scholarly journals Impact of the COVID-19 pandemic related to lockdown measures on tropospheric NO<sub>2</sub> columns over Île-de-France

2021 ◽  
Vol 21 (24) ◽  
pp. 18303-18317
Author(s):  
Andrea Pazmiño ◽  
Matthias Beekmann ◽  
Florence Goutail ◽  
Dmitry Ionov ◽  
Ariane Bazureau ◽  
...  
Keyword(s):  
Linear Trend ◽  
Surface Concentration ◽  
Urban Site ◽  
Data Sets ◽  
Air Masses ◽  
Tropospheric No2 ◽  
Surface Measurements ◽  
Uv Visible ◽  
The Impact ◽  
Suburban Site

Abstract. The evolution of NO2, considered as a proxy for air pollution, was analyzed to evaluate the impact of the first lockdown (17 March–10 May 2020) over the Île-de-France region (Paris and surroundings). Tropospheric NO2 columns measured by two UV-Visible Système d'Analyse par Observation Zénithale (SAOZ) spectrometers were analyzed to compare the evolution of NO2 between urban and suburban sites during the lockdown. The urban site is the observation platform QualAir (48∘50′ N / 2∘21′ E) at the Sorbonne University Pierre and Marie Curie Campus in the center of Paris. The suburban site is located at Guyancourt (48∘46′N / 2∘03′E), Versailles Saint-Quentin-en-Yvelines University, 24 km southwest of Paris. Tropospheric NO2 columns above Paris and Guyancourt have shown similar values during the whole lockdown period from March to May 2020. A decade of data sets were filtered to consider air masses at both sites with similar meteorological conditions. The median NO2 columns and the surface measurements of Airparif (Air Quality Observatory in Île de France) during the lockdown period in 2020 were compared to the extrapolated values estimated from a linear trend analysis for the 2011–2019 period at each station. Negative NO2 trends of −1.5 Pmolec. cm−2 yr−1 (∼ −6.3 % yr−1) are observed from the columns, and trends of −2.2 µg m−3 yr−1 (∼ −3.6 % yr−1) are observed from the surface concentration. The negative anomaly in tropospheric columns in 2020 attributed to the lockdown (and related emission reductions) was found to be 56 % at Paris and 46 % at Guyancourt, respectively. A similar anomaly was found in the data of surface concentrations, amounting to 53 % and 28 % at the urban and suburban sites, accordingly.

scholarly journals Impact of COVID-19 pandemic related to lockdown measures on tropospheric NO<sub>2</sub> columns over Île-de-France

2021 ◽  
Author(s):  
Andrea Pazmiño ◽  
Matthias Beekmann ◽  
Florence Goutail ◽  
Dmitry Ionov ◽  
Ariane Bazureau ◽  
...  
Keyword(s):  
Linear Trend ◽  
Surface Concentration ◽  
Urban Site ◽  
Air Masses ◽  
South West ◽  
Tropospheric No2 ◽  
Surface Measurements ◽  
Uv Visible ◽  
The Impact ◽  
Suburban Site

Abstract. The evolution of NO2, considered as proxy for air pollution, was analyzed to evaluate the impact of 1st lockdown (March 17th – May 10th 2020) over île-de-France region (Paris and surroundings). Tropospheric NO2 columns measured by two UV-Visible SAOZ spectrometers were analyzed to compare the evolution of NO2 between urban and suburban sites during the lockdown. The urban site is the observation platform QUALAIR (48°50' N/2°21' E) on the Pierre et Marie Curie Campus of Sorbonne University in the center of Paris. The suburban site is located at Guyancourt (48°46' N/2°03' E), University of Versailles Saint Quentin, 24 km south-west of Paris. Tropospheric NO2 columns above Paris and Guyancourt have shown similar values during the whole lockdown period from March to May 2020. One decade datasets were filtered to consider air masses at both sites with similar meteorological conditions. The median NO2 columns, as well as the surface measurements of AIPARIF (Air Quality Observatory in Ile de France) during the lockdown period in 2020 were compared to the extrapolated values estimated from a linear trend analysis for the 2011–2019 period at each station. Negative NO2 trends of −1.5 Pmolec cm−2 yr−1 (~−6.3 % yr−1) are observed from the columns and of −2.2 μg m−3 yr−1 (~−3.6 % yr−1) from the surface concentration. The negative anomaly in tropospheric columns in 2020 attributed to lockdown (and related emission reductions) was found to be 56 % at Paris and 46 % at Guyancourt, respectively. Similar anomaly was found in the data of surface concentrations, amounting for 53 % and 28 % at the urban and suburban sites, accordingly.

scholarly journals Reduction of Air Pollution in Poland in Spring 2020 during the Lockdown Caused by the COVID-19 Pandemic

2021 ◽  
Vol 13 (18) ◽  
pp. 3784
Author(s):  
Patryk Tadeusz Grzybowski ◽  
Krzysztof Mirosław Markowicz ◽  
Jan Paweł Musiał
Keyword(s):  
Air Pollution ◽  
Ground Level ◽  
Weather Conditions ◽  
Well Being ◽  
Urban Site ◽  
Number Density ◽  
Air Masses ◽  
Tropospheric No2 ◽  
Clean Air ◽  
Column Number

The COVID-19 pandemic has affected many aspects of human well-being including air quality. The present study aims at quantifying this effect by means of ground-level concentrations of NO2, PM2.5, as well as aerosol optical depth (AOD) measurements and tropospheric NO2 column number density (NO2 TVCD), during the imposed governmental restrictions in spring 2020. The analyses were performed for both urban and non-built-up areas across the whole of Poland accompanied by Warsaw (urban site) and Strzyzow (a background site). The results revealed that mean PM2.5 concentrations in spring 2020 for urban and non-built-up areas across Poland and for Warsaw were 20%, 23%, 15% lower than the 10-year average, respectively. Analogous mean NO2 concentrations were lower by 20%, 18%, 30% and NO2 TVCD revealed 9%, 4%, 9% reductions in 2020 as compared to 2019. Regarding mean AOD, retrieved from MERRA-2 reanalysis, it was found that for the whole of Poland during spring 2020 the reduction in AOD as compared to the 10-year average was 15%. The contribution of the lockdown within total air pollution reduction is not easily assessable due to anomalous weather conditions in 2020 which resulted in advection of clean air masses identified from MERRA-2 reanalysis and Strzyzow observatory.

scholarly journals Tropospheric NO<sub>2</sub> column densities deduced from zenith-sky DOAS measurements in Shanghai, China, and their application to satellite validation

2008 ◽  
Vol 8 (4) ◽  
pp. 16713-16762 ◽  
Author(s):  
D. Chen ◽  
B. Zhou ◽  
S. Beirle ◽  
L. M. Chen ◽  
T. Wagner
Keyword(s):  
Solar Zenith Angle ◽  
Surface Concentration ◽  
Urban Site ◽  
Optical Absorption Spectroscopy ◽  
Vertical Column ◽  
Satellite Validation ◽  
Tropospheric No2 ◽  
Realistic Information ◽  
Good Agreement

Abstract. Zenith-sky scattered sunlight observations using differential optical absorption spectroscopy (DOAS) technique were carried out in Shanghai, China (31.3° N, 121.5° E) since December 2006. At this polluted urban site, the measurement provided NO2 total columns in the daytime. Here, we present a new method to extract time series of tropospheric vertical column densities (VCD) of NO2 from these observations. The derived tropospheric NO2 VCD is an important quantity for the estimation of emissions and for the validation of satellite observations. Our method makes use of assumptions on the relative NO2 height profiles and on the diurnal variation of the stratospheric NO2 VCD. The influence of these parameters on the retrieved tropospheric NO2 VCD is discussed; for a polluted site like Shanghai, the accuracy of our method is estimated to be <20% for solar zenith angle (SZA) lower than 85°. From simultaneously performed long-path DOAS measurement, the NO2 surface concentration at the same site was observed and the corresponding tropospheric NO2 VCD was estimated using the assumed seasonal NO2 profiles in the planetary boundary layer (PBL). By making a comparison between the tropospheric NO2 VCD from zenith-sky and long-path DOAS measurements, it was found that the former provided more realistic information about total tropospheric pollution than the latter, so it's more suitable for satellite data validation than the in situ measurement. A comparison between the tropospheric NO2 VCD from ground-based zenith-sky measurement and SCIAMACHY was also made. Satellite validation for a strongly polluted area is highly needed, but exhibits also a great challenge. Our comparison showed good agreement, considering in particular the different spatial resolutions between the two measurements.

scholarly journals Long-term visibility variation in Athens (1931–2013): A proxy for local and regional atmospheric aerosol loads

2016 ◽  
Author(s):  
Dimitra Founda ◽  
Stelios Kazadzis ◽  
Nikolaos Mihalopoulos ◽  
Evangelos Gerasopoulos ◽  
Maria Lianou
Keyword(s):  
Relative Humidity ◽  
Decadal Variability ◽  
Linear Trend ◽  
Recent Decade ◽  
Global Scale ◽  
Urban Site ◽  
Historical Archives ◽  
Surface Measurements ◽  
The 1950S

Abstract. This study explores the inter-decadal variability and trends of surface horizontal visibility at the urban area of Athens from 1931 to 2013, using the historical archives of the National Observatory of Athens (NOA). A prominent deterioration of visibility in the city was detected, with the long-term linear trend amounting to −2.8 km decade−1 (p < 0.001), over the entire studied period. This was not accompanied with any significant trend in relative humidity (RH) or precipitation over the same period. A slight recovery of visibility levels seems to be established in the recent decade (2004–2013). It was found that very good visibility (> 20 km) occurred at a frequency of 34 % before the 1950s, while this percentage drops to just 2 % during the recent decade. The rapid impairment of the visual air quality in Athens around 1950, points to the increased levels of air pollution from local and/or regional emission sources, related to high urbanization rates and/or higher rates of anthropogenic emissions increase on a global scale at that period. A marked seasonal cycle was detected in visibility before the 1950s, which attenuates afterwards. Visibility was found to be negatively/positively correlated with relative humidity (RH)/wind speed, the correlation being statistically valid at certain periods. Wind regime and mainly wind direction and corresponding air masses origin was found to highly control visibility levels in Athens. The comparison between visibility in Athens and at a reference, non urban site, revealed similar negative trends over the common period of observations, suggesting that apart from the contribution of local sources, visibility in Athens is highly determined by aerosol loads of regional origin. Satellite derived aerosol optical depth (AOD) retrievals over Athens since 2000, and surface measurements of PM10 confirmed the relation of visibility with aerosol loads.

scholarly journals Wintertime peroxyacetyl nitrate (PAN) in the megacity Beijing: the role of photochemical and meteorological processes

2012 ◽  
Vol 12 (12) ◽  
pp. 31871-31916 ◽  
Author(s):  
H. Zhang ◽  
X. Xu ◽  
W. Lin ◽  
Y. Wang
Keyword(s):  
Boundary Layer ◽  
Thermal Decomposition ◽  
Atmospheric Condition ◽  
Urban Site ◽  
Peroxyacetyl Nitrate ◽  
Air Masses ◽  
Photochemical Production ◽  
Hourly Concentration ◽  
Weak Winds ◽  
The Impact

Abstract. Peroxyacetyl nitrate (PAN) is one of the key photochemical pollutants and acts as an important reservoir for the peroxyacetyl (PA) radical and nitrogen oxides (NOx) over cold and less polluted regions. Previous measurements of PAN in Asian megacities were scarce and mainly conducted for relatively short periods in summer. In this study, we present and analyze the measurements of PAN, O3, NOx, CO, and some meteorological variables, made at an urban site (CMA) in Beijing from 25 January to 22 March 2010. During the observations, the hourly concentration of PAN varied from 0.23 to 3.51 ppb, with an average of 0.70 ppb. Both PAN and O3 showed small but significant diurnal cycle, with PAN peaking around 17:00 LT, three hours later than O3. The observed concentration of PAN is well correlated with that of NOx but not O3. These phenomena indicate that the variations of the winter concentrations of PAN and O3 in urban Beijing are decoupled with each other. Wind conditions and transport of air masses exert very significant impacts on O3, PAN, and other species. The strong WNW-N winds caused elevated concentrations of surface O3 and lower concentrations of PAN, NOx, and CO. Weak winds from the other directions led to enhanced levels of PAN, NOx, and CO and decreased level of O3. Air masses arriving at our site originated either from the boundary layer over the highly polluted N-S-W sector or from the free troposphere over the W-N sector. The descending free-tropospheric air was rich in O3, with an average PAN/O3 ratio smaller than 0.031, while the boundary layer air over the polluted sector contained higher levels of PAN and primary pollutants, with an average PAN/O3 ratio of 0.11. These facts related with meteorological conditions, specifically the air transport conditions, can well explain the observed PAN-O3 decoupling. The impact of meso-scale transport is demonstrated using a case during 21–22 February 2010. In addition to transport, photochemical production is important to PAN in the winter boundary layer over Beijing. The PA concentration is estimated from the measurements of PAN and related variables. The estimated PA concentration for three days with stable atmospheric condition, 7 February, 23 February, and 11 March, are in the range of 0–0.012, 0–0.036, and 0–0.040 ppt, respectively. We found that both the formation reaction and thermal decomposition contributed significantly to PAN's variation. The results here suggest that even in the colder period, both photochemical production and thermal decomposition of PAN in the polluted boundary layer over Beijing are not negligible, with the production exceeding the decomposition.

scholarly journals Reanalysis of and attribution to near-surface ozone concentrations in Sweden during 1990–2013

2017 ◽  
Vol 17 (22) ◽  
pp. 13869-13890 ◽  
Author(s):  
Camilla Andersson ◽  
Heléne Alpfjord ◽  
Lennart Robertson ◽  
Per Erik Karlsson ◽  
Magnuz Engardt
Keyword(s):  
Transport Model ◽  
Linear Trend ◽  
Surface Ozone ◽  
Vegetation Indices ◽  
High Sensitivity ◽  
Anthropogenic Emissions ◽  
Data Sets ◽  
Near Surface ◽  
The Impact ◽  
Surface O3

Abstract. We have constructed two data sets of hourly resolution reanalyzed near-surface ozone (O3) concentrations for the period 1990–2013 for Sweden. Long-term simulations from a chemistry-transport model (CTM) covering Europe were combined with hourly ozone concentration observations at Swedish and Norwegian background measurement sites using retrospective variational data analysis. The reanalysis data sets show improved performance over the original CTM when compared to independent observations. In one of the reanalyses, we included all available hourly near-surface O3 observations, whilst in the other we carefully selected time-consistent observations. Based on the second reanalysis we investigated statistical aspects of the distribution of the near-surface O3 concentrations, focusing on the linear trend over the 24-year period. We show that high near-surface O3 concentrations are decreasing and low O3 concentrations are increasing, which is reflected in observed improvement of many health and vegetation indices (apart from those with a low threshold). Using the CTM we also conducted sensitivity simulations to quantify the causes of the observed change, focusing on three factors: change in hemispheric background concentrations, meteorology and anthropogenic emissions. The rising low concentrations of near-surface O3 in Sweden are caused by a combination of all three factors, whilst the decrease in the highest O3 concentrations is caused by European O3 precursor emissions reductions. While studying the impact of anthropogenic emissions changes, we identified systematic differences in the modeled trend compared to observations that must be caused by incorrect trends in the utilized emissions inventory or by too high sensitivity of our model to emissions changes.

DAMPAK VOLATILITAS HARGA MINYAK DI INDONESIA TERHADAP PENYESUAIAN KESEIMBANGAN FISKAL

2015 ◽  
Vol 15 (2) ◽  
pp. 37-52
Author(s):  
Mahpud Sujai
Keyword(s):  
Linear Trend ◽  
The State ◽  
Oil Price ◽  
Output Gap ◽  
State Budget ◽  
Price Changes ◽  
Potential Output ◽  
Budget Cycle ◽  
Actual Output ◽  
The Impact

This paper is intended to analyze the effect of oil price changes on potential output and actual output in the state budget cycle and identifies the output gap which is the difference between potential output and actual output. The research methodology uses a quantitative approach to analyze problems that occur related to the impact of oil price changes to the state budget cycle. Data analysis was carried out through the approach cyclically adjusted fiscal balance with a simplified approach. This research identified that the potential output is likely to continue increasing in line with Indonesia's oil price trends which is continue to rise following the world oil price movements. In calculating the output gap using a linear trend and HP filter, the result is fuctuating depend on the percentage changes in both potential output and actual output. This paper concludes that Indonesian oil price (ICP) has a significant impact on changes in the state budget cycle. If oil prices rise, the output gap between potential output and actual output is greater, and vice versa. This will make the budget vulnerable to shock that occurs as an external infuence.

Impact of dust and sand storms on the aviation operation and assessment of conditions for their occurrence at aerodromes in European Russia

2020 ◽  
Vol 4 ◽  
pp. 78-95
Author(s):  
A.R. Ivanova ◽  
◽  
E.N. Skriptunova ◽  
N.I. Komasko ◽  
A.A. Zavialova ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Dust Storms ◽  
European Russia ◽  
Air Transport ◽  
Review Of Literature ◽  
Dust Transport ◽  
Air Masses ◽  
The Past ◽  
Sand Storm ◽  
The Impact

A review of literature on the impact of dust and sand storms on the air transport operation is presented. Observational data on dust storms at the aerodromes of European Russia for the period of 2001-2019 are analyzed. The seasonal variations in dust transport episodes at aerodromes and its relationship with visibility changes are discussed. The characteristics of dusty air masses and advection are given. It is concluded that the frequency of dust transfer episodes for the aerodromes under study has decreased over the past five years, except for Gumrak aerodrome (Volgograd). Keywords: dust storm, sand storm, aviation, visibility, seasonal variations, aerodrome оf European Russia

scholarly journals Investigating the impact of pre-processing techniques and pre-trained word embeddings in detecting Arabic health information on social media

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yahya Albalawi ◽  
Jim Buckley ◽  
Nikola S. Nikolov
Keyword(s):  
Social Media ◽  
Deep Learning ◽  
Comprehensive Evaluation ◽  
Classification Problem ◽  
Data Sets ◽  
Word Embeddings ◽  
Data Set ◽  
Lower Accuracy ◽  
Health Related ◽  
The Impact

AbstractThis paper presents a comprehensive evaluation of data pre-processing and word embedding techniques in the context of Arabic document classification in the domain of health-related communication on social media. We evaluate 26 text pre-processings applied to Arabic tweets within the process of training a classifier to identify health-related tweets. For this task we use the (traditional) machine learning classifiers KNN, SVM, Multinomial NB and Logistic Regression. Furthermore, we report experimental results with the deep learning architectures BLSTM and CNN for the same text classification problem. Since word embeddings are more typically used as the input layer in deep networks, in the deep learning experiments we evaluate several state-of-the-art pre-trained word embeddings with the same text pre-processing applied. To achieve these goals, we use two data sets: one for both training and testing, and another for testing the generality of our models only. Our results point to the conclusion that only four out of the 26 pre-processings improve the classification accuracy significantly. For the first data set of Arabic tweets, we found that Mazajak CBOW pre-trained word embeddings as the input to a BLSTM deep network led to the most accurate classifier with F1 score of 89.7%. For the second data set, Mazajak Skip-Gram pre-trained word embeddings as the input to BLSTM led to the most accurate model with F1 score of 75.2% and accuracy of 90.7% compared to F1 score of 90.8% achieved by Mazajak CBOW for the same architecture but with lower accuracy of 70.89%. Our results also show that the performance of the best of the traditional classifier we trained is comparable to the deep learning methods on the first dataset, but significantly worse on the second dataset.

scholarly journals Salt Intake in Nigeria: a nationwide population survey

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
A.N Odili ◽  
B.S Chori ◽  
B Danladi ◽  
P.C Nwakile ◽  
J.O Ogedengbe ◽  
...  
Keyword(s):  
Salt Intake ◽  
Sodium Intake ◽  
Population Analysis ◽  
Cost Effective ◽  
Rural Site ◽  
Urban Site ◽  
Funding Source ◽  
Salt Reduction ◽  
High Salt Intake ◽  
The Impact

Abstract Background Population wide salt reduction programmes are cost effective strategies for control of cardiovascular diseases (CVDs). Obtaining a nationwide salt consumption data in a multi-cultural setting as Nigeria's is key for proper implementation and monitoring of such strategy. Methods We measured sodium in 24-hour urine of free-living adult Nigerians selected from an urban and a rural site each from the 6 geopolitical zones of Nigeria to evaluate patterns of salt intake and its associations with blood pressures (BP). Results Across the 12 sites, sodium intake ranged from 97.9 in the rural South-South to 210 mmol/day in the urban site of the same zone. Overall, the median (IQR) daily sodium intake was 143.5 (97.8) mmol; with higher (p=0.0028) levels among the urban 149.7 (113.8) compared to the rural 133.1 (105.2) dwellers. Overall, 20% of the subjects consumed less than the recommended 2g (86mmol) of sodium daily. After adjustment for age, sex and BMI; sodium intake and BP (systolic and diastolic) were positively associated in 8 out of the 12 sites; significantly so in 2 (p&lt;0.05) for systolic. Within population analysis; which included 973 individuals, increasing sodium intake tended (not significantly) to increase SBP but decrease DBP. However, among subjects whose sodium intake was in excess of 257mmol/day, a 100 mmol/day increase in sodium intake was significantly (p=0.04) associated with a 3.3 mmHg increase in SBP. Conclusion Salt intake among Nigerians is higher than the recommended. The impact of sodium intake on BP appears to be evident only among individuals with high salt intake. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Wellcome Trust

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