Retrieval and Validation of Long-Term Aerosol Optical Depth from AVHRR Over China Mainland

2021 ◽  
Author(s):  
Chunlin Jin ◽  
Yong Xue ◽  
Xingxing Jiang ◽  
Rui Bai ◽  
Yuxin Sun ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
China Mainland

scholarly journals Aerosol optical depth retrievals at the Izaña Atmospheric Observatory from 1941 to 2013 by using artificial neural networks

2016 ◽  
Vol 9 (1) ◽  
pp. 53-62 ◽  
Author(s):  
R. D. García ◽  
O. E. García ◽  
E. Cuevas ◽  
V. E. Cachorro ◽  
A. Barreto ◽  
...  
Keyword(s):  
Neural Networks ◽  
Time Series ◽  
Artificial Neural Networks ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Mineral Dust ◽  
Dust Particles ◽  
Filter Radiometer ◽  
Artificial Neural

Abstract. This paper presents the reconstruction of a 73-year time series of the aerosol optical depth (AOD) at 500 nm at the subtropical high-mountain Izaña Atmospheric Observatory (IZO) located in Tenerife (Canary Islands, Spain). For this purpose, we have combined AOD estimates from artificial neural networks (ANNs) from 1941 to 2001 and AOD measurements directly obtained with a Precision Filter Radiometer (PFR) between 2003 and 2013. The analysis is limited to summer months (July–August–September), when the largest aerosol load is observed at IZO (Saharan mineral dust particles). The ANN AOD time series has been comprehensively validated against coincident AOD measurements performed with a solar spectrometer Mark-I (1984–2009) and AERONET (AErosol RObotic NETwork) CIMEL photometers (2004–2009) at IZO, obtaining a rather good agreement on a daily basis: Pearson coefficient, R, of 0.97 between AERONET and ANN AOD, and 0.93 between Mark-I and ANN AOD estimates. In addition, we have analysed the long-term consistency between ANN AOD time series and long-term meteorological records identifying Saharan mineral dust events at IZO (synoptical observations and local wind records). Both analyses provide consistent results, with correlations  >  85 %. Therefore, we can conclude that the reconstructed AOD time series captures well the AOD variations and dust-laden Saharan air mass outbreaks on short-term and long-term timescales and, thus, it is suitable to be used in climate analysis.

scholarly journals Nine years of UV aerosol optical depth measurements at Thessaloniki, Greece

2007 ◽  
Vol 7 (8) ◽  
pp. 2091-2101 ◽  
Author(s):  
S. Kazadzis ◽  
A. Bais ◽  
V. Amiridis ◽  
D. Balis ◽  
C. Meleti ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Back Trajectories ◽  
Air Masses ◽  
North Eastern ◽  
Range Transport ◽  
Air Quality Monitoring Stations ◽  
Pm 10 ◽  
The City

Abstract. Spectral measurements of the aerosol optical depth (AOD) and the Ångström coefficient were conducted at Thessaloniki, Greece (40.5° N, 22.9° E) between January 1997 and December 2005 with a Brewer MKIII double-monochromator spectroradiometer. The dataset was compared with collocated measurements of a second spectroradiometer (Brewer MKII) and a CIMEL sun-photometer, showing correlations of 0.93 and 0.98, respectively. A seasonal variation of the AOD was observed at Thessaloniki, with AOD values at 340 nm of 0.52 and 0.28 for August and December respectively. Back trajectories of air masses for up to 4 days were used to assess the influence of long-range transport from various regions to the aerosol load over Thessaloniki. It is shown that part of the observed seasonality can be attributed to air masses with high AOD originating from North-Eastern and Eastern directions during summertime. The analysis of the long-term record (9 years) of AOD showed a downward tendency. A similar decreasing tendency was found in the record of the PM$_{10}$ aerosol measurements, which are conducted near the surface at 4 air-quality monitoring stations in the area of the city of Thessaloniki.

Long-term (1995–2018) aerosol optical depth derived using ground based AERONET and SKYNET measurements from aerosol aged-background sites

2019 ◽  
Vol 10 (2) ◽  
pp. 608-620 ◽  
Author(s):  
Shantikumar S. Ningombam ◽  
E.J.L. Larson ◽  
U.C. Dumka ◽  
Victor Estellés ◽  
M. Campanelli ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth

scholarly journals Aerosol optical depth retrievals in central Amazonia from a multi-filter rotating shadow-band radiometer calibrated on-site

2019 ◽  
Vol 12 (2) ◽  
pp. 921-934
Author(s):  
Nilton E. Rosário ◽  
Thamara Sauini ◽  
Theotonio Pauliquevis ◽  
Henrique M. J. Barbosa ◽  
Marcia A. Yamasoe ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Spectral Response ◽  
Monitoring Site ◽  
Direct Normal Irradiance ◽  
Central Amazonia ◽  
Long Term Monitoring ◽  
Term Monitoring ◽  
Band Radiometer

Abstract. Extraterrestrial spectral response calibration of a multi-filter rotating shadow band radiometer (MFRSR) under pristine Amazonian Forest atmosphere conditions was performed using the Langley plot method. The MFRSR is installed in central Amazonia as part of a long-term monitoring site, which was used in the context of the GoAmazon2014/5 experiment. It has been operating continuously since 2011 without regular extraterrestrial calibration, preventing its application to accurate monitoring of aerosol particles. Once calibrated, the MFRSR measurements were applied to retrieve aerosol particle columnar optical properties, specifically aerosol optical depth (AODλ) and Ångström exponent (AE), which were evaluated against retrievals from a collocated Cimel Sun photometer belonging to the AErosol RObotic NETwork (AERONET). Results obtained revealed that pristine Amazonian conditions are able to provide MFRSR extraterrestrial spectral response with relative uncertainty lower than 1.0 % in visible channels. The worst estimate (air mass =1) for absolute uncertainty in AODλ retrieval varied from ≈0.02 to ≈0.03, depending on the assumption regarding uncertainty for MFRSR direct normal irradiance measured at the surface. The obtained root mean square error (RMSE ≈0.025) from the evaluation of MFRSR retrievals against AERONET AODλ was, in general, lower than estimated MFRSR AODλ uncertainty, and close to the uncertainty of AERONET field Sun photometers (≈0.02).

Long‐Term Variability of Aerosol Optical Depth in the Tatra Mountain Region of Central Europe

2019 ◽  
Vol 124 (6) ◽  
pp. 3464-3475
Author(s):  
K. M. Markowicz ◽  
O. Zawadzka ◽  
M. Posyniak ◽  
J. Uscka‐Kowalkowska
Keyword(s):  
Aerosol Optical Depth ◽  
Central Europe ◽  
Optical Depth ◽  
Mountain Region

scholarly journals Evidence of a possible turning point in solar UV-B over Canada, Europe and Japan

2012 ◽  
Vol 12 (5) ◽  
pp. 2469-2477 ◽  
Author(s):  
C. S. Zerefos ◽  
K. Tourpali ◽  
K. Eleftheratos ◽  
S. Kazadzis ◽  
C. Meleti ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Total Ozone ◽  
Turning Point ◽  
Amplification Factor ◽  
Ground Level ◽  
Cloud Fraction ◽  
Spectral Irradiance ◽  
Solar Uv

Abstract. This study examines the long-term variability of UV solar irradiances at 305 nm and 325 nm over selected sites in Canada, Europe and Japan. Site selection was restricted to the availability of the most complete UV spectroradiometric datasets during the period 1990–2011. The analysis includes the long-term variability of total ozone, aerosol optical depth and cloud fraction at the sites studied. The results, based on observations and modeling, suggest that over Canada, Europe and Japan the period under study can be divided into three sub-periods of scientific merit: the first period (1991–1994) is the period perturbed by the Pinatubo volcanic eruption, during which excess volcanic aerosol has enhanced the "conventional" amplification factor of UV-B at ground level by an additional factor that depends on solar elevation. The increase of the UV-B amplification factor is the result of enhanced scattering processes caused by the injection of huge amounts of volcanic aerosols during the perturbed period. The second period (1995–2006) is characterized by a 0.14% yr−1 increase in total ozone and an increasing trend in spectral irradiance by 0.94% yr−1 at 305 nm and 0.88% yr−1 at 325 nm. That paradox was caused by the significant decline of the aerosol optical depth by more than 1% yr−1 (the "brightening" effect) and the absence of any statistically significant trend in the cloud fraction. The third period (2007–2011) shows statistically significant evidence of a slowdown or even a turning point in the previously reported upward UV-B trends over Canada, Europe and Japan.

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