Interpretation of lidar depolarization measurements of the Pinatubo stratospheric aerosol layer during EASOE

• Published in: Geophysical Research Letters
• Main Authors: Flesia, C., Mugnai, A., EMERY, Y., Godin, Sophie, Schoulepnikoff, L. de, Mitev, Valentin
• Other Authors: Ecole Polytechnique Fédérale de Lausanne (EPFL), Istituto di Scienze dell'Atmosfera e del Clima (ISAC), Consiglio Nazionale delle Ricerche Roma (CNR), Service d'aéronomie (SA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire Cantonal de Neuchâtel (OCN)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1994
• Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Arctic
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03083132; https://hal-insu.archives-ouvertes.fr/insu-03083132/document; https://hal-insu.archives-ouvertes.fr/insu-03083132/file/ark%20_67375_WNG-PQJH0B5S-0.pdf; https://doi.org/10.1029/93GL02897

International audience During the EASOE campaign in the Arctic, all lidar measurements showed total depolarization values for the Pinatubo stratospheric aerosol layer varying between 2% and 4%. If multiple scattering is negligible, the radiation backscattered by a polydispersion of spheres has the same polarization as the incident light. There is always some depolarization of a lidar return because of the anisotropy of the polarizability of the air molecules, but depolarization in the signal returned from aerosols indicates the presence of non‐spherical particles. In this paper, we utilize scattering calculations for non‐spherical particles to explore interpretations of lidar signals returned by Pinatubo aerosols. Taking into account several particle shapes and lognormal size distributions, calculations show that only slightly‐to‐moderate deformed spheres with equivalent‐mean‐radius less then 0.2 µm yield depolarization values in the range given by the lidar measurements, if such particles form a substantial fraction of the population. The implications of particle non‐sphericity on the retrieval of the aerosol size distribution are discussed.