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Atmos. Meas. Tech., 10, 4439-4457, 2017
https://doi.org/10.5194/amt-10-4439-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
17 Nov 2017
Comparative assessment of GRASP algorithm for a dust event over Granada (Spain) during ChArMEx-ADRIMED 2013 campaign
Jose A. Benavent-Oltra1,2, Roberto Román1,2, María J. Granados-Muñoz1,2, Daniel Pérez-Ramírez1,2, Pablo Ortiz-Amezcua1,2, Cyrielle Denjean3, Anton Lopatin4, Hassan Lyamani1,2, Benjamin Torres4,5, Juan L. Guerrero-Rascado1,2, David Fuertes5, Oleg Dubovik4, Anatoli Chaikovsky6, Francisco J. Olmo1,2, Marc Mallet3, and Lucas Alados-Arboledas1,2 1Department of Applied Physics, University of Granada, 18071 Granada, Spain
2Andalusian Institute for Earth System Research (IISTA-CEAMA), University of Granada, Autonomous Government of Andalusia, 18006 Granada, Spain
3CNRM, Centre National de la Recherche Météorologique (UMR3589, CNRS, Météo-France), Toulouse, France
4Laboratoire d'Optique Atmosphérique, Université de Lille 1, Villeneuve d'Ascq, France
5GRASP-SAS, Remote sensing developments, LOA/Université Lille-1, Villeneuve d'Ascq, France
6Institute of Physics, National Academy of Science, Minsk, Belarus
Abstract. In this study, vertical profiles and column-integrated aerosol properties retrieved by the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) algorithm are evaluated with in situ airborne measurements made during the ChArMEx-ADRIMED field campaign in summer 2013. In the framework of this campaign, two different flights took place over Granada (Spain) during a desert dust episode on 16 and 17 June. The GRASP algorithm, which combines lidar and sun–sky photometer data measured at Granada, was used to retrieve aerosol properties. Two sun-photometer datasets are used: one co-located with the lidar system and the other in the Cerro Poyos station, approximately 1200 m higher than the lidar system but at a short horizontal distance.

Column-integrated aerosol microphysical properties retrieved by GRASP are compared with AERONET products showing a good agreement. Differences between GRASP retrievals and airborne extinction profiles are in the range of 15 to 30 %, depending on the instrument on board the aircraft used as reference. On 16 June, a case where the dust layer was coupled to the aerosol layer close to surface, the total volume concentration differences between in situ data and GRASP retrieval are 15 and 36 % for Granada and Cerro Poyos retrievals, respectively. In contrast, on 17 June the dust layer was decoupled from the aerosol layer close to the surface, and the differences are around 17 % for both retrievals. In general, all the discrepancies found are within the uncertainly limits, showing the robustness and reliability of the GRASP algorithm. However, the better agreement found for the Cerro Poyos retrieval with the aircraft data and the vertical homogeneity of certain properties retrieved with GRASP, such as the scattering Ångström exponent, for cases with aerosol layers characterized by different aerosol types, shows that uncertainties in the vertical distribution of the aerosol properties have to be considered.

The comparison presented here between GRASP and other algorithms (i.e. AERONET and LIRIC) and with airborne in situ measurements shows the potential to retrieve the optical and microphysical profiles of the atmospheric aerosol properties. Also, the advantage of GRASP versus LIRIC is that GRASP does not assume the results of the AERONET inversion as a starting point.


Citation: Benavent-Oltra, J. A., Román, R., Granados-Muñoz, M. J., Pérez-Ramírez, D., Ortiz-Amezcua, P., Denjean, C., Lopatin, A., Lyamani, H., Torres, B., Guerrero-Rascado, J. L., Fuertes, D., Dubovik, O., Chaikovsky, A., Olmo, F. J., Mallet, M., and Alados-Arboledas, L.: Comparative assessment of GRASP algorithm for a dust event over Granada (Spain) during ChArMEx-ADRIMED 2013 campaign, Atmos. Meas. Tech., 10, 4439-4457, https://doi.org/10.5194/amt-10-4439-2017, 2017.
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In this study, vertical profiles and column integrated aerosol properties retrieved by GRASP (Generalized Retrieval of Atmosphere and Surface Properties) algorithm are evaluated with in situ airborne measurements made during the ChArMEx-ADRIMED field campaign in summer 2013. Differences between GRASP retrievals and airborne extinction profiles are in the range of 15 to 30 %. Also, the total volume concentration differences between in situ data and GRASP retrieval ranges from 15 to 36 %.
In this study, vertical profiles and column integrated aerosol properties retrieved by GRASP...
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