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: August 2018

Abstract. The application of the POLIPHON (POlarization-LIdar PHOtometer Networking)
method is presented for the first time in synergy with continuous
24/7 polarized Micro-Pulse Lidar (P-MPL)
measurements to derive the vertical separation of two or three particle
components in different aerosol mixtures, and the retrieval of their
particular optical properties. 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 with dependence on either the
2- or 3-component separation. In order to illustrate this procedure, aerosol
mixing cases observed over Barcelona (NE Spain) are selected: a dust event
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 fine-dust contribution to
the total fine mode (fine dust plus non-dust aerosols) is estimated. The
high dust impact before 12:00 UTC yields a mean mass loading of
0.6±0.1 g m−2 due to the prevalence of Saharan coarse-dust
particles. After that time, the mean mass loading is reduced by two-thirds,
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.
The smoke particles, probably mixed with less depolarizing non-smoke
aerosols, are observed in air masses, having their origin from either North
American fires or the Arctic area, as reported by HYSPLIT back-trajectory
analysis. The particle linear depolarization ratio for smoke shows values in
the 0.10–0.15 range and even higher at given times, and the daily mean smoke
mass loading is 0.017±0.008 g m−2, around 3 % of that found
for the dust event. Pollen particles are detected up to 1.5 km in height from
10:00 UTC 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±0.003 g m−2,
representing around 2 % of the dust loading during the higher dust
incidence. Regarding the MEE derived for each aerosol component, their values
are in agreement with others referenced in the literature for the specific
aerosol types examined in this work: 0.5±0.1 and
1.7±0.2 m2 g−1 are found for coarse and fine dust particles, 4.5±1.4 m2 g−1 is derived for smoke and
2.4±0.5 m2 g−1 for non-smoke aerosols with Arctic origin, and a MEE of 2.4±0.8 m2 g−1 is obtained
for pollen particles, though it can reach higher or lower values depending on
predominantly smaller or larger pollen grain sizes. 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 throughout
the day, reflecting the daily variability of their properties. In fact, this
procedure can be simply implemented in other P-MPLs that also operate within the
worldwide Micro-Pulse Lidar Network (MPLNET), thus extending the aerosol
discrimination at a global scale. Moreover, the method has the advantage of also
being relatively easily applicable to space-borne lidars with an equivalent
configuration such as the ongoing Cloud-Aerosol LIdar with Orthogonal
Polarization (CALIOP) on board NASA CALIPSO (Cloud-Aerosol Lidar and Infrared
Pathfinder Satellite Observation) and the forthcoming Atmospheric
Lidar (ATLID) on board the ESA EarthCARE mission.