthropogenic emissions (AODf) in most areas of China during the CLD periods, severe haze events (AODf > 0.6) still occurred in some areas. Compared to previous years, there were increases in BC, OC (MERRA-2), and national raw coal consumption during CLD. Therefore, emissions from some key sectors (raw coal heating, thermal power generation, and residential coal) did not decrease, and this may have increased AODf during the CLD. Based on backward -rajectory and potential source contribution models, the study area was mainly influenced by local anthropogenic emissions, but some areas were also influenced by northwestern dust, Southeast Asian biomass burning, and marine aerosol transport. This paper underscores the importance of emissions from the residential sector and thermal power plants for atmospheric pollution in China and suggests that these sources must be taken into account in developing pollution-mitigation plans. [ FROM AUTHOR] Copyright of Remote Sensing is the property of MDPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

Beyond the lockdowns: satellite observations of aerosol optical depth through 2020, the first year of the COVID-19 pandemic

Anticipated future reductions in aerosol emissions are expected to accelerate warming and substantially change precipitation characteristics. Therefore, it is vital to identify the existing patterns and possible future pathways of anthropogenic aerosol reductions. The COVID-19 pandemic prompted abrupt, global declines in transportation and industrial activities, providing opportunities to study the aerosol effects of pandemic-driven emissions changes. Here, measurements of aerosol optical depth (AOD) from two satellite instruments were used to characterize aerosol burdens throughout 2020 in four Northern Hemisphere source regions (Eastern & Central China, the United States, India, and Europe). In most regions, record-low measures of AOD persisted beyond the earliest ‘lockdown’ periods of the pandemic. Record-low values were most concentrated during the boreal spring and summer months, when 56% to 72% of sampled months showed record-low AOD values for their respective regions. However, in India and Eastern & Central China, the COVID-19 AOD signature was eclipsed by sources of natural variability (dust) and a multi-year trend, respectively. In the United States and Europe, a likely COVID-19 signal peaks in the summer of 2020, contributing as much as −.01 to −.03 AOD units to observed anomalies.

Variations of Aerosol Radiative Forcing During Covid-19 Imposed Lockdown Over Ahmedabad City

In the present study Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua and Terra satellite derived Aerosol Optical Depth (AOD) and the Ozone Monitoring Instrument (OMI) onboard Aura satellite derived Single Scattering Albedo (SSA) data sets were used to demonstrate the regional variation in aerosol radiative forcing during covid-19 imposed lockdown over the urban climate of Ahmedabad city. An analysis of short-wave (0.25um to 4.0 um) Instantaneous Direct Aerosol Radiative forcing (IDARF) is done using these satellite data as inputs to the Radiative Transfer model - SBDART. Result shows reduction in IDARF by the month of April-2020 and highest reduction in the month of May. Value of IDARF for May is around 22.785 Wm-2, which is 40.21% less than the mean value of IDARF from pre lockdown to post lockdown. Which indicates Negative Radiative Forcing (Net Cooling Effect). Magnitude of IDARF during lockdown and post lockdown are found to be 34.49 Wm-2 and 71.62 Wm-2 which is 87.94% higher than the mean value of IDARF from pre lockdown to post lockdown. Which suggest Positive Radiative Forcing (Net Warming Effect). © 2021 IEEE.

Effects of COVID-19 pandemic lockdown: A satellite data-based appraisal of air quality in Guwahati, Assam.

Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) based data are used to evaluate the effects of the COVID-19 lockdown on the concentrations of pollutants such as aerosol optical depth (AOD) and tropospheric columns of nitrogen dioxide (NO2) along with sulfur dioxide (SO2) respectively for the period of January 2017 to September 2021 over the capital city of Assam, Guwahati. In India lockdown due to COVID-19 was first imposed from 24th March to 14th April as phase I and then it extended from 15th April to 3rd May as phase II in the year 2020. The concentration of all pollutants was usually fall during the lockdown period as compared to their average during the 5-year period over the study area. The results showed that Pre-monsoon (March-May) seasonal AOD for the pandemic year 2020 was decreased by âˆ¼ 23% after lockdown as compared to same season of normal years over the study location. The seasonally averaged AOD reached its peak value in pre-monsoon (0.78 ± 0.09), followed by winter (0.59 ± 0.10) and monsoon (0.52 ± 0.05), with the minimum taking place in post-monsoon (0.38 ± 0.08) season. The monthly average AOD varies from its highest value (0.82 ± 0.18) in May to its lowest value (0.36 ± 0.10) in October for the study period over Guwahati. Tropospheric column NO2 exhibits same seasonality as AOD with highest value (0.21 × 1016 molecules cm-2) in pre-monsoon and lowest value (0.13 × 1016 molecules cm-2) in post-monsoon season which may be due to same source of origination of both NO2 and AOD. Conversely, SO2 does not vary much from the five-year average value during the lockdown period. Significant reduction in PM2.5 mass concentration value during Covid-19 lockdown months has been observed which indicates short term improvement of air quality over Guwahati.

VARIATION OF SATELLITE-DERIVED AEROSOL OPTICAL DEPTH OVER CHINA BEFORE AND AFTER THE COVID-19 PANDEMIC

Due to the Coronavirus Disease (COVID-19) pandemic, the human activities in China and even in the world were reduced in 2020, which also caused the variation of the atmospheric environment, especially atmospheric aerosol emissions. In this paper, the MODIS level-3 gridded atmosphere monthly global joint product in 2019 and 2020 were collected and processed. After preliminary analysis, we found that MODIS annual aerosol optical depth (AOD) over China in 2020 is generally lower than in 2019. In some regions such as Beijing-Tianjin-Hebei and Yangtze River Delta, AOD values dropped the most in February. However, in some months and regions, AOD in 2020 is even higher than in 2019. More studies are still ongoing. © 2021 IEEE.

Use of MODiS-MAiAC (aod) Satellite Images as Qualitative Indicators of the Concentration of Particulate Matter pm2.5 in Bogota City

Particulate matter is the most-related contaminant to respiratory and cardiac diseases in the planet. In Colombia, it is frequently monitored as concentration of PM25 with air quality stations, that are run by government organizations. In addition to monitoring in some countries, the use of satellite images with AOD (Aerosol Optical Depth) has recently become popular to estimate PM2y however, in Colombia, this alternative has not been explored yet. This research seeks to assess the potential use of MODIS-MAIAC images as a qualitative indicator for PMj5 with data of two dates on a normal day and low mobility associated to the quarantine of the Bogota mayor's office by Covid-19. For the data of the two dates, correlations were found between the AOD and the PM25 of 0.60 and 0.62. Interpolation maps were made with the data for PM25, which gave acceptable results. © 2022, Universidad Nacional de Colombia. All rights reserved.

Phase-Resolved Lockdown Features of Pollution Parameters Over an Urban and Adjoining Rural Region During COVID-19

In this study, we investigate the temporal variations in columnar aerosol pollutants and their possible association with the simultaneously measured black carbon (BC) aerosol mass concentration and associated biomass burning (BB) over urban (Delhi) and rural (Panchgaon) sites during the lockdown phases of the COVID-19 pandemic. We also show the impact of lockdown measures on boundary layer ozone and its primary precursors, NO2, and water vapor (H2O), potent greenhouse gases that destroy protective ozone. For this purpose, we used multiple datasets, namely, black carbon (BC) aerosol mass concentration and biomass burning (BB) aerosols using an aethalometer at Amity University Haryana (AUH), Panchgaon, India, and satellite retrievals from NASA’s MODIS and OMI at both the stations. The analysis was conducted during the pre-lockdown period (1–25 March), lockdown 1st phase (25 March–14 April), lockdown 2nd phase (15 April–3 May), lockdown 3rd phase (4–17 May), lockdown 4th phase (18–31 May), and post-lockdown (1–30 June) period in 2020. Our diagnostic analysis shows a substantial reduction in AOD (Delhi: −20% to −80%, Panchgaon: −20% to −80%) and NO2 (Delhi: −10% to −42.03%, Panchgaon −10% to −46.54%) in comparison with climatology (2010–2019) during all four phases of lockdown. The reduction in AOD is attributed to lockdown measures and less transport of dust from west Asia than climatology. Despite a reduction in NO2, there is an increase in the ozone amount (Delhi: 1% to 8% and Panchgaon: 1% to 10%) during lockdown I, II, and III phases. The observed enhancement in ozone may be resultant from the complex photochemical processes that involve the presence of NO2, CO, volatile organic compounds (VOCs), and water vapor. The reduction in AOD and NO2 and enhancement in ozone are stronger at the rural site, Panchgaon than that at the urban site, Delhi. Copyright © 2022 Sonbawne, Fadnavis, Vijayakumar, Devara and Chavan.