scholarly journals Annual Changes of Aerosol Optical Depth and Ångström Exponent over Spitsbergen

2015 ◽  
pp. 23-36 ◽  
Author(s):  
P. Pakszys ◽  
T. Zielinski ◽  
K. Markowicz ◽  
T. Petelski ◽  
P. Makuch ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Annual Changes ◽  
Ångstrom Exponent

scholarly journals Retrieval of aerosol single-scattering albedo and polarized phase function from polarized sun-photometer measurements for Zanjan's atmosphere

2013 ◽  
Vol 6 (10) ◽  
pp. 2659-2669 ◽  
Author(s):  
A. Bayat ◽  
H. R. Khalesifard ◽  
A. Masoumi
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Phase Function ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Sun Photometer ◽  
Ångstrom Exponent

Abstract. The polarized phase function of atmospheric aerosols has been investigated for the atmosphere of Zanjan, a city in northwest Iran. To do this, aerosol optical depth, Ångström exponent, single-scattering albedo, and polarized phase function have been retrieved from the measurements of a Cimel CE 318-2 polarized sun-photometer from February 2010 to December 2012. The results show that the maximum value of aerosol polarized phase function as well as the polarized phase function retrieved for a specific scattering angle (i.e., 60°) are strongly correlated (R = 0.95 and 0.95, respectively) with the Ångström exponent. The latter has a meaningful variation with respect to the changes in the complex refractive index of the atmospheric aerosols. Furthermore the polarized phase function shows a moderate negative correlation with respect to the atmospheric aerosol optical depth and single-scattering albedo (R = −0.76 and −0.33, respectively). Therefore the polarized phase function can be regarded as a key parameter to characterize the atmospheric particles of the region – a populated city in the semi-arid area and surrounded by some dust sources of the Earth's dust belt.

scholarly journals Aerosol optical properties at Lampedusa (Central Mediterranean). 1. Influence of transport and identification of different aerosol types

2006 ◽  
Vol 6 (3) ◽  
pp. 697-713 ◽  
Author(s):  
G. Pace ◽  
A. di Sarra ◽  
D. Meloni ◽  
S. Piacentino ◽  
P. Chamard
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Central Mediterranean ◽  
Desert Dust ◽  
Central Eastern Europe ◽  
Angstrom Exponent ◽  
The North ◽  
Ångström Exponent ◽  
Summer Maximum ◽  
Ångstrom Exponent

Abstract. Aerosol optical depth and Ångström exponent were obtained from multi filter rotating shadowband radiometer (MFRSR) observations carried out at the island of Lampedusa, in the Central Mediterranean, in the period July 2001–September 2003. The average aerosol optical depth at 495.7 nm, τ, is 0.24±0.14; the average Ångström exponent, α, is 0.86±0.63. The observed values of τ range from 0.03 to 1.13, and the values of α vary from −0.32 to 2.05, indicating a large variability in aerosol content and size. In cloud-free conditions, 36% of the airmasses come from Africa, 25% from Central-Eastern Europe, and 19% from Western France, Spain and the North Atlantic. In summer, 42% of the airmasses is of African origin. In almost all cases African aerosols display high values of τ and low values of α, typical of Saharan dust (average values of τ and α are 0.36 and 0.42, respectively). Particles originating from Central-Eastern Europe show relatively large average values of τ and α (0.23 and 1.5, respectively), while particles from Western France, Spain and the North Atlantic show the lowest average values of τ (0.15), and relatively small values of α (0.92). Intermediate values of α are often connected with relatively fast changes of the airmass originating sector, suggesting the contemporary presence of different types of particles in the air column. Clean marine conditions are rare at Lampedusa, and are generally associated with subsidence of the airmasses reaching the island. Average values of τ and α for clean marine conditions are 0.11 and 0.86, respectively. The largest values of α (about 2) were observed in August 2003, when large scale forest fires in Southern Europe produced consistent amounts of fine combustion particles, that were transported to the Central Mediterranean by a persistent high pressure system over Central Europe. Smoke particles in some cases mix with desert dust, producing intermediate values of α. The seasonal distribution of the meteorological patterns over the Mediterranean, the efficiency of the aerosol production mechanisms, and the variability of the particles' residence time produce a distinct seasonal cycle of aerosol optical depths and Ångström exponent values. Particles originating from all sectors show a summer maximum in aerosol optical depth. The summer increase in optical depth for European aerosols is linked with an increment in the values of α, that indicates an enhancement in the number of fine particles. The summer maximum of τ for African particles is associated with a weak reduction in the Ångström exponent, suggesting an increase in the total number of particles and a relatively more intense transport of large particles. The observations were classified according to the aerosol optical properties, and two main classes have been identified: desert dust and biomass burning/urban-industrial aerosols. Values of τ and α averaged over the whole observing period are 0.37 and 0.15 for desert dust, and 0.27 and 1.77 for urban-industrial/biomass burning aerosols.

scholarly journals The regime of Aerosol Optical Depth and Ångström exponent over Central and South Asia

2019 ◽  
Vol 99 ◽  
pp. 01003
Author(s):  
Athina Avgousta Floutsi ◽  
Marios Bruno Korras Carraca ◽  
Christos Matsoukas ◽  
Nikos Hatzianastassiou ◽  
George Biskos
Keyword(s):  
South Asia ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Dust Particles ◽  
Desert Dust ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Dust Load ◽  
Ångstrom Exponent

Central and South Asia are regions of particular interest for studying atmospheric aerosols, being among the largest sources of desert dust aerosols globally. In this study we use the newest collection (C061) of MODIS - Aqua aerosol optical depth (AOD) at 550 nm and Ångström exponent (a) at 412/470 nm over the 15-year period between 2002 and 2017, providing the longest analyzed dataset for this region. According to our results, during spring and summer, high aerosol load (AOD up to 1.2) consisting of coarse desert dust particles, as indicated by a values as low as 0.15, is observed over the Taklamakan, Thar and Registan deserts and the region between the Aral and Caspian seas. The dust load is much lower during winter and autumn (lower AOD and higher a values compared to the other seasons). The interannual variation of AOD and a suggests that the dust load exhibits large decreasing trends (AOD slopes down to -0.22, a slopes up to 0.47 decade-1) over the Thar desert and large increasing trends between the Aral and Caspian seas (AOD and a slopes up to 0.23 decade-1 and down to -0.61 decade-1, respectively.) The AOD data are evaluated against AERONET surface-based measurements. Generally, MODIS and AERONET data are in good agreement with a correlation coefficient (R) equal to 0.835.

scholarly journals Studying Air Pollutants Origin and Associated Meteorological Parameters over Seoul from 2000 to 2009

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Sunmin Park ◽  
Hesham El-Askary ◽  
Ismail Sabbah ◽  
Hanbin Kwak ◽  
Anup K. Prasad ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Air Pollutants ◽  
Winter Season ◽  
Summer Season ◽  
Seasonal Effect ◽  
Temporal Characteristics ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

We investigate the temporal characteristics of major air pollutants collected from 44 air quality stations over the city of Seoul, Korea, namely, nitrogen dioxide, carbon monoxide, particular matter at 10 microns, and sulfur dioxide (SO2) between 2000 and 2009. The corresponding satellite datasets, namely, aerosol optical depth (AODsat), Ångström exponent, and fine mode fraction, collected from moderate resolution imaging spectroradiometer (MODIS) as well as the Aeronet ground aerosol optical depth (AODaeronet), have been analyzed. Pollutants’ seasonal effect has been inferred from the precipitation and temperature. The four pollutants under study show varying temporal characteristics with different annual mean concentration patterns. The monthly mean of mentioned pollutants all show similar low concentrations during the summer season and high concentrations during the winter season. We found that pollution is strongly linked to temperature and precipitation variability, especially during the fall season. Satellite data analysis provides information on the pollutants origin whether of natural or anthropogenic type. Our results indicate that the anthropogenic aerosol is dominant in the summer season even though the concentration was lower than the other seasons. AODaeronetand Ångström exponent indicated high positive and negative correlation coefficients with PM10, 0.60, and −0.45, respectively. Both small and large sizes of aerosols existed in 2007; however coarse size of aerosols was the primary component in 2002.

scholarly journals Extreme Saharan dust event over the southern Iberian Peninsula in september 2007: active and passive remote sensing from surface and satellite

2009 ◽  
Vol 9 (4) ◽  
pp. 15673-15723
Author(s):  
J. L. Guerrero-Rascado ◽  
F. J. Olmo ◽  
I. Avilés-Rodríguez ◽  
F. Navas-Guzmán ◽  
D. Pérez-Ramírez ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Iberian Peninsula ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Saharan Dust ◽  
Dust Event ◽  
Passive Remote Sensing ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Abstract. This study investigates aerosol optical properties during the extreme Saharan dust event detected from 3 to 7 September 2007 over Granada, southern Iberian Peninsula, with both active and passive remote sensing instrumentation from surface and satellite. The intensity of the event was visualized on the aerosol optical depth series obtained by the sun-photometer Cimel CE 318-4 operated at Granada in the framework of AERONET from August 2004 until December 2008 (level 2 data). A combination of large aerosol optical depth (0.86–1.50) at 500 nm, and reduced Angström exponent (0.1–0.25) in the range 440–870 nm, was detected on 6 September during daytime. This Saharan dust event also affected other Iberian Peninsula stations included in AERONET (El Arenosillo and Évora stations). During the most intense stage, on 6 September, maximum aerosol backscatter values were a factor of 8 higher than other maxima during this Saharan dust event. Values up to 1.5×10−2 km−1 sr−1 at 355 and 532 nm were detected in the layer with the greatest aerosol load between 3–4 km a.s.l., although aerosol particles were also detected up to 5.5 km a.s.l. In this stage of the event, dust particles at these altitudes showed a backscatter-related Angström exponent between −0.44 and 0.53 for the two spectral intervals considered. The results from different measurements (active/passive and ground-based/satellite) reveal the importance of performing multi-instrumental measurements to properly characterize the contribution of different aerosol types from different sources during extreme events.

Inferring Angstrom Exponent and Aerosol Optical Depth from AERONET

2014 ◽  
Vol 7 (3) ◽  
pp. 166-175 ◽  
Author(s):  
A.N. Alias ◽  
M.Z. MatJafri ◽  
H.S. Lim ◽  
N.M. Saleh ◽  
S.H. Chumiran ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

scholarly journals Improved Aerosol Optical Depth and Ångstrom Exponent Retrieval Over Land From MODIS Based on the Non-Lambertian Forward Model

2014 ◽  
Vol 11 (9) ◽  
pp. 1629-1633 ◽  
Author(s):  
Leiku Yang ◽  
Yong Xue ◽  
Jie Guang ◽  
Hassan Kazemian ◽  
Jiahua Zhang ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Forward Model ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Aerosol optical depth and Ångström exponent climatology at El Arenosillo AERONET site (Huelva, Spain)

10.1002/qj.54 ◽  
2007 ◽  
Vol 133 (624) ◽  
pp. 795-807 ◽  
Author(s):  
C. Toledano ◽  
V. E. Cachorro ◽  
A. Berjon ◽  
A. M. de Frutos ◽  
M. Sorribas ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Retrievals of Aerosol Optical Depth and Angstrom Exponent for Identification of Aerosols at Kuching, Sarawak

2012 ◽  
Vol 518-523 ◽  
pp. 5734-5737 ◽  
Author(s):  
Khairunnisa Abd Jalal ◽  
Arnis Asmat ◽  
Noordin Ahmad
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiation Budget ◽  
Dust Particles ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Two Parameters ◽  
Log Linear ◽  
Ångstrom Exponent ◽  
Aerosol Properties

Anthropogenic and natural aerosols are important atmospheric constituents that significantly contribute to the Earth’s radiation budget but remain uncertainties due to the poor understanding of aerosol properties and its direct effects on scattering and absoprtion of solar radiation and the ability of aerosols to stay in atmosphere for a very short time. Different types of aerosols, representing biomass burning, urban or continental aerosols, maritime aerosols and dust particles will give different characterization and classification of aerosol properties. The data used in this study was obtained from Aerosol Robotic Network (AERONET).Two parameters were used for aerosol analysis which are Aerosol Optical Depth (AOD) at four wavelengths (440, 500, 675 and 870nm) and Angstrom exponent (α) derived from a multispectral log linear.

Sign in / Sign up

Export Citation Format

Share Document