Separation of the optical and mass features of particle components in different aerosol mixtures by using POLIPHON retrievals in synergy with continuous polarized Micro-Pulse Lidar (P-MPL) measurements
Authors: Córdoba-Jabonero Carmen , Sicard Michaël , Ansmann Albert , del Águila Ana , Baars Holger 
Published: February 2018

Abstract. The application of the POLIPHON (POlarization-LIdar PHOtometer Networking) method in synergy with continuous 24/7 polarized Micro-Pulse Lidar (P-MPL) measurements to derive the vertical separation of two/three particle components in different aerosol mixtures, and the retrieval of their particular optical properties, is presented for the first time. The procedure of extinction-to-mass conversion, together with an analysis of the Mass Extinction Efficiency (MEE) parameter, is described, and the relative mass contribution of each aerosol component is also derived in a further step. The general POLIPHON algorithm is based on the specific particle linear depolarization ratio given for different types of aerosols, and can be run in either 1-step (POL-1) or 2 steps (POL-2) versions in dependence on the either 2- or 3-component separation. In order to illustrate this procedure aerosol mixing cases observed over Barcelona (NE Spain) are selected: a dust event occurred on 5 July 2016; smoke plumes detected on 23 May 2016; and a pollination episode observed on 23 March 2016. In particular, the 3-component separation is just applied for the dust case: a combined POL-1 with POL-2 procedure (POL-1/2) is used, and additionally the dust fine contribution to the total fine mode (dust fine plus non-dusty aerosols) is estimated. The high dust impact occurred in the first part of the day yields a mean mass loading of 0.6 &amp;pm; 0.1 g m−2 due to the prevalence of Saharan dust coarse particles in comparison with that obtained for the second part of the day, just a 34 % out of previous value, showing a rather weak dust incidence. In the smoke case, the arrival of fine biomass burning particles is detected at altitudes as high as 7 km height. The smoke signature, also mixed with larger less depolarizing non-smoke aerosols, is observed along the day in dependence on the singular air masses origin with height, from either North America fires or the Arctic area, as reported by HYSPLIT backtrajectory analysis. The particle linear depolarization ratio for smoke shows values in the 0.10–0.15 range, even higher at given times, and the daily mean smoke mass loading is 0.017 &amp;pm; 0.008 g m−2, around 3 % out of that found for the dusty event. Pollen particles are detected up to 1.5 km height from 10:00 UTC on during an intense pollination event with a particle linear depolarization ratio ranging between 0.10 and 0.15. The maximal mass loading of Platanus pollen particles is 0.011 &amp;pm; 0.003 g m−2, representing around 2 % out of the dust loading during the higher dust incidence. Regarding the MEE derived for each aerosol component, their values are in agreement with other referenced in the literature for those specific aerosol types examined in this work: 0.5 &amp;pm; 0.1 m2 g−1 and 1.7 &amp;pm; 0.2 m2 g−1 are found for dust coarse and fine particles, respectively; 4.5 &amp;pm; 1.4 m2 g−1 is derived for smoke, and 2.4 &amp;pm; 0.5 m2 g−1 for non-smoke aerosols with Arctic origin (a MEE value close to that reported for Arctic aerosols: 2.17 m2 g−1, as supposed larger aerosols than those biomass burning particles); and a MEE of 2.4 &amp;pm; 0.8 m2 g−1 is obtained for pollen particles, though it can reach higher/lower values depending on a predominant smaller/larger size of the pollen grains. Results reveal the high potential of the P-MPL system, a simple polarization-sensitive elastic backscatter lidar working in a 24/7 operation mode, to retrieve the relative optical and mass contributions of each aerosol component along all the day, reflecting the daily variability of their properties. Moreover, the method has the advantage to be relatively easily applicable also to spaceborne lidars with an equivalent configuration such as the ongoing Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard NASA/CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), and the forthcoming Atmospheric Lidar (ATLID) onboard ESA/EarthCARE mission.