scholarly journals Optimizing Saharan dust CALIPSO retrievals

2013 ◽  
Vol 13 (6) ◽  
pp. 14749-14795 ◽  
Author(s):  
V. Amiridis ◽  
U. Wandinger ◽  
E. Marinou ◽  
E. Giannakaki ◽  
A. Tsekeri ◽  
...  
Keyword(s):  
North Africa ◽  
Saharan Dust ◽  
Individual Level ◽  
Dust Extinction ◽  
Absolute Bias ◽  
Level 3 ◽  
Lidar Ratio ◽  
Aerosol Types ◽  
Level 2 ◽  
Good Agreement

Abstract. We demonstrate improvements in CALIPSO dust extinction retrievals over North Africa and Europe when corrections are applied regarding the Saharan dust lidar ratio assumption, the separation of dust portion in detected dust mixtures, and the averaging scheme introduced in the Level 3 CALIPSO product. First, a universal, spatially constant lidar ratio of 58 sr instead of 40 sr is applied to individual Level 2 dust-related backscatter products. The resulting aerosol optical depths show an improvement compared with synchronous and co-located AERONET measurements. An absolute bias of the order of −0.03 has been found, improving on the statistically significant biases of the order of −0.10 reported in the literature for the original CALIPSO product. When compared with the MODIS co-located AOD product, the CALIPSO negative bias is even less for the lidar ratio of 58 sr. After introducing the new lidar ratio for the domain studied, we examine potential improvements to the climatological CALIPSO Level 3 extinction product: (1) by introducing a new methodology for the calculation of pure dust extinction from dust mixtures and (2) by applying an averaging scheme that includes zero extinction values for the non-dust aerosol types detected. The scheme is applied at a horizontal spatial resolution of 1° × 1° for ease of comparison with the instantaneous and co-located dust extinction profiles simulated by the BSC-DREAM8b dust model. Comparisons show that the extinction profiles retrieved with the proposed methodology reproduce the well-known model biases per sub-region examined. The very good agreement of the proposed CALIPSO extinction product with respect to AERONET, MODIS and the BSC-DREAM8b dust model, makes this dataset an ideal candidate for the provision of an accurate and robust multi-year dust climatology over North Africa and Europe.

scholarly journals Optimizing CALIPSO Saharan dust retrievals

2013 ◽  
Vol 13 (23) ◽  
pp. 12089-12106 ◽  
Author(s):  
V. Amiridis ◽  
U. Wandinger ◽  
E. Marinou ◽  
E. Giannakaki ◽  
A. Tsekeri ◽  
...  
Keyword(s):  
Northern Africa ◽  
Saharan Dust ◽  
Individual Level ◽  
Dust Extinction ◽  
Absolute Bias ◽  
Moderate Resolution ◽  
Level 3 ◽  
Lidar Ratio ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. We demonstrate improvements in CALIPSO (Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations) dust extinction retrievals over northern Africa and Europe when corrections are applied regarding the Saharan dust lidar ratio assumption, the separation of the dust portion in detected dust mixtures, and the averaging scheme introduced in the Level 3 CALIPSO product. First, a universal, spatially constant lidar ratio of 58 sr instead of 40 sr is applied to individual Level 2 dust-related backscatter products. The resulting aerosol optical depths show an improvement compared with synchronous and collocated AERONET (Aerosol Robotic Network) measurements. An absolute bias of the order of −0.03 has been found, improving on the statistically significant biases of the order of −0.10 reported in the literature for the original CALIPSO product. When compared with the MODIS (Moderate-Resolution Imaging Spectroradiometer) collocated aerosol optical depth (AOD) product, the CALIPSO negative bias is even less for the lidar ratio of 58 sr. After introducing the new lidar ratio for the domain studied, we examine potential improvements to the climatological CALIPSO Level 3 extinction product: (1) by introducing a new methodology for the calculation of pure dust extinction from dust mixtures and (2) by applying an averaging scheme that includes zero extinction values for the nondust aerosol types detected. The scheme is applied at a horizontal spatial resolution of 1° × 1° for ease of comparison with the instantaneous and collocated dust extinction profiles simulated by the BSC-DREAM8b dust model. Comparisons show that the extinction profiles retrieved with the proposed methodology reproduce the well-known model biases per subregion examined. The very good agreement of the proposed CALIPSO extinction product with respect to AERONET, MODIS and the BSC-DREAM8b dust model makes this dataset an ideal candidate for the provision of an accurate and robust multiyear dust climatology over northern Africa and Europe.

scholarly journals Use of the CALIOP vertical feature mask for evaluating global aerosol models

2015 ◽  
Vol 8 (1) ◽  
pp. 1401-1455 ◽  
Author(s):  
E. P. Nowottnick ◽  
P. R. Colarco ◽  
E. J. Welton ◽  
A. da Silva
Keyword(s):  
Simulation Experiment ◽  
Saharan Dust ◽  
System Model ◽  
Marine Aerosols ◽  
Earth Observing System ◽  
Level 3 ◽  
Observing System Simulation Experiment ◽  
Modern Era ◽  
Aerosol Types ◽  
Level 2

Abstract. Global aerosol distributions provided by the NASA Modern Era Retrospective Analysis for Research and Applications aerosol reanalysis (MERRAero) are evaluated using the aerosol types identified by the CALIOP vertical feature mask (VFM) algorithm, focusing especially on Saharan dust distributions during July 2009. MERRAero is comprised of an aerosol simulation produced in the Goddard Earth Observing System version 5 (GEOS-5) Earth system model and incorporates assimilation of MODIS-derived aerosol optical thickness to constrain column aerosol loadings. For comparison to the CALIOP VFM we construct two synthetic VFMs using the MERRAero aerosol distributions: a Level 2 VFM in which simulated MERRAero total attenuated backscatter and estimated particulate depolarization ratios are input directly to the CALIOP VFM typing algorithm, and a Level 3 VFM in which we map the aerosol species in MERRAero to the CALIOP VFM types. By comparing the simulated MERRAero-Level 2 VFM to CALIOP VFM we can diagnose the aerosol transport and speciation in MERRAero. By comparing the MERRAero-Level 2 and MERRAero-Level 3 simulated VFMs we perform a simple Observing System Simulation Experiment (OSSE), which is useful for identifying shortcomings in the CALIOP VFM algorithm itself. We find that despite having our column AOT constrained by MODIS, comparison to the CALIOP VFM reveals a greater occurrence of dusty aerosol layers in our MERRAero-Level 2 VFM, due to errors in MERRAero aerosol speciation. Additionally, we find that the CALIOP VFM algorithm classification for desert dust and polluted dust should be reconsidered for aerosol features that contain dust mixtures in low aerosol loadings, as our application of the CALIOP VFM to MERRAero distributions flagged a greater presence of dusty vs. marine aerosols when our two MERRAero VFMs were compared.

scholarly journals EARLINET dust observations vs. BSC-DREAM8b modeled profiles: 12-year-long systematic comparison at Potenza, Italy

2014 ◽  
Vol 14 (16) ◽  
pp. 8781-8793 ◽  
Author(s):  
L. Mona ◽  
N. Papagiannopoulos ◽  
S. Basart ◽  
J. Baldasano ◽  
I. Binietoglou ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Saharan Dust ◽  
Raman Lidar ◽  
Dust Layer ◽  
Systematic Comparison ◽  
Dust Extinction ◽  
Lidar Measurements ◽  
Order Of Magnitude ◽  
Lidar Ratio ◽  
532 Nm

Abstract. In this paper, we report the first systematic comparison of 12-year modeled dust extinction profiles vs. Raman lidar measurements. We use the BSC-DREAM8b model, one of the most widely used dust regional models in the Mediterranean, and Potenza EARLINET lidar profiles for Saharan dust cases, the largest one-site database of dust extinction profiles. A total of 310 dust cases were compared for the May 2000–July 2012 period. The model reconstructs the measured layers well: profiles are correlated within 5% of significance for 60% of the cases and the dust layer center of mass as measured by lidar and modeled by BSC-DREAM8b differ on average 0.3 ± 1.0 km. Events with a dust optical depth lower than 0.1 account for 70% of uncorrelated profiles. Although there is good agreement in terms of profile shape and the order of magnitude of extinction values, the model overestimates the occurrence of dust layer top above 10 km. Comparison with extinction profiles measured by the Raman lidar shows that BSC-DREAM8b typically underestimates the dust extinction coefficient, in particular below 3 km. Lowest model–observation differences (below 17%) correspond to a lidar ratio at 532 nm and Ångström exponent at 355/532 nm of 60 ± 13 and 0.1 ± 0.6 sr, respectively. These are in agreement with values typically observed and modeled for pure desert dust. However, the highest differences (higher than 85%) are typically related to greater Ångström values (0.5 ± 0.6), denoting smaller particles. All these aspects indicate that the level of agreement decreases with an increase in mixing/modification processes.

scholarly journals Modeling PM10 Originating from Dust Intrusions in the Southern Iberian Peninsula Using HYSPLIT

2011 ◽  
Vol 26 (2) ◽  
pp. 236-242 ◽  
Author(s):  
A. F. Stein ◽  
Y. Wang ◽  
J. D. de la Rosa ◽  
A. M. Sanchez de la Campa ◽  
Nuria Castell ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Statistical Analysis ◽  
Iberian Peninsula ◽  
North Africa ◽  
Saharan Dust ◽  
Hysplit Model ◽  
Spatial And Temporal Distributions ◽  
Background Measurement ◽  
Good Agreement ◽  
Surface Background

Abstract The Hybrid Single-Particle Lagrangian Integrated Trajectories (HYSPLIT) model has been applied to calculate the spatial and temporal distributions of dust originating from North Africa. The model has been configured to forecast hourly particulate matter ≤10 μm (PM10) dust concentrations focusing on the impacts over the southern Iberian Peninsula. Two full years (2008 and 2009) have been simulated and compared against surface background measurement sites. A statistical analysis using discrete and categorical evaluations is presented. The model is capable of simulating the occurrence of Saharan dust episodes as observed at the measurement stations and captures the generally higher levels observed in eastern Andalusia, Spain, with respect to the western Andalusia station. But the simulation tends to underpredict the magnitude of the dust concentration peaks. The model has also been qualitatively compared with satellite data, showing generally good agreement in the spatial distribution of the dust column.

scholarly journals Optical properties of different aerosol types: seven years of combined Raman-elastic backscatter lidar measurements in Thessaloniki, Greece

2010 ◽  
Vol 3 (3) ◽  
pp. 569-578 ◽  
Author(s):  
E. Giannakaki ◽  
D. S. Balis ◽  
V. Amiridis ◽  
C. Zerefos
Keyword(s):  
Saharan Dust ◽  
Downward Movement ◽  
Angstrom Exponent ◽  
Lidar Measurements ◽  
Ångström Exponent ◽  
Lidar Ratio ◽  
Local Path ◽  
Aerosol Types ◽  
Lidar Observations ◽  
Ångstrom Exponent

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol particles. For local and continental polluted aerosols the measurements indicate high aerosol loads. However, measurements associated with the local path indicate enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for continental aerosols, from West directions with less free tropospheric contribution. The largest lidar ratios, of the order of 70 sr, are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values were estimated for different aerosol categories. Scatter plot between lidar ratio values and Ångström exponent values for local and continental polluted aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for continental aerosols with west and northwest directions that follow downward movement when arriving at our site constantly low lidar ratios almost independent of size are found.

scholarly journals Optical properties of different aerosol types: seven years of combined Raman- elastic backscatter lidar measurements in Thessaloniki, Greece

2009 ◽  
Vol 2 (6) ◽  
pp. 3027-3054
Author(s):  
E. Giannakaki ◽  
D. S. Balis ◽  
V. Amiridis ◽  
C. Zerefos
Keyword(s):  
Saharan Dust ◽  
Scatter Plot ◽  
Angstrom Exponent ◽  
Lidar Measurements ◽  
Ångström Exponent ◽  
Lidar Ratio ◽  
Local Path ◽  
Aerosol Types ◽  
Lidar Observations ◽  
Ångstrom Exponent

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol loads. For "local" and "continental polluted" aerosols the measurements indicate moderate aerosol loads. However, measurements associated with the "local" path show lower values of free tropospheric contribution (37% versus 46% for "continental polluted") and thus, enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for "continental clean" aerosols. The largest lidar ratios, of the order of 70 sr are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values was estimated for well defined aerosol categories, which provides a statistical measure of the lidar ratio's dependency on aerosol-size, which is a useful tool for elastic lidar systems. Scatter plot between lidar ratio values and Ångström exponent values for "local" and "continental polluted" aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for "clean continental" aerosols we found constantly low lidar ratios almost independent of size.

scholarly journals Systematic comparison of dust BSC-DREAM8b modeled profiles with Potenza EARLINET lidar database

2013 ◽  
Vol 13 (12) ◽  
pp. 31363-31407
Author(s):  
L. Mona ◽  
N. Papagiannopoulos ◽  
S. Basart ◽  
J. Baldasano ◽  
I. Binietoglou ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Saharan Dust ◽  
Raman Lidar ◽  
Regional Models ◽  
Dust Layer ◽  
Systematic Comparison ◽  
Dust Extinction ◽  
Low Concentrations ◽  
Order Of Magnitude ◽  
Good Agreement

Abstract. In this paper, we report the first systematic comparison between dust extinction profiles forecasted by a model and measured by a Raman lidar. We use the BSC-DREAM8b model, one of the most widely used dust regional models in the Mediterranean, and Potenza EARLINET lidar profiles for Saharan dust cases, the largest one-site database of dust extinction profiles. A total of 310 dust cases were compared for the May 2000–July 2012 period. The model well reconstructs the measured layering: profiles are correlated within 5% of significance for 60% of the cases and the dust layer center of mass as measured by lidar and modeled by BSC-DREAM8b differ on average 0.3 ± 1.0 km. Cases with a dust optical depth lower than 0.1 account for 70% of uncorrelated profiles. Although the good agreement in terms of profile shape and extinction value order of magnitude, the comparison with extinction profiles measured by the Raman lidar shows that BSC-DREAM8b typically underestimate the dust extinction coefficient in particular below 3.5 km and for low concentrations and overestimates the occurrence of dust layer top height above 15 km.

scholarly journals The GOME-type Total Ozone Essential Climate Variable (GTO-ECV) data record from the ESA Climate Change Initiative

2015 ◽  
Vol 8 (5) ◽  
pp. 4607-4652 ◽  
Author(s):  
M. Coldewey-Egbers ◽  
D. G. Loyola ◽  
M. Koukouli ◽  
D. Balis ◽  
J.-C. Lambert ◽  
...  
Keyword(s):  
Climate Change ◽  
Total Ozone ◽  
Climate Model ◽  
Change Initiative ◽  
Climate Variable ◽  
Individual Level ◽  
Data Record ◽  
Level 3 ◽  
Level 2

Abstract. We present the new GOME-type Total Ozone Essential Climate Variable (GTO-ECV) data record which has been created within the framework of the European Space Agency's Climate Change Initiative (ESA-CCI). Total ozone column observations – based on the GOME-type Direct Fitting version 3 algorithm – from GOME (Global Ozone Monitoring Experiment), SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY), and GOME-2 have been combined into one homogeneous time series, thereby taking advantage of the high inter-sensor consistency. The data record spans the 15-year period from March 1996 to June 2011 and it contains global monthly mean total ozone columns on a 1° × 1° grid. Geophysical ground-based validation using Brewer, Dobson, and UV-visible instruments has shown that the GTO-ECV level 3 data record is of the same high quality as the equivalent individual level 2 data products that constitute it. Both absolute agreement and long-term stability are excellent with respect to the ground-based data, for almost all latitudes apart from a few outliers which are mostly due to sampling differences between the level 2 and level 3 data. We conclude that the GTO-ECV data record is valuable for a variety of climate applications such as the long-term monitoring of the past evolution of the ozone layer, trend analysis and the evaluation of Chemistry–Climate Model simulations.

scholarly journals The CALIPSO Automated Aerosol Classification and Lidar Ratio Selection Algorithm

2009 ◽  
Vol 26 (10) ◽  
pp. 1994-2014 ◽  
Author(s):  
Ali H. Omar ◽  
David M. Winker ◽  
Mark A. Vaughan ◽  
Yongxiang Hu ◽  
Charles R. Trepte ◽  
...  
Keyword(s):  
Identification Algorithm ◽  
Surface Type ◽  
Aerosol Classification ◽  
Lidar Ratio ◽  
One Year ◽  
Aerosol Types ◽  
532 Nm ◽  
Level 2 ◽  
Aerosol Type

Abstract Descriptions are provided of the aerosol classification algorithms and the extinction-to-backscatter ratio (lidar ratio) selection schemes for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) aerosol products. One year of CALIPSO level 2 version 2 data are analyzed to assess the veracity of the CALIPSO aerosol-type identification algorithm and generate vertically resolved distributions of aerosol types and their respective optical characteristics. To assess the robustness of the algorithm, the interannual variability is analyzed by using a fixed season (June–August) and aerosol type (polluted dust) over two consecutive years (2006 and 2007). The CALIPSO models define six aerosol types: clean continental, clean marine, dust, polluted continental, polluted dust, and smoke, with 532-nm (1064 nm) extinction-to-backscatter ratios Sa of 35 (30), 20 (45), 40 (55), 70 (30), 65 (30), and 70 (40) sr, respectively. This paper presents the global distributions of the CALIPSO aerosol types, the complementary distributions of integrated attenuated backscatter, and the volume depolarization ratio for each type. The aerosol-type distributions are further partitioned according to surface type (land/ocean) and detection resolution (5, 20, and 80 km) for optical and spatial context, because the optically thick layers are found most often at the smallest spatial resolution. Except for clean marine and polluted continental, all the aerosol types are found preferentially at the 80-km resolution. Nearly 80% of the smoke cases and 60% of the polluted dust cases are found over water, whereas dust and polluted continental cases are found over both land and water at comparable frequencies. Because the CALIPSO observables do not sufficiently constrain the determination of the aerosol, the surface type is used to augment the selection criteria. Distributions of the total attenuated color ratios show that the use of surface type in the typing algorithm does not result in abrupt and artificial changes in aerosol type or extinction.

scholarly journals A Decade of CALIPSO Observations of Asian and Saharan Dust Properties near Source and Transport Regions

2019 ◽  
Vol 99 ◽  
pp. 02008
Author(s):  
Ali Omar
Keyword(s):  
Distribution Functions ◽  
Satellite Observations ◽  
Saharan Dust ◽  
Small Scale ◽  
Far Field ◽  
Probability Distribution Functions ◽  
Level 3 ◽  
Lidar Ratio ◽  
Robust Measurements ◽  
Transport Region

The lidar on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, makes robust measurements of dust and has generated a length of record that is significant both seasonally and inter-annually. We exploit this record to determine a multi-year climatology of the properties of Asian and Saharan dust, in particular seasonal optical depths, layer frequencies, and layer heights of dust gridded in accordance with the Level 3 data products protocol between 2006 and 2016. The data are screened using standard CALIPSO quality assurance flags, cloud aerosol discrimination (CAD) scores, overlying features and layer properties. To evaluate the effects of transport on small-scale phenomena such as morphology, vertical extent and size of the dust layers, we compare probability distribution functions of the layer integrated volume depolarization ratios, geometric depths and integrated attenuated color ratios near the source to the same distributions in the far field or transport region. To evaluate the uncertainty in the lidar ratios, we compare the values computed from dust layers overlying opaque water clouds, considered accurate, with the constant lidar ratio value used in the CALIOP algorithms for dust

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