Long-term trends of zonally averaged aerosol optical thickness observed from operational satellite AVHRR instrument

Abstract. The main purpose of the present paper is to derive and discuss linear long-term trends of Aerosol Optical Thickness (AOT) at 443 and 555 nm over regions in Europe and South China. These areas are densely populated and highly polluted. The study uses the Bremen AErosol Retrieval (BAER) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data for AOT retrievals in the specified regions from October 1997 to May 2008. In order to validate the individually retrieved AOTs and the corresponding trends, AErosol RObotic NETwork (AERONET) level 2.0 data have been used. The retrieved AOTs were in good agreement with those of AERONET (0.79 ≤ R ≤ 0.88, 0.08 ≤ RMSD ≤ 0.13). The contamination of BAER aerosol retrievals and/or AERONET observations by thin clouds can significantly degrade the AOT and lead to statistically non-representative monthly-means, especially during cloudy seasons. Therefore an inter-correction method has been developed and applied. The "corrected" trends for both BAER SeaWiFS and AERONET AOT were similar having an average of relative error ~25.19 %. In general terms, negative trends (decrease of aerosol loading) were mainly observed over European regions, with magnitudes up to −0.00453 (−1.93 %) and −0.00484 (−2.35 %) per year at 443 and 555 nm, respectively. In contrast, the trend in Pearl River Delta was positive, most likely attributed to rapid urbanization and industrialization. The magnitudes of AOT increased by +0.00761 (+1.24 %) and +0.00625 (+1.15 %) per year respectively at 443 and 555 nm.

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Long-term changes in the aerosol optical thickness in moscow and correction under strong atmospheric turbidity

Izvestiya Atmospheric and Oceanic Physics ◽

10.1134/s0001433816010035 ◽

2016 ◽

Vol 52 (2) ◽

pp. 188-195 ◽

Cited By ~ 4

Author(s):

E. V. Gorbarenko ◽

A. N. Rublev

Keyword(s):

Optical Thickness ◽

Aerosol Optical Thickness ◽

Atmospheric Turbidity ◽

Long Term Changes

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Trend analysis of the Aerosol Optical Thickness and Ångström Exponent derived from the global AERONET spectral observations

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-4-5325-2011 ◽

2011 ◽

Vol 4 (4) ◽

pp. 5325-5388 ◽

Cited By ~ 7

Author(s):

J. Yoon ◽

W. von Hoyningen-Huene ◽

A. A. Kokhanovsky ◽

M. Vountas ◽

J. P. Burrows

Keyword(s):

Trend Analysis ◽

Optical Thickness ◽

Weighted Least Squares ◽

Temporal Trends ◽

Aerosol Optical Thickness ◽

Anthropogenic Aerosols ◽

Angstrom Exponent ◽

Ångström Exponent ◽

Ångstrom Exponent

Abstract. Regular aerosol observations based on well-calibrated instruments have led to a better understanding of the aerosol radiative budget on Earth. In recent years, these instruments have played an important role in the determination of the increase of anthropogenic aerosols by means of long-term studies. Only few investigations regarding long-term trends of aerosol optical characteristics (e.g. Aerosol Optical Thickness (AOT) and Ångström Exponent (ÅE)) have been derived from ground-based observations. This paper aims to derive and discuss linear trends of AOT (440, 675, 870, and 1020 nm) and ÅE (440–870 nm) using AErosol RObotic NETwork (AERONET) spectral observations. Additionally, temporal trends of Coarse- and Fine-mode dominant AOTs (CAOT and FAOT) have been estimated by applying an aerosol classification based on accurate ÅE and Ångström Exponent Difference (ÅED). In order to take into account the fact that cloud disturbance is having a significant influence on the trend analysis of aerosols, we introduce a weighted least squares regression depending on two weights: (1) monthly standard deviation and (2) Number of Observations (NO) per month. Temporal increase of FAOTs prevails over regions dominated by emerging economy or slash-burn agriculture in East Asia and South Africa. On the other hand, insignificant or negative trends for FAOTs are detected over Western Europe and North America. Over desert regions, both increase and decrease of CAOTs are observed depending on meteorological conditions.

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Study of long-term trend in aerosol optical thickness observed from operational AVHRR satellite instrument

Journal of Geophysical Research Atmospheres ◽

10.1029/2007jd009061 ◽

2008 ◽

Vol 113 (D7) ◽

Cited By ~ 92

Author(s):

Tom X.-P. Zhao ◽

Istvan Laszlo ◽

Wei Guo ◽

Andrew Heidinger ◽

Changyong Cao ◽

...

Keyword(s):

Optical Thickness ◽

Aerosol Optical Thickness ◽

Term Trend ◽

Long Term Trend

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Analysis of linear long-term trend of aerosol optical thickness derived from SeaWiFS using BAER over Europe and South China

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-12149-2011 ◽

2011 ◽

Vol 11 (23) ◽

pp. 12149-12167 ◽

Cited By ~ 42

Author(s):

J. Yoon ◽

W. von Hoyningen-Huene ◽

M. Vountas ◽

J. P. Burrows

Keyword(s):

South China ◽

Optical Thickness ◽

Correction Method ◽

Relative Difference ◽

Aerosol Optical Thickness ◽

Wide Field ◽

Rapid Urbanization ◽

Research Areas ◽

General Terms

Abstract. The main purposes of the present paper are not only to investigate linear long-term trends of Aerosol Optical Thickness (AOT) at 443 and 555 nm over regions in Europe and South China, but also to show the uncertainty caused by cloud disturbance in the trend analysis of cloud-free aerosol. These research areas are the densely urbanised and often highly polluted regions. The study uses the Bremen AErosol Retrieval (BAER) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data for AOT retrievals in the specified regions from October 1997 to May 2008. In order to validate the individually retrieved AOTs and the corresponding trends, AErosol RObotic NETwork (AERONET) level 2.0 data have been used. The retrieved AOTs were in good agreement with those of AERONET (0.79 ≤ R ≤ 0.88, 0.08 ≤ RMSD ≤ 0.13). The contamination of the aerosol retrievals and/or AERONET observations by thin clouds can significantly degrade the AOT and lead to statistically non-representative monthly-means, especially during cloudy seasons. Therefore an inter-correction method has been developed and applied. The "corrected" trends for both BAER SeaWiFS and AERONET AOT were similar and showed in average a relative difference of ∼25.19%. In general terms, negative trends (decrease of aerosol loading) were mainly observed over European regions, with magnitudes up to −0.00453 and −0.00484 yr−1 at 443 and 555 nm, respectively. In contrast, the trend in Pearl River Delta was positive, most likely attributed to rapid urbanization and industrialization. The magnitudes of AOT increased by +0.00761 and +0.00625 yr−1 respectively at 443 and 555 nm.

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Long-term variability of aerosol optical thickness in Eastern Europe over 2001–2014 according to the measurements at the Moscow MSU MO AERONET site with additional cloud and NO<sub>2</sub> correction

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-7843-2015 ◽

2015 ◽

Vol 8 (7) ◽

pp. 7843-7878

Author(s):

N. Y. Chubarova ◽

A. A. Poliukhov ◽

I. D. Gorlova

Keyword(s):

Optical Thickness ◽

Aerosol Optical Thickness ◽

Quality Data ◽

Emission Rates ◽

State University ◽

Data Control ◽

Uv Irradiance ◽

Meteorological Observatory ◽

Moscow State University

Abstract. The aerosol properties of the atmosphere were obtained within the framework of the AERONET program at the Moscow State University Meteorological Observatory (Moscow MSU MO) over 2001–2014 period. The quality data control has revealed the necessity of their additional cloud and NO2 correction. The application of cloud correction according to hourly visual cloud observations provides a decrease in average aerosol optical thickness (AOT) at 500 nm of up to 0.03 compared with the standard dataset. We also show that the additional NO2 correction of the AERONET data is needed in large megalopolis, like Moscow, with 12 million residents and the NOx emission rates of about 100 kt yr−1. According to the developed method we estimated monthly mean NO2 content, which provides an additional decrease of 0.01 for AOT at 340 nm, and of about 0.015 – for AOT at 380 and 440 nm. The ratios of NO2 optical thickness to AOT at 380 and 440 nm are about 5–6 % in summer and reach 15–20 % in winter when both factors have similar effects on UV irradiance. Seasonal cycle of AOT at 500 nm is characterized by a noticeable summer and spring maxima, and minimum in winter conditions, changing from 0.08 in December and January up to 0.3 in August. The application of the additional cloud correction removes a local AOT maximum in February, and lowered the December artificial high AOT values. The pronounced negative AOT trends of about −1–5 % yr−1 have been obtained for most months, which could be attributed to the negative trends in emissions (E) of different aerosol precursors of about 116 Gg yr−2 in ESOx, 78 Gg yr−2 in ENMVOC, and 272 Gg yr−2 in ECO over European territory of Russia. No influence of natural factors on temporal AOT variations has been revealed.

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The Impact of COVID-19 Lockdowns on Satellite-Observed Aerosol Optical Thickness over the Surrounding Coastal Oceanic Areas of Megacities in the Coastal Zone

Geographies ◽

10.3390/geographies1030021 ◽

2021 ◽

Vol 1 (3) ◽

pp. 381-397

Author(s):

Kai Wang ◽

Xuepeng Zhao

Keyword(s):

Optical Thickness ◽

Satellite Observation ◽

Dust Storms ◽

Aerosol Optical Thickness ◽

Climate Data ◽

Aerosol Emission ◽

The Impact ◽

Climate Data Record ◽

Global Oceans

Nearly 40 years of aerosol optical thickness (AOT) climate data record (CDR) derived from NOAA operational satellite Advanced Very High Resolution Radiometer (AVHRR) observation over the global oceans is used to study the AOT changes due to the COVID-19 lockdown over the surrounding coastal oceanic areas of 18 megacities in the coast zone (MCCZ). The AOT difference between the annual mean AOT values of 2020 with COVID-19 lockdown and 2019 without the lockdown along with the 2020 AOT annual anomaly are used to effectively identify the AOT changes that are a result of the lockdown. We found that for most of the 18 MCCZ, the COVID-19 lockdowns implemented to contain the spread of the coronavirus resulted in a decrease between 1% and 30% in AOT due to reduced anthropogenic emissions associated with the lockdowns. However, the AOT long-term trend and other aerosol interannual variations due to favorable or unfavorable meteorological conditions may mask AOT changes due to the lockdown effect in some MCCZ. Different seasonal variations of aerosol amount in 2020 relative to 2019 due to other natural aerosol emission sources not influenced by the lockdown, such as dust storms and natural biomass burning and smoke, may also conceal a limited reduction in the annual mean AOT due to the lockdown in MCCZ with relatively loose lockdown. This study indicates that the use of long-term satellite observation is helpful for studying and monitoring the aerosol changes due to the emission reduction associated with the COVID-19 lockdown in the surrounding coastal oceanic areas of MCCZ, which will benefit the future development of the mitigation strategy for air pollution and emissions in megacities.

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