Consistency of aerosols above clouds characterization from A-Train active and passive measurements
This study presents a comparison between the retrieval of optical properties of aerosol above clouds (AAC) from different techniques developed for the A-Train sensors CALIOP/CALIPSO and POLDER/PARASOL. The main objective is to analyse the consistency between the results derived from the active and t...
Published in: | Atmospheric Measurement Techniques |
---|---|
Main Authors: | , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2017
|
Subjects: | |
Online Access: | https://doi.org/10.5194/amt-10-3499-2017 https://noa.gwlb.de/receive/cop_mods_00008645 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00008602/amt-10-3499-2017.pdf https://amt.copernicus.org/articles/10/3499/2017/amt-10-3499-2017.pdf |
id |
ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00008645 |
---|---|
record_format |
openpolar |
institution |
Open Polar |
collection |
Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Deaconu, Lucia T. Waquet, Fabien Josset, Damien Ferlay, Nicolas Peers, Fanny Thieuleux, François Ducos, Fabrice Pascal, Nicolas Tanré, Didier Pelon, Jacques Goloub, Philippe Consistency of aerosols above clouds characterization from A-Train active and passive measurements |
topic_facet |
article Verlagsveröffentlichung |
description |
This study presents a comparison between the retrieval of optical properties of aerosol above clouds (AAC) from different techniques developed for the A-Train sensors CALIOP/CALIPSO and POLDER/PARASOL. The main objective is to analyse the consistency between the results derived from the active and the passive measurements. We compare the aerosol optical thickness (AOT) above optically thick clouds (cloud optical thickness (COT) larger than 3) and their Ångström exponent (AE). These parameters are retrieved with the CALIOP operational method, the POLDER operational polarization method and the CALIOP-based depolarization ratio method (DRM) – for which we also propose a calibrated version (denominated DRMSODA, where SODA is the Synergized Optical Depth of Aerosols). We analyse 6 months of data over three distinctive regions characterized by different types of aerosols and clouds. Additionally, for these regions, we select three case studies: a biomass-burning event over the South Atlantic Ocean, a Saharan dust case over the North Atlantic Ocean and a Siberian biomass-burning event over the North Pacific Ocean. Four and a half years of data are studied over the entire globe for distinct situations where aerosol and cloud layers are in contact or vertically separated. Overall, the regional analysis shows a good correlation between the POLDER and the DRMSODA AOTs when the microphysics of aerosols is dominated by fine-mode particles of biomass-burning aerosols from southern Africa (correlation coefficient (R2) of 0.83) or coarse-mode aerosols of Saharan dust (R2 of 0.82). A good correlation between these methods (R2 of 0.68) is also observed in the global treatment, when the aerosol and cloud layers are separated well. The analysis of detached layers also shows a mean difference in AOT of 0.07 at 532 nm between POLDER and DRMSODA at a global scale. The correlation between the retrievals decreases when a complex mixture of aerosols is expected (R2 of 0.37) – as in the East Asia region – and when the aerosol–cloud layers are in contact (R2 of 0.36). The correlation coefficient between the CALIOP operational method and POLDER is found to be low, as the CALIOP method largely underestimates the aerosol loading above clouds by a factor that ranges from 2 to 4. Potential biases on the retrieved AOT as a function of cloud properties are also investigated. For different types of scenes, the retrieval of above-cloud AOT from POLDER and from DRM are compared for different underlying cloud properties (droplet effective radius (reff) and COT retrieved with MODIS). The results reveal that DRM AOT vary with reff. When accounting for reff in the DRM algorithm, the consistency between the methods increases. The sensitivity study shows that an additional polarized signal coming from aerosols located within the cloud could affect the polarization method, which leads to an overestimation of the AOT retrieved with POLDER algorithm. In addition, the aerosols attached to or within the cloud can potentially impact the DRM retrievals through the modification of the cloud droplet chemical composition and its ability to backscatter light. The next step of this work is to combine POLDER and CALIOP to investigate the impacts of aerosols on clouds and climate when these particles are transported above or within clouds. |
format |
Article in Journal/Newspaper |
author |
Deaconu, Lucia T. Waquet, Fabien Josset, Damien Ferlay, Nicolas Peers, Fanny Thieuleux, François Ducos, Fabrice Pascal, Nicolas Tanré, Didier Pelon, Jacques Goloub, Philippe |
author_facet |
Deaconu, Lucia T. Waquet, Fabien Josset, Damien Ferlay, Nicolas Peers, Fanny Thieuleux, François Ducos, Fabrice Pascal, Nicolas Tanré, Didier Pelon, Jacques Goloub, Philippe |
author_sort |
Deaconu, Lucia T. |
title |
Consistency of aerosols above clouds characterization from A-Train active and passive measurements |
title_short |
Consistency of aerosols above clouds characterization from A-Train active and passive measurements |
title_full |
Consistency of aerosols above clouds characterization from A-Train active and passive measurements |
title_fullStr |
Consistency of aerosols above clouds characterization from A-Train active and passive measurements |
title_full_unstemmed |
Consistency of aerosols above clouds characterization from A-Train active and passive measurements |
title_sort |
consistency of aerosols above clouds characterization from a-train active and passive measurements |
publisher |
Copernicus Publications |
publishDate |
2017 |
url |
https://doi.org/10.5194/amt-10-3499-2017 https://noa.gwlb.de/receive/cop_mods_00008645 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00008602/amt-10-3499-2017.pdf https://amt.copernicus.org/articles/10/3499/2017/amt-10-3499-2017.pdf |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
North Atlantic South Atlantic Ocean |
genre_facet |
North Atlantic South Atlantic Ocean |
op_relation |
Atmospheric Measurement Techniques -- http://www.bibliothek.uni-regensburg.de/ezeit/?2505596 -- http://www.atmospheric-measurement-techniques.net/ -- 1867-8548 https://doi.org/10.5194/amt-10-3499-2017 https://noa.gwlb.de/receive/cop_mods_00008645 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00008602/amt-10-3499-2017.pdf https://amt.copernicus.org/articles/10/3499/2017/amt-10-3499-2017.pdf |
op_rights |
uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/amt-10-3499-2017 |
container_title |
Atmospheric Measurement Techniques |
container_volume |
10 |
container_issue |
9 |
container_start_page |
3499 |
op_container_end_page |
3523 |
_version_ |
1766137321506209792 |
spelling |
ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00008645 2023-05-15T17:37:24+02:00 Consistency of aerosols above clouds characterization from A-Train active and passive measurements Deaconu, Lucia T. Waquet, Fabien Josset, Damien Ferlay, Nicolas Peers, Fanny Thieuleux, François Ducos, Fabrice Pascal, Nicolas Tanré, Didier Pelon, Jacques Goloub, Philippe 2017-09 electronic https://doi.org/10.5194/amt-10-3499-2017 https://noa.gwlb.de/receive/cop_mods_00008645 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00008602/amt-10-3499-2017.pdf https://amt.copernicus.org/articles/10/3499/2017/amt-10-3499-2017.pdf eng eng Copernicus Publications Atmospheric Measurement Techniques -- http://www.bibliothek.uni-regensburg.de/ezeit/?2505596 -- http://www.atmospheric-measurement-techniques.net/ -- 1867-8548 https://doi.org/10.5194/amt-10-3499-2017 https://noa.gwlb.de/receive/cop_mods_00008645 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00008602/amt-10-3499-2017.pdf https://amt.copernicus.org/articles/10/3499/2017/amt-10-3499-2017.pdf uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 2017 ftnonlinearchiv https://doi.org/10.5194/amt-10-3499-2017 2022-02-08T22:57:56Z This study presents a comparison between the retrieval of optical properties of aerosol above clouds (AAC) from different techniques developed for the A-Train sensors CALIOP/CALIPSO and POLDER/PARASOL. The main objective is to analyse the consistency between the results derived from the active and the passive measurements. We compare the aerosol optical thickness (AOT) above optically thick clouds (cloud optical thickness (COT) larger than 3) and their Ångström exponent (AE). These parameters are retrieved with the CALIOP operational method, the POLDER operational polarization method and the CALIOP-based depolarization ratio method (DRM) – for which we also propose a calibrated version (denominated DRMSODA, where SODA is the Synergized Optical Depth of Aerosols). We analyse 6 months of data over three distinctive regions characterized by different types of aerosols and clouds. Additionally, for these regions, we select three case studies: a biomass-burning event over the South Atlantic Ocean, a Saharan dust case over the North Atlantic Ocean and a Siberian biomass-burning event over the North Pacific Ocean. Four and a half years of data are studied over the entire globe for distinct situations where aerosol and cloud layers are in contact or vertically separated. Overall, the regional analysis shows a good correlation between the POLDER and the DRMSODA AOTs when the microphysics of aerosols is dominated by fine-mode particles of biomass-burning aerosols from southern Africa (correlation coefficient (R2) of 0.83) or coarse-mode aerosols of Saharan dust (R2 of 0.82). A good correlation between these methods (R2 of 0.68) is also observed in the global treatment, when the aerosol and cloud layers are separated well. The analysis of detached layers also shows a mean difference in AOT of 0.07 at 532 nm between POLDER and DRMSODA at a global scale. The correlation between the retrievals decreases when a complex mixture of aerosols is expected (R2 of 0.37) – as in the East Asia region – and when the aerosol–cloud layers are in contact (R2 of 0.36). The correlation coefficient between the CALIOP operational method and POLDER is found to be low, as the CALIOP method largely underestimates the aerosol loading above clouds by a factor that ranges from 2 to 4. Potential biases on the retrieved AOT as a function of cloud properties are also investigated. For different types of scenes, the retrieval of above-cloud AOT from POLDER and from DRM are compared for different underlying cloud properties (droplet effective radius (reff) and COT retrieved with MODIS). The results reveal that DRM AOT vary with reff. When accounting for reff in the DRM algorithm, the consistency between the methods increases. The sensitivity study shows that an additional polarized signal coming from aerosols located within the cloud could affect the polarization method, which leads to an overestimation of the AOT retrieved with POLDER algorithm. In addition, the aerosols attached to or within the cloud can potentially impact the DRM retrievals through the modification of the cloud droplet chemical composition and its ability to backscatter light. The next step of this work is to combine POLDER and CALIOP to investigate the impacts of aerosols on clouds and climate when these particles are transported above or within clouds. Article in Journal/Newspaper North Atlantic South Atlantic Ocean Niedersächsisches Online-Archiv NOA Pacific Atmospheric Measurement Techniques 10 9 3499 3523 |