scholarly journals Three-dimensional evolution of Saharan dust transport towards Europe based on a 9-year EARLINET-optimized CALIPSO dataset

2017 ◽  
Vol 17 (9) ◽  
pp. 5893-5919 ◽  
Author(s):  
Eleni Marinou ◽  
Vassilis Amiridis ◽  
Ioannis Binietoglou ◽  
Athanasios Tsikerdekis ◽  
Stavros Solomos ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Three Dimensional ◽  
Satellite Observation ◽  
Saharan Dust ◽  
Winter Period ◽  
Dust Transport ◽  
The Balkans ◽  
Potential Applications ◽  
The Mediterranean ◽  
Dust Evolution

Abstract. In this study we use a new dust product developed using CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations and EARLINET (European Aerosol Research Lidar Network) measurements and methods to provide a 3-D multiyear analysis on the evolution of Saharan dust over North Africa and Europe. The product uses a CALIPSO L2 backscatter product corrected with a depolarization-based method to separate pure dust in external aerosol mixtures and a Saharan dust lidar ratio (LR) based on long-term EARLINET measurements to calculate the dust extinction profiles. The methodology is applied on a 9-year CALIPSO dataset (2007–2015) and the results are analyzed here to reveal for the first time the 3-D dust evolution and the seasonal patterns of dust over its transportation paths from the Sahara towards the Mediterranean and Continental Europe. During spring, the spatial distribution of dust shows a uniform pattern over the Sahara desert. The dust transport over the Mediterranean Sea results in mean dust optical depth (DOD) values up to 0.1. During summer, the dust activity is mostly shifted to the western part of the desert where mean DOD near the source is up to 0.6. Elevated dust plumes with mean extinction values between 10 and 75 Mm−1 are observed throughout the year at various heights between 2 and 6 km, extending up to latitudes of 40° N. Dust advection is identified even at latitudes of about 60° N, but this is due to rare events of episodic nature. Dust plumes of high DOD are also observed above the Balkans during the winter period and above northwest Europe during autumn at heights between 2 and 4 km, reaching mean extinction values up to 50 Mm−1. The dataset is considered unique with respect to its potential applications, including the evaluation of dust transport models and the estimation of cloud condensation nuclei (CCN) and ice nuclei (IN) concentration profiles. Finally, the product can be used to study dust dynamics during transportation, since it is capable of revealing even fine dynamical features such as the particle uplifting and deposition on European mountainous ridges such as the Alps and Carpathian Mountains.

scholarly journals 3D evolution of Saharan dust transport towards Europe based on a 9-year EARLINET-optimized CALIPSO dataset

2016 ◽  
Author(s):  
Eleni Marinou ◽  
Vassilis Amiridis ◽  
Ioannis Binietoglou ◽  
Stavros Solomos ◽  
Emannouil Proestakis ◽  
...  
Keyword(s):  
Saharan Dust ◽  
Winter Period ◽  
Dust Transport ◽  
North West ◽  
Ice Nuclei ◽  
Potential Applications ◽  
Lidar Ratio ◽  
The Mediterranean ◽  
Dust Evolution ◽  
First Time

Abstract. In this study we utilize a new dust product developed using CALIPSO observations and EARLINET measurements and methods to provide a 3D multiyear analysis on the evolution of Saharan dust over North Africa and Europe. The product utilizes CALIPSO L2 backscatter product corrected with a depolarization-based method to separate pure dust in external aerosol mixtures and an adjusted Saharan dust lidar ratio based on long-term EARLINET measurements. The methodology is applied on a nine-year CALIPSO dataset (2007–2015) and the results are analysed here to reveal for the first time the 3D dust evolution and the seasonal patterns of dust over its transportation paths from the Sahara towards the Mediterranean and Continental Europe. During spring, dust is uniformly distributed in the horizontal over the Sahara desert. The dust transport over the Mediterranean Sea results on mean Dust Optical Depth (DOD) values of 0.1. During summer, the dust activity is mostly shifted to the western part of the desert where mean DOD near the source is up to 0.6. Elevated dust plumes with mean extinction values between 10–75 Mm−1 are observed throughout the year at various heights between 2–6 km, extending up to latitudes of 40° N. Dust advection is identified even at latitudes of about 60° N, but this is due to rare events of episodic nature. Dust plumes of high DOD are also observed above Balkans during winter period and above North-West Europe during autumn at heights between 2–4 km, reaching mean extinction values up to 50 Mm−1. The dataset is considered unique with respect to its potential applications, including the evaluation of dust transport models and the estimation of cloud condensation and ice nuclei concentration profiles (CCN/IN). Finally, the product can be used to study dust dynamics during transportation, since it is capable of revealing even fine dynamical features such as the particle uplifting and deposition on European mountainous ridges such as Alps and Carpathian.

A climatology of dust episodes in the broader Mediterranean Basin using satellite MODIS C6.1 and OMI OMAERUV data

2020 ◽  
Author(s):  
Nikos Hatzianastassiou ◽  
Maria Gavrouzou ◽  
Antonis Gkikas ◽  
Nikos Mihalopoulos
Keyword(s):  
Optical Depth ◽  
Mediterranean Basin ◽  
Cloud Condensation Nuclei ◽  
Longwave Radiation ◽  
Threshold Value ◽  
Mean Value ◽  
Dust Transport ◽  
Cloud Properties ◽  
The Mediterranean ◽  
The Mediterranean Basin

<p>Aerosols, due to their interaction primary with the shortwave, but also with the longwave radiation, constitute a significant climate component, and at the same time an important, but still uncertain, factor of the contemporary climatic change. Apart from radiation, aerosols also interact with clouds, acting as Cloud Condensation Nuclei (CCN) and/or Ice Nuclei (IN), modifying the cloud optical and physical properties like cloud albedo, extent, lifetime or precipitation producing ability. Hence, it is also expected that high loads of specific aerosol types, such as desert dust, can induce even stronger effects on the above mentioned cloud properties.</p><p>More specifically, dust aerosols, which are inserted in the atmosphere mainly from the great world deserts, represent the major global aerosol component. These aerosols can remain suspended in the air and travel for several days, reaching areas far away from their sources. The Mediterranean Basin (MB), which is one of the most responsive regions to climate change, due to its location (nearby the Sahara desert in North Africa and the deserts of Middle East), is frequently affected from massive and extended dust transport. Because of the potentially significant role of these dust episodes, and their seasonal and inter-annual variability, they are worth to be studied and monitored through time.</p><p>In the present study, a modified version of a satellite algorithm, which is fully described by Gavrouzou et al. in another study of this conference, is used for the determination of strong and extreme dust episodes in the Mediterranean Basin over the period 2005-2018. The algorithm, using MODIS C6.1 spectral Aerosol Optical Depth (AOD) and OMI OMAERUV Aerosol Index (AI) as input data, ran on a daily and an 1°x1° pixel level basis and determined the occurrence and intensity of dust episodes whenever the AI is greater than 1 and the Angstrom Exponent (AE), which is calculated from spectral AOD data, is lower than 0.4. Any day is characterized as an episodic one when the dust optical depth (DOD) exceeds a computed threshold value (mean value plus two or four standard deviations for strong and extreme episodes, respectively) on at least 30 pixels of the study area. According to the algorithm results, 148 dust episode days (104 strong and 44 extreme) are found during the 2005-2018 period in the Mediterranean Basin. Most of the episodes occur in July (27 strong- and 3 extreme-episode days) and April (25 strong- and 6 extreme-episode days) while dust episodes are not detected at all in November and December. It is also found that in April, March and May take place the highest number of extreme MB episodes (23 out of the total 44 ones).</p>

A Case Study: The Indirect Aerosol Effects of Mineral Dust on Warm Clouds

2010 ◽  
Vol 67 (3) ◽  
pp. 805-816 ◽  
Author(s):  
R. Li ◽  
Q-L. Min ◽  
L. C. Harrison
Keyword(s):  
Cloud Condensation Nuclei ◽  
Statistical Significance ◽  
Radiant Energy ◽  
Energy System ◽  
Saharan Dust ◽  
Shortwave Radiation ◽  
Droplet Radius ◽  
Liquid Water Path ◽  
Precipitation Regime ◽  
Dust Transport

Abstract The indirect aerosol effect (Twomey effect) is studied during a Saharan dust-transport event that presented an unusually favorable combination of a dust-loading gradient across clouds with warm cloud-top temperatures. Standard retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E), and the Clouds and the Earth’s Radiant Energy System (CERES) provide cloud-top temperature (a surrogate for height), liquid water path (LWP), classification of precipitation regime, and radiation flux. The authors correlate a retrieved mean effective droplet radius (re) versus the number concentration of cloud condensation nuclei (NCCN), using the regressed slope d lnre/d lnNCCN as the estimator of the aerosol indirect effect (AIE). Results demonstrate statistically significant AIE for only some of the segregated cloud classes. For nonprecipitating clouds (the most direct test of Twomey effect), the estimated AIE is effectively −0.07 over all wider temperature bands and is statistically significant from 1.1 to 1.9 σ. Further classification by LWP strengthens both the AIE (for all LWP > 150 g m−2) to approximately −0.16, and substantially increases the statistical significance, to better than 5σ. Shortwave radiation forcing of dust aerosols is also estimated directly from satellite measurements. The direct shortwave (SW) radiation effect of Saharan dusts at solar zenith angle 21.6° is 53.48 ± 8.56 W m−2 per unit aerosol optical depth, with a correlation coefficient of 0.92. The indirect SW forcing of Saharan dust is 29.88 ± 2.42 W m−2 per unit AOD for clouds with LWP of 100 g m−2.

scholarly journals Patterns of Saharan dust transport over the Atlantic: winter vs. summer, based on CALIPSO first year data

2009 ◽  
Vol 9 (3) ◽  
pp. 13177-13198 ◽  
Author(s):  
Y. Ben-Ami ◽  
I. Koren ◽  
O. Altaratz
Keyword(s):  
Vertical Distribution ◽  
Vertical Structure ◽  
Marine Boundary Layer ◽  
Satellite Observation ◽  
Saharan Dust ◽  
First Year ◽  
Dust Transport ◽  
Stratiform Clouds ◽  
Shallow Clouds ◽  
Dust Effect

Abstract. One of the most important factors that determines the transported dust effect is its vertical distribution in the atmosphere. Until the launch of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), the vertical distribution was studied mostly by in-situ measurements and models. CALIPSO, as a part of the A-Train constellation has opened an opportunity to study the transported dust vertical structure in a large number of events (sufficient statistics). In this study the vertical structure of Saharan dust and stratiform clouds is analyzed over the Atlantic Ocean for the 2006–2007 winter (December–February) and the summer of 2006 (June–August). By using CALIPSO backscatter measurements over the dust route, we describe the differences in dust transport between the seasons. We show a bi-modal distribution of the average dust plumes height in both seasons (it is less clear in the winter). It suggests that a significant part of the dust is transported near and within the marine boundary layer and interacts with shallow clouds on both seasons.

scholarly journals Modelling Saharan dust transport into the Mediterranean basin with CMAQ

2013 ◽  
Vol 70 ◽  
pp. 337-350 ◽  
Author(s):  
David de la Paz ◽  
Michel Vedrenne ◽  
Rafael Borge ◽  
Julio Lumbreras ◽  
Juan Manuel de Andrés ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Saharan Dust ◽  
Dust Transport ◽  
The Mediterranean ◽  
The Mediterranean Basin

scholarly journals Interpreting elevated space-borne HCHO columns over the Mediterranean Sea using the OMI sensor

2011 ◽  
Vol 11 (24) ◽  
pp. 12787-12798 ◽  
Author(s):  
A. Sabolis ◽  
N. Meskhidze ◽  
G. Curci ◽  
P. I. Palmer ◽  
B. Gantt
Keyword(s):  
Mediterranean Sea ◽  
Hot Spot ◽  
Urban Atmosphere ◽  
Saharan Dust ◽  
Ozone Monitoring Instrument ◽  
Remotely Sensed Data ◽  
Vertical Column ◽  
Dust Transport ◽  
Wide Range ◽  
The Mediterranean

Abstract. Formaldehyde (HCHO) is an oxidation product of a wide range of volatile organic compounds (VOCs) and important atmospheric constituent found in both the polluted urban atmosphere and remote background sites. In this study, remotely sensed data of HCHO vertical column densities are analyzed over the Mediterranean Sea using the Ozone Monitoring Instrument (OMI). Data analysis indicates a marked seasonal cycle with a summer maximum and winter minimum confined to the marine environment during a three year period (2005–2007) examined. A possible retrieval artifact associated with Saharan dust transport over the region is explored by changing intensity of Saharan dust sources in GEOS-Chem following the recommendation of Generoso et al. (2008). Recalculated air mass factors (AMF), based on the new values of aerosol loadings, lead to a reduction of the summertime "hot spot" in OMI retrieval of HCHO vertical columns over the Mediterranean Sea; however, even after the correction, enhanced values are still present in this region. To explain these values, marine biogenic sources of VOCs are examined. Calculations indicate that emission of phytoplankton-produced isoprene is not likely to explain the enhanced HCHO vertical columns over the Mediterranean Sea. Model simulations in conjunction with measurements studies may be required to fully explore the complex mechanism of HCHO formation over the Mediterranean and its implications for the air quality in the region.

scholarly journals Remote sensing of aerosols over the oceans using MSG/SEVIRI imagery

2005 ◽  
Vol 23 (12) ◽  
pp. 3561-3568 ◽  
Author(s):  
F. Thieuleux ◽  
C. Moulin ◽  
F. M. Bréon ◽  
F. Maignan ◽  
J. Poitou ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Saharan Dust ◽  
Dust Transport ◽  
High Frequencies ◽  
Full Resolution ◽  
Fast Processing ◽  
Long Time ◽  
The Mediterranean ◽  
Good Agreement

Abstract. The SEVIRI instrument on board Meteosat Second Generation (MSG) offers new capabilities to monitor aerosol transport over the Atlantic and the Mediterranean at high temporal and spatial resolutions, in particular, Saharan dust from North Africa, biomass-burning aerosols from subtropical Africa and pollution from Europe. An inversion technique was developed to estimate both aerosol optical thickness and Angström coefficients from SEVIRI measurements at 0.63 and 0.81 µm. This method relies on an optimized set of aerosol models to ensure a fast processing of full-resolution MSG images and to allow the processing of long time series. SEVIRI images for slots 45, 49 and 53 (11:15, 12:15, 13:15 UT) were processed for June 2003. The retrieved optical thicknesses and Angström coefficients are in good agreement with AERONET in-situ measurements in the Atlantic and in the Mediterranean. Monthly mean maps of both parameters are compared to that obtained with the polar orbiting sensor POLDER for June 2003. There is a good consistency between the two monthly means in terms of optical thickness, but the Angström coefficients show significant differences in the Atlantic zone which is affected by dust transport. These differences may be explained by the lack of specific non-spherical dust models within the inversion. The preliminary results presented in this paper demonstrate, nevertheless, the potential of MSG/SEVIRI for the monitoring of aerosol optical properties at high frequencies over the Atlantic and the Mediterranean.

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