Aerosol optical, microphysical and radiative properties at regional
background insular sites in the western Mediterranean

Abstract. In the framework of the ChArMEx (the Chemistry-Aerosol Mediterranean Experiment; http://charmex.lsce.ipsl.fr/) program, the seasonal variability of the aerosol optical, microphysical and radiative properties derived from AERONET (Aerosol Robotic Network; http://aeronet.gsfc.nasa.gov/) is examined in two regional background insular sites in the western Mediterranean Basin: Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). A third site, Alborán (Alborán Island, Spain), with only a few months of data is considered for examining possible northeast–southwest (NE–SW) gradients of the aforementioned aerosol properties. The AERONET dataset is exclusively composed of level 2.0 inversion products available during the 5-year period 2011–2015. AERONET solar radiative fluxes are compared with ground- and satellite-based flux measurements. To the best of our knowledge this is the first time that AERONET fluxes are compared with measurements at the top of the atmosphere. Strong events (with an aerosol optical depth at 440 nm greater than 0.4) of long-range transport aerosols, one of the main drivers of the observed annual cycles and NE–SW gradients, are (1) mineral dust outbreaks predominant in spring and summer in the north and in summer in the south and (2) European pollution episodes predominant in autumn. A NE–SW gradient exists in the western Mediterranean Basin for the aerosol optical depth and especially its coarse-mode fraction, which all together produces a similar gradient for the aerosol direct radiative forcing. The aerosol fine mode is rather homogeneously distributed. Absorption properties are quite variable because of the many and different sources of anthropogenic particles in and around the western Mediterranean Basin: North African and European urban areas, the Iberian and Italian peninsulas, most forest fires and ship emissions. As a result, the aerosol direct forcing efficiency, more dependent to absorption than the absolute forcing, has no marked gradient.

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Aerosol optical, microphysical and radiative properties at three regional background insular sites in the western Mediterranean Basin

10.5194/acp-2015-823 ◽

2016 ◽

Cited By ~ 2

Author(s):

M. Sicard ◽

R. Barragan ◽

F. Dulac ◽

L. Alados-Arboledas ◽

M. Mallet

Keyword(s):

Radiative Forcing ◽

Mediterranean Basin ◽

Mineral Dust ◽

Western Mediterranean ◽

Radiative Properties ◽

Annual Cycles ◽

Regional Background ◽

Coarse Mode ◽

Western Mediterranean Basin ◽

Mode Volume

Abstract. In the framework of the ChArMEx (the Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/) program, the seasonal variability of the aerosol optical, microphysical and radiative properties is examined in two regional background insular sites in the western Mediterranean Basin (WMB): Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). A third site in Alborán (Alborán Island, Spain) with only a few months of data is considered for exploring the possible Northeast–Southwest (NE–SW) gradient of the aforementioned aerosol properties. The dataset is exclusively composed of AERONET (Aerosol Robotic Network; http://aeronet.gsfc.nasa.gov/) products during a four-year period (2011–2014). AERONET fluxes are validated with ground- and satellite-based flux measurements. To the best of our knowledge this is the first time that AERONET fluxes are validated at the top of the atmosphere. Products such as the aerosol optical depth (AOD), the fraction fine mode to total AOD, the particle size distribution, the sphericity, the radiative forcing and the radiative forcing efficiency show a clear annual cycle. The main drivers of the observed annual cycles are mineral dust outbreaks in summer and the transport of European continental aerosols in spring. A NE–SW gradient is observed on 6 parameters (3 extensive and 3 intensive) out of the 18 discussed in the paper. The NE–SW gradient of the AOD, the Ångström exponent, the coarse mode volume concentration, the sphericity and the radiative forcing at the surface are related to mineral dust outbreaks, while the NE–SW gradient of the coarse mode volume median radius is related to the decreasing influence of European continental aerosols along the NE–SW axis. The fact that two thirds of the parameters discussed in the paper do not present a NE–SW gradient is partly explained by two relevant findings: (1) a homogeneous spatial distribution of the fine particle loads over the three sites in spite of the distances between the sites and the differences in local sources, and (2) low values and the absence of spectral dependency of the absorption found in the southwesternmost site.

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Variability of Mediterranean aerosols properties at three regional background sites in the western Mediterranean Basin

10.1117/12.2068694 ◽

2014 ◽

Cited By ~ 1

Author(s):

Michaël Sicard ◽

Julien Totems ◽

Rubén Barragan ◽

François Dulac ◽

Marc Mallet ◽

...

Keyword(s):

Mediterranean Basin ◽

Western Mediterranean ◽

Regional Background ◽

Western Mediterranean Basin

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Sunphotometry of the 2006–2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory – Pyramid (5079 m a.s.l.)

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-1193-2010 ◽

2010 ◽

Vol 10 (1) ◽

pp. 1193-1220 ◽

Cited By ~ 11

Author(s):

G. P. Gobbi ◽

F. Angelini ◽

P. Bonasoni ◽

G. P. Verza ◽

A. Marinoni ◽

...

Keyword(s):

High Altitude ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Radiative Forcing ◽

Monsoon Season ◽

Good Reason ◽

Single Scattering ◽

Radiative Properties ◽

Mountain Range ◽

Monsoon Period

Abstract. In spite of being located at the heart of the highest mountain range in the world, the Himalayan Nepal Climate Observatory (5079 m a.s.l.) at the Ev-K2-CNR Pyramid is shown to be affected by the advection of pollution aerosols from the populated regions of southern Nepal and the Indo-Gangetic plains. Such an impact is observed along most of the period April 2006–March 2007 addressed here, with a minimum in the monsoon season. Backtrajectory-analysis indicates long-range transport episodes occurring in this period to originate mainly in the West Asian deserts. At this high altitude site, the measured aerosol optical depth is observed to be: 1) about one order of magnitude lower than the one measured at Gandhi College (60 m a.s.l.), in the Indo-Gangetic basin, and 2) maximum during the monsoon period, due to the presence of elevated (cirrus-like) particle layers. Assessment of the aerosol radiative forcing results to be hampered by the persistent presence of these high altitude particle layers, which impede a continuous measurement of both the aerosol optical depth and its radiative properties from sky radiance inversions. Even though the retrieved absorption coefficients of pollution aerosols was rather large (single scattering albedo of the order of 0.6–0.9 were observed in the month of April 2006), the corresponding low optical depths (~0.03 at 500 nm) are expected to limit the relevant radiative forcings. Still, the high specific forcing of this aerosol and its capability of altering snow surface albedo provide good reason for continuous monitoring.

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Aerosol distribution over the western Mediterranean basin during a Tramontane/Mistral event

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-11913-2006 ◽

2006 ◽

Vol 6 (6) ◽

pp. 11913-11956 ◽

Cited By ~ 2

Author(s):

T. Salameh ◽

P. Drobinski ◽

L. Menut ◽

B. Bessagnet ◽

C. Flamant ◽

...

Keyword(s):

Spatial Distribution ◽

Time Evolution ◽

Urban Areas ◽

Mediterranean Basin ◽

Western Mediterranean ◽

Airborne Lidar ◽

Radiation Budget ◽

Anthropogenic Aerosols ◽

Massif Central ◽

Western Mediterranean Basin

Abstract. This paper investigates experimentally and numerically the time evolution of the spatial distribution of aerosols over the Western Mediterranean basin during 24 March 1998 Mistral event documented during the FETCH experiment. Mistral and Tramontane are very frequent northerly winds (5–15 days per month) accelerated along the Rhône and Aude valley (France) that can transport natural and anthropogenic aerosols offshore as far as a few hundreds of kilometers which can in turn have an impact on the radiation budget over the Mediterranean Sea and on precipitation. The spatial distribution of aerosols was documented by means of the airborne lidar LEANDRE-2 and spaceborne radiometer SeaWIFS, and a validated mesoscale chemical simulation using the chemistry-transport model CHIMERE with an aerosol module, forced by the non-hydrostatic model MM5. This study shows that: (1) the Mistral contributes to the offshore exportation of a large amount of aerosols originally emitted over continental Europe (in particular ammonium nitrate in the particulate phase and sulfates) and along the shore from the industrialized and urban areas of Fos-Berre/Marseille. The Genoa surface low contributes to advect the aerosols along a cyclonic trajectory that skirts the North African coast and reaches Italy; (2) the aerosol concentration pattern is very unsteady as a result of the time evolution of the two winds (or Genoa cyclone position): The Tramontane wind prevails in the morning hours of 24 March, leaving room for the Mistral wind and an unusually strong Ligurian outflow in the afternoon. The wakes trailing downstream the Massif Central and the Alps prevent any horizontal diffusion of the aerosols and can, at times, contribute to aerosol stagnation.

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Sunphotometry of the 2006–2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory-Pyramid (5079 m a.s.l.)

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-11209-2010 ◽

2010 ◽

Vol 10 (22) ◽

pp. 11209-11221 ◽

Cited By ~ 31

Author(s):

G. P. Gobbi ◽

F. Angelini ◽

P. Bonasoni ◽

G. P. Verza ◽

A. Marinoni ◽

...

Keyword(s):

High Altitude ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Radiative Forcing ◽

Monsoon Season ◽

Single Scattering ◽

Radiative Properties ◽

Mountain Range ◽

Anthropogenic Aerosol ◽

Aerosol Radiative

Abstract. In spite of being located at the heart of the highest mountain range in the world, the Himalayan Nepal Climate Observatory (5079 m a.s.l.) at the Ev-K2-CNR Pyramid is shown to be affected by the advection of pollution aerosols from the populated regions of southern Nepal and the Indo-Gangetic plains. Such an impact is observed along most of the period April 2006–March 2007 addressed here, with a minimum in the monsoon season. Backtrajectory-analysis indicates long-range transport episodes occurring in this year to originate mainly in the west Asian deserts. At this high altitude site, the measured aerosol optical depth is observed to be about one order of magnitude lower than the one measured at Ghandi College (60 m a.s.l.), in the Indo-Gangetic basin. As for Ghandi College, and in agreement with the in situ ground observations at the Pyramid, the fine mode aerosol optical depth maximizes during winter and minimizes in the monsoon season. Conversely, total optical depth maximizes during the monsoon due to the occurrence of elevated, coarse particle layers. Possible origins of these particles are wind erosion from the surrounding peaks and hydrated/cloud-processed aerosols. Assessment of the aerosol radiative forcing is then expected to be hampered by the presence of these high altitude particle layers, which impede an effective, continuous measurement of anthropogenic aerosol radiative properties from sky radiance inversions and/or ground measurements alone. Even though the retrieved absorption coefficients of pollution aerosols were rather large (single scattering albedo of the order of 0.6–0.9 were observed in the month of April 2006), the corresponding low optical depths (~0.03 at 500 nm) are expected to limit the relevant radiative forcing. Still, the high specific forcing of this aerosol and its capability of altering snow surface albedo provide good reasons for continuous monitoring.

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Continental pollution in the Western Mediterranean Basin: vertical profiles of aerosol and trace gases measured over the sea during TRAQA 2012 and SAFMED 2013

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-8283-2015 ◽

2015 ◽

Vol 15 (6) ◽

pp. 8283-8328 ◽

Cited By ~ 1

Author(s):

C. Di Biagio ◽

L. Doppler ◽

C. Gaimoz ◽

N. Grand ◽

G. Ancellet ◽

...

Keyword(s):

Urban Areas ◽

Mediterranean Basin ◽

Trace Gases ◽

Western Mediterranean ◽

Saharan Dust ◽

Vertical Profiles ◽

Free Troposphere ◽

Aerosol Formation ◽

Western Mediterranean Basin ◽

Wide Range

Abstract. In this study we present airborne observations of aerosol and trace gases obtained over the sea in the Western Mediterranean Basin during the TRAQA (TRansport and Air QuAlity) and SAFMED (Secondary Aerosol Formation in the MEDiterranean) campaigns in summers 2012 and 2013. A total of 23 vertical profiles were measured up to 5000 m a.s.l. over an extended area (40–45° N latitude and 2° W–12° E longitude) including the Gulf of Genoa, Southern France, the Gulf of Lion, and the Spanish coast. TRAQA and SAFMED successfully measured a wide range of meteorological conditions which favoured the pollution export from different sources located around the basin. Also, several events of dust outflows were measured during the campaigns. Observations from the present study indicate that continental pollution largely affects the Western Mediterranean both close to coastal regions and in the open sea as far as ~250 km from the coastline. Aerosol layers not specifically linked with Saharan dust outflows are distributed ubiquitously which indicates quite elevated levels of background pollution throughout the Western Basin. The measured aerosol scattering coefficient varies between ~20 and 120 M m−1, while carbon monoxide (CO) and ozone (O3) mixing ratios are in the range of 60–170 and 30–85 ppbv, respectively. Pollution reaches 3000–4000 m in altitude and presents a very complex and highly stratified structure characterized by fresh and aged layers both in the boundary layer and in the free troposphere. Within pollution plumes the measured particle concentration in the Aitken (0.004–0.1 μm) and accumulation (0.1–1.0 μm) modes is between $\\sim 100$ and 5000–6000 s cm−3 (standard cm−3), which is comparable to the aerosol concentration measured in continental urban areas. Additionally, our measurements indicate the presence of highly concentrated Aitken layers (10 000–15 000 s cm−3) observed both close to the surface and in the free troposphere, possibly linked to the influence of new particle formation (NPF) episodes over the basin.

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Retrieval of Aerosol Optical Depth above Clouds from OMI Observations: Sensitivity Analysis and Case Studies

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-11-0130.1 ◽

2012 ◽

Vol 69 (3) ◽

pp. 1037-1053 ◽

Cited By ~ 91

Author(s):

Omar Torres ◽

Hiren Jethva ◽

P. K. Bhartia

Keyword(s):

Sensitivity Analysis ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Forest Fires ◽

Radiative Forcing ◽

Large Fraction ◽

Single Scattering ◽

Aerosol Layer ◽

Carbonaceous Particles ◽

True Value

Abstract A large fraction of the atmospheric aerosol load reaching the free troposphere is frequently located above low clouds. Most commonly observed aerosols above clouds are carbonaceous particles generally associated with biomass burning and boreal forest fires, and mineral aerosols originating in arid and semiarid regions and transported across large distances, often above clouds. Because these aerosols absorb solar radiation, their role in the radiative transfer balance of the earth–atmosphere system is especially important. The generally negative (cooling) top-of-the-atmosphere direct effect of absorbing aerosols may turn into warming when the light-absorbing particles are located above clouds. The actual effect depends on the aerosol load and the single scattering albedo, and on the geometric cloud fraction. In spite of its potential significance, the role of aerosols above clouds is not adequately accounted for in the assessment of aerosol radiative forcing effects due to the lack of measurements. This paper discusses the basis of a simple technique that uses near-UV observations to simultaneously derive the optical depth of both the aerosol layer and the underlying cloud for overcast conditions. The two-parameter retrieval method described here makes use of the UV aerosol index and reflectance measurements at 388 nm. A detailed sensitivity analysis indicates that the measured radiances depend mainly on the aerosol absorption exponent and aerosol–cloud separation. The technique was applied to above-cloud aerosol events over the southern Atlantic Ocean, yielding realistic results as indicated by indirect evaluation methods. An error analysis indicates that for typical overcast cloudy conditions and aerosol loads, the aerosol optical depth can be retrieved with an accuracy of approximately 54% whereas the cloud optical depth can be derived within 17% of the true value.

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A new multispectral photometer for monitoring aerosol microphysical, optical, and radiative properties

10.5194/amt-2021-365 ◽

2021 ◽

Author(s):

Yu Zheng ◽

Huizheng Che ◽

Yupeng Wang ◽

Xiangao Xia ◽

Xiuqing Hu ◽

...

Keyword(s):

Water Vapor ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Radiative Forcing ◽

Integrated Design ◽

Single Scattering ◽

Radiative Properties ◽

Mean Values ◽

Smart Control ◽

Fine Mode

Abstract. A new multispectral photometer, named CW193, was proposed in this study for monitoring aerosol microphysical, optical, and radiative properties. The instrument has a highly integrated design, smart control performance, and is composed of three parts (an optical head, a robotic drive platform, and a stents system). Because of its low maintenance requirements, this instrument is appropriate for the deployment in remote and unpopulated regions. Based on the synchronous measurements, the CW193 products was validated using reference data from the AERONET CE318 photometer. The results show that the raw digital counts from CW193 agree well the counts from AERONET (R2 > 0.97), with daily average triplets of around 1.2 % to 3.0 % for the ultraviolet band and less than 2.0 % for the visible and infrared bands. A good aerosol optical depth agreement (R > 0.99, 100 % within expected error) and root mean square error (RMSE) values ranging from 0.006 (for the 870 nm band) to 0.016 (for 440 nm the band) are obtained, with a relative mean bias (RMB) ranging from 0.922 to 1.112 and an aerosol optical depth bias within ±0.04. The maximum deviations for fine-mode particles varied from about 8.9 % to 77.6 %, whereas the variation for coarse-mode particles was about 13.1 % to 29.1 %. The deviation variations of the single scattering albedo were approximately 0.1–1.8 %, 0.6–1.9 %, 0.1–2.6 %, and 0.8–3.5 % for the 440 nm, 675 nm, 870 nm, and 1020 nm bands, respectively. For the aerosol direct radiative forcing, deviations of approximately 4.8–12.3 % was obtained at the Earth’s surface and 5.4–15.9 % for the top of the atmosphere. In addition, the water vapor retrievals showed a satisfactory accuracy, characterized by a high R value (~0.997), a small RMSE (~0.020), and good expected error distribution (100 % within expected error). The water vapor RMB was about 0.979 and the biases mostly varied within ±0.04, whereas the mean values were concentrated within ±0.02.

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