A 4-D climatology (1979–2009) of the monthly aerosol optical depth distribution over the Mediterranean region from a comparative evaluation and blending of remote sensing and model products

Abstract. Since the 1980s several spaceborne sensors have been used to retrieve the aerosol optical depth (AOD) over the Mediterranean region. In parallel, AOD climatologies coming from different numerical model simulations are now also available, permitting to distinguish the contribution of several aerosol types to the total AOD. In this work, we perform a comparative analysis of this unique multi-year database in terms of total AOD and of its apportionment by the five main aerosol types (soil dust, sea-salt, sulfate, black and organic carbon). We use 8 different satellite-derived monthly AOD products: NOAA/AVHRR, SeaWiFS, TERRA/MISR, TERRA/MODIS, AQUA/MODIS, ENVISAT/MERIS, PARASOL/POLDER and MSG/SEVIRI, as well as 3 more historical data sets: NIMBUS7/CZCS, NIMBUS7/TOMS and METEOSAT/MVIRI. Monthly model datasets include the aerosol climatology from Tegen et al. (1997), the climate-chemistry models LMDz-OR-INCA and RegCM-4, and the reanalyses GEMS and MACC. Ground-based Level-2 AERONET AOD observations from 47 stations around the basin are used here to evaluate the model and satellite data. The sensor MODIS (on AQUA and TERRA) has the best average AOD scores over this region, showing a relevant spatio-temporal variability and highlighting high dust loads over Northern Africa and the sea (spring and summer), and sulfate aerosols over continental Europe (summer). The comparison also shows limitations of certain data sets (especially MERIS and SeaWiFS standard products). Models reproduce the main patterns of the AOD variability over the basin. The MACC reanalysis is the closest to AERONET data but appears to underestimate dust over Northern Africa, where RegCM-4 is found closer to MODIS thanks to its interactive scheme for dust emissions. The vertical dimension is also investigated using the CALIOP instrument. This study confirms differences between dust aerosols which can be lifted up to 5000 m, and other continental and marine aerosols which are confined in the boundary layer. From this compilation, we propose a 4-D blended product from model and satellite data, consisting in monthly time series of 3-D aerosol distribution at a 50 km horizontal resolution over the Euro-Mediterranean marine and continental region for the 2003–2009 period. The product is based on the total AOD from AQUA/MODIS, apportioned into sulfates, black and organic carbon from the MACC reanalysis, and into dust and sea-salt aerosols from RegCM-4 simulations, which are distributed vertically based on CALIOP climatology. We extend the 2003–2009 reconstruction to the past up to 1979 using the 2003–2009 average and applying the decreasing trend in sulfate aerosols from the LMDz-OR-INCA model, based on the recent emission reconstruction proposed by Lamarque et al. (2010). Finally optical properties of the different aerosol types in this region are proposed from the literature so that this reconstruction can be included in regional climate models for aerosol radiative forcing and aerosol-climate studies.

Download Full-text

A 4-D climatology (1979–2009) of the monthly tropospheric aerosol optical depth distribution over the Mediterranean region from a comparative evaluation and blending of remote sensing and model products

Atmospheric Measurement Techniques ◽

10.5194/amt-6-1287-2013 ◽

2013 ◽

Vol 6 (5) ◽

pp. 1287-1314 ◽

Cited By ~ 90

Author(s):

P. Nabat ◽

S. Somot ◽

M. Mallet ◽

I. Chiapello ◽

J. J. Morcrette ◽

...

Keyword(s):

Organic Carbon ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Satellite Data ◽

Mediterranean Region ◽

Northern Africa ◽

Sea Salt ◽

Sulfate Aerosols ◽

The Mediterranean ◽

Aerosol Types

Abstract. Since the 1980s several spaceborne sensors have been used to retrieve the aerosol optical depth (AOD) over the Mediterranean region. In parallel, AOD climatologies coming from different numerical model simulations are now also available, permitting to distinguish the contribution of several aerosol types to the total AOD. In this work, we perform a comparative analysis of this unique multi-year database in terms of total AOD and of its apportionment by the five main aerosol types (soil dust, sea-salt, sulfate, black and organic carbon). We use 9 different satellite-derived monthly AOD products: NOAA/AVHRR, SeaWiFS (2 products), TERRA/MISR, TERRA/MODIS, AQUA/MODIS, ENVISAT/MERIS, PARASOL/POLDER and MSG/SEVIRI, as well as 3 more historical datasets: NIMBUS7/CZCS, TOMS (onboard NIMBUS7 and Earth-Probe) and METEOSAT/MVIRI. Monthly model datasets include the aerosol climatology from Tegen et al. (1997), the climate-chemistry models LMDz-OR-INCA and RegCM-4, the multi-model mean coming from the ACCMIP exercise, and the reanalyses GEMS and MACC. Ground-based Level-2 AERONET AOD observations from 47 stations around the basin are used here to evaluate the model and satellite data. The sensor MODIS (on AQUA and TERRA) has the best average AOD scores over this region, showing a relevant spatio-temporal variability and highlighting high dust loads over Northern Africa and the sea (spring and summer), and sulfate aerosols over continental Europe (summer). The comparison also shows limitations of certain datasets (especially MERIS and SeaWiFS standard products). Models reproduce the main patterns of the AOD variability over the basin. The MACC reanalysis is the closest to AERONET data, but appears to underestimate dust over Northern Africa, where RegCM-4 is found closer to MODIS thanks to its interactive scheme for dust emissions. The vertical dimension is also investigated using the CALIOP instrument. This study confirms differences of vertical distribution between dust aerosols showing a large vertical spread, and other continental and marine aerosols which are confined in the boundary layer. From this compilation, we propose a 4-D blended product from model and satellite data, consisting in monthly time series of 3-D aerosol distribution at a 50 km horizontal resolution over the Euro-Mediterranean marine and continental region for the 2003–2009 period. The product is based on the total AOD from AQUA/MODIS, apportioned into sulfates, black and organic carbon from the MACC reanalysis, and into dust and sea-salt aerosols from RegCM-4 simulations, which are distributed vertically based on CALIOP climatology. We extend the 2003–2009 reconstruction to the past up to 1979 using the 2003–2009 average and applying the decreasing trend in sulfate aerosols from LMDz-OR-INCA, whose AOD trends over Europe and the Mediterranean are median among the ACCMIP models. Finally optical properties of the different aerosol types in this region are proposed from Mie calculations so that this reconstruction can be included in regional climate models for aerosol radiative forcing and aerosol-climate studies.

Download Full-text

Application of spectral analysis techniques to the intercomparison of aerosol data – Part 4: Synthesized analysis of multisensor satellite and ground-based AOD measurements using combined maximum covariance analysis

Atmospheric Measurement Techniques ◽

10.5194/amt-7-2531-2014 ◽

2014 ◽

Vol 7 (8) ◽

pp. 2531-2549 ◽

Cited By ~ 12

Author(s):

J. Li ◽

B. E. Carlson ◽

A. A. Lacis

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Satellite Data ◽

Covariance Analysis ◽

Data Sets ◽

Data Set ◽

Maximum Covariance Analysis ◽

Source Regions ◽

Cross Covariance ◽

Aerosol Source

Abstract. In this paper, we introduce the usage of a newly developed spectral decomposition technique – combined maximum covariance analysis (CMCA) – in the spatiotemporal comparison of four satellite data sets and ground-based observations of aerosol optical depth (AOD). This technique is based on commonly used principal component analysis (PCA) and maximum covariance analysis (MCA). By decomposing the cross-covariance matrix between the joint satellite data field and Aerosol Robotic Network (AERONET) station data, both parallel comparison across different satellite data sets and the evaluation of the satellite data against the AERONET measurements are simultaneously realized. We show that this new method not only confirms the seasonal and interannual variability of aerosol optical depth, aerosol-source regions and events represented by different satellite data sets, but also identifies the strengths and weaknesses of each data set in capturing the variability associated with sources, events or aerosol types. Furthermore, by examining the spread of the spatial modes of different satellite fields, regions with the largest uncertainties in aerosol observation are identified. We also present two regional case studies that respectively demonstrate the capability of the CMCA technique in assessing the representation of an extreme event in different data sets, and in evaluating the performance of different data sets on seasonal and interannual timescales. Global results indicate that different data sets agree qualitatively for major aerosol-source regions. Discrepancies are mostly found over the Sahel, India, eastern and southeastern Asia. Results for eastern Europe suggest that the intense wildfire event in Russia during summer 2010 was less well-represented by SeaWiFS (Sea-viewing Wide Field-of-view Sensor) and OMI (Ozone Monitoring Instrument), which might be due to misclassification of smoke plumes as clouds. Analysis for the Indian subcontinent shows that here SeaWiFS agrees best with AERONET in terms of seasonality for both the Gangetic Basin and southern India, while on interannual timescales it has the poorest agreement.

Download Full-text

Interpreting the cloud cover – aerosol optical depth relationship found in satellite data using a general circulation model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-26013-2009 ◽

2009 ◽

Vol 9 (6) ◽

pp. 26013-26027 ◽

Cited By ~ 1

Author(s):

J. Quaas ◽

B. Stevens ◽

P. Stier ◽

U. Lohmann

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Satellite Data ◽

General Circulation ◽

Cloud Cover ◽

Positive Relationship ◽

Climate Model ◽

Circulation Model ◽

Data Sets ◽

Depth Relationship

Abstract. Statistical analysis of satellite data shows a positive correlation between aerosol optical depth (AOD) and total cloud cover (TCC). Here we compare the slope of the linear regression between the logarithm of TCC and the logarithm of AOD, or the strength of the relationship, as derived from three satellite data sets to the ones simulated by a global aerosol-climate model. We analyze model results from two different simulations with and without a parameterization of aerosol indirect effects, and using dry compared to humidified AOD. We find that none of the hypotheses discussed in the literature is able to uniquely explain the positive relationship. The most important contribution in the model is from the swelling of aerosol in the vicinity of clouds, where relative humidity is high. The model also shows contribution of the aerosol cloud lifetime effect to the positive relationship, which, however, is of lesser importance.

Download Full-text

Spatio-temporal assessment of Aerosol Optical Depth from Himawari-8 satellite data over Malaysia

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/540/1/012053 ◽

2020 ◽

Vol 540 ◽

pp. 012053

Author(s):

Nurul Amalin Fatihah Kamarul Zaman ◽

Kasturi Devi Kanniah

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Satellite Data ◽

Spatio Temporal ◽

Temporal Assessment

Download Full-text

Application of spectral analysis techniques in the intercomparison of aerosol data: 1. An EOF approach to analyze the spatial-temporal variability of aerosol optical depth using multiple remote sensing data sets

Journal of Geophysical Research Atmospheres ◽

10.1002/jgrd.50686 ◽

2013 ◽

Vol 118 (15) ◽

pp. 8640-8648 ◽

Cited By ~ 27

Author(s):

Jing Li ◽

Barbara E. Carlson ◽

Andrew A. Lacis

Keyword(s):

Remote Sensing ◽

Spectral Analysis ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Temporal Variability ◽

Remote Sensing Data ◽

Data Sets ◽

Sensing Data ◽

Analysis Techniques

Download Full-text

The potential of elastic and polarization lidars to retrieve extinction profiles

Atmospheric Measurement Techniques ◽

10.5194/amt-13-893-2020 ◽

2020 ◽

Vol 13 (2) ◽

pp. 893-905 ◽

Cited By ~ 5

Author(s):

Elina Giannakaki ◽

Panos Kokkalis ◽

Eleni Marinou ◽

Nikolaos S. Bartsotas ◽

Vassilis Amiridis ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Dust Particles ◽

Depolarization Ratio ◽

Lidar System ◽

Lidar Measurements ◽

Lidar Ratio ◽

Linear Depolarization Ratio ◽

Aerosol Types ◽

532 Nm

Abstract. A new method, called ElEx (elastic extinction), is proposed for the estimation of extinction coefficient lidar profiles using only the information provided by the elastic and polarization channels of a lidar system. The method is applicable to lidar measurements both during daytime and nighttime under well-defined aerosol mixtures. ElEx uses the particle backscatter profiles at 532 nm and the vertically resolved particle linear depolarization ratio measurements at the same wavelength. The particle linear depolarization ratio and the lidar ratio values of pure aerosol types are also taken from literature. The total extinction profile is then estimated and compared well with Raman retrievals. In this study, ElEx was applied in an aerosol mixture of marine and dust particles at Finokalia station during the CHARADMExp campaign. Any difference between ElEx and Raman extinction profiles indicates that the nondust component could be probably attributed to polluted marine or polluted continental aerosols. Comparison with sun photometer aerosol optical depth observations is performed as well during daytime. Differences in the total aerosol optical depth are varying between 1.2 % and 72 %, and these differences are attributed to the limited ability of the lidar to correctly represent the aerosol optical properties in the near range due to the overlap problem.

Download Full-text

Understanding the aerosol information content in multi-spectral reflectance measurements using a synergetic retrieval algorithm

Atmospheric Measurement Techniques ◽

10.5194/amt-3-1589-2010 ◽

2010 ◽

Vol 3 (6) ◽

pp. 1589-1598 ◽

Cited By ~ 8

Author(s):

D. Martynenko ◽

T. Holzer-Popp ◽

H. Elbern ◽

M. Schroedter-Homscheidt

Keyword(s):

Content Analysis ◽

Information Content ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Degrees Of Freedom ◽

Surface Albedo ◽

Water Soluble ◽

Retrieval Algorithm ◽

Aerosol Types ◽

Reflectance Measurements

Abstract. An information content analysis for multi-wavelength SYNergetic AErosol Retrieval algorithm SYNAER was performed to quantify the number of independent pieces of information that can be retrieved. In particular, the capability of SYNAER to discern various aerosol types is assessed. This information content depends on the aerosol optical depth, the surface albedo spectrum and the observation geometry. The theoretical analysis is performed for a large number of scenarios with various geometries and surface albedo spectra for ocean, soil and vegetation. When the surface albedo spectrum and its accuracy is known under cloud-free conditions, reflectance measurements used in SYNAER is able to provide for 2–4° of freedom that can be attributed to retrieval parameters: aerosol optical depth, aerosol type and surface albedo. The focus of this work is placed on an information content analysis with emphasis to the aerosol type classification. This analysis is applied to synthetic reflectance measurements for 40 predefined aerosol mixtures of different basic components, given by sea salt, mineral dust, biomass burning and diesel aerosols, water soluble and water insoluble aerosols. The range of aerosol parameters considered through the 40 mixtures covers the natural variability of tropospheric aerosols. After the information content analysis performed in Holzer-Popp et al. (2008) there was a necessity to compare derived degrees of freedom with retrieved aerosol optical depth for different aerosol types, which is the main focus of this paper. The principle component analysis was used to determine the correspondence between degrees of freedom for signal in the retrieval and derived aerosol types. The main results of the analysis indicate correspondence between the major groups of the aerosol types, which are: water soluble aerosol, soot, mineral dust and sea salt and degrees of freedom in the algorithm and show the ability of the SYNAER to discern between this aerosol types. The results of the work will be further used for the development of the promising methodology of the construction error covariance matrices in the assimilation system.

Download Full-text

Retrieval of aerosol optical depth in vicinity of broken clouds from reflectance ratios: case study

Atmospheric Measurement Techniques ◽

10.5194/amt-3-1333-2010 ◽

2010 ◽

Vol 3 (5) ◽

pp. 1333-1349 ◽

Cited By ~ 9

Author(s):

E. Kassianov ◽

M. Ovchinnikov ◽

L. K. Berg ◽

S. A. McFarlane ◽

C. Flynn ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Great Plains ◽

Land Surface ◽

Single Layer ◽

Department Of Energy ◽

High Spectral Resolution ◽

Data Sets ◽

Atmospheric Radiation Measurement

Abstract. A recently developed reflectance ratio (RR) method for the retrieval of aerosol optical depth (AOD) is evaluated using extensive airborne and ground-based data sets collected during the Cloud and Land Surface Interaction Campaign (CLASIC) and the Cumulus Humilis Aerosol Processing Study (CHAPS), which took place in June 2007 over the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains site. A detailed case study is performed for a field of single-layer shallow cumuli observed on 12 June 2007. The RR method is applied to retrieve the spectral values of AOD from the reflectance ratios measured by the MODIS Airborne Simulator (MAS) for two pairs of wavelengths (660 and 470 nm, 870 and 470 nm) collected at a spatial resolution of 0.05 km. The retrieval is compared with an independent AOD estimate from three ground-based Multi-filter Rotating Shadowband Radiometers (MFRSRs). The interpolation algorithm that is used to project MFRSR point measurements onto the aircraft flight tracks is tested using AOD derived from NASA Langley High Spectral Resolution Lidar (HSRL). The RR AOD estimates are in a good agreement (within 5%) with the MFRSR-derived AOD values for the 660-nm wavelength. The AODs obtained from MAS reflectance ratios overestimate those derived from MFRSR measurements by 15–30% for the 470-nm wavelength and underestimate the 870-nm AOD by the same amount.

Download Full-text