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The zodiacal light is a night-glow mostly visible along the plane of the ecliptic. It represents the background radiation associated with solar light scattered by the tenuous flattened interplanetary cloud of dust particles surrounding the Sun and the planets. It is an interesting subject of study, as the source of the micrometeoroids falling on Earth, as a link to the activity of the small bodies of the Solar System, but also as a foreground that veils the low brightness extrasolar astronomical light sources. In this review, we summarize the zodiacal light observations that have been done from the ground and from space in brightness and polarization at various wavelength ranges. Local properties of the interplanetary dust particles in some given locations can be retrieved from the inversion of the zodiacal light integrated along the light-of-sight. We show that the current community consensus favors that the majority of the interplanetary dust particles detected at 1 au originate from the activity of comets. Our current understanding of the interplanetary dust particles properties is then discussed in the context of the recent results from the Rosetta rendezvous space mission with comet 67P/Churyumov-Gerasimenko., Accepted for publication in Planetary and Space Science

After 43 years of inactivity, the Calbuco volcano, which is located in the southern part of Chile, erupted on 22 April 2015. The space-time evolutions (distribution and transport) of its aerosol plume are investigated by combining satellite (CALIOP, IASI, OMPS), in situ aerosol counting (LOAC OPC) and lidar observations, and the MIMOSA advection model. The Calbuco aerosol plume reached the Indian Ocean 1 week after the eruption. Over the Reunion Island site (21 S, 55.5 E), the aerosol signal was unambiguously enhanced in comparison with "background" conditions, with a volcanic aerosol layer extending from 18 to 21 km during the May-July period. All the data reveal an increase by a factor of 2 in the SAOD (stratospheric aerosol optical depth) with respect to values observed before the eruption. The aerosol mass e-folding time is approximately 90 days, which is rather close to the value (80 days) reported for the Sarychev eruption. Microphysical measurements obtained before, during, and after the eruption reflecting the impact of the Calbuco eruption on the lower stratospheric aerosol content have been analyzed over the Reunion Island site. During the passage of the plume, the volcanic aerosol was characterized by an effective radius of 0.160.02 μm with a unimodal size distribution for particles above 0.2 μm in diameter. Particle concentrations for sizes larger than 1 μm are too low to be properly detected by the LOAC OPC. The aerosol number concentration was 20 times higher that observed before and 1 year after the eruption. According to OMPS and lidar observations, a tendency toward conditions before the eruption was observed by April 2016. The volcanic aerosol plume is advected eastward in the Southern Hemisphere and its latitudinal extent is clearly bounded by the subtropical barrier and the polar vortex. The transient behavior of the aerosol layers observed above Reunion Island between May and July 2015 reflects an inhomogeneous spatio-temporal distribution of the plume, which is controlled by the localization of these dynamical barriers., SCOPUS: ar.j, info:eu-repo/semantics/published

International audience; After 43 years of inactivity, the Calbuco volcano which is located in the southern part of Chile erupted on 22 April 2015. The space-time evolutions (distribution and transport) of its aerosol plume are investigated by combining satellite (CALIOP, IASI, OMPS), in situ aerosol counting (LOAC OPC) and lidar observations, and the MIMOSA advection model. The Calbuco aerosol plume reached the Indian Ocean 1 week after the eruption. Over the Reunion Island site (21° S; 55.5° E), the aerosol signal was unambiguously enhanced in comparison with "background" conditions with a volcanic aerosol layer extending from 18 km to 21 km during the May–July period. All the data reveal an increase by a factor of ~ 2 in the SAOD (Stratospheric Aerosol Optical Depth) with respect to values observed before the eruption. The aerosol e-folding time is approximately 90 days. Microphysical measurements obtained before, during and after the eruption reflecting the impact of the Calbuco eruption on the lower stratospheric aerosol content have been analyzed over Reunion site. During the passage of the plume, the volcanic aerosol was characterized by an effective radius of 0.16 ± 0.02 µm with an unimodal lognormal size distribution and the aerosol number concentration appears 20 times higher than before and one year after the eruption. A tendency toward "background" conditions has been observed about one year after the eruption, by April 2016. The volcanic aerosol plume is advected eastward in the Southern Hemisphere and its latitudinal extent is clearly bounded by the subtropical barrier and the polar vortex. The transient behavior of the aerosol layers observed above Reunion Island between May and July 2015 reflects an inhomogeneous geographical distribution of the plume which is controlled by the latitudinal motion of these dynamical barriers.

The study of the stratospheric aerosols is important to our understanding of the terrestrial radiative budget. Our current comprehension of the different types of stratospheric particles and their spatial and temporal distribution is incomplete. In the present study, we try to show that measuring particle concentrations by the means of a new balloon-borne miniature particle counter, the LOAC, may allow us to determine the local variability in stratospheric aerosols in the size range 0.2 – 100 μm in diameter. In that respect, the PhD thesis consists of a first phase of a more accurate characterisation of the LOAC’s performances under balloon-borne measurement. A second phase consists of comparative analysis of stratospheric aerosol content based on a LOAC dataset obtained during a continuous campaign of balloon launches in France, along with some occasional flights abroad under particular circumstances (volcanic eruption, monsoon). Thus we show that the LOAC has a detection limit that restricts the measurement of submicronic particles in volcanic quiescent periods for concentrations lower than typically 1 particle per cm3. In its current version, the LOAC allows us to characterise aerosols in volcanic plumes in the troposphere and lower stratosphere. And, further, we propose directions concerning possible calibration and analysis strategies for the future data from the next generation of the LOAC currently in development., L’étude des aérosols stratosphériques est importante pour comprendre le bilan radiatif terrestre. A l’heure actuelle, notre représentation des différents types de particules stratosphériques et leurs répartitions spatiale et temporelle n’est pas complète. Au cours de cette thèse, nous tentons de montrer que la mesure de la concentration en particules sous ballon météorologique au moyen d’un nouveau mini compteur de particules, le LOAC, pourrait permettre de rendre compte de la possible variabilité locale du contenu en aérosols stratosphériques dans la gamme de taille 0,2 à 100 μm en diamètre. La première partie de ce travail consiste à caractériser plus précisément les performances du LOAC sous ballon météorologique appliqué à la mesure en stratosphère. La seconde partie propose une analyse comparée du contenu en aérosols stratosphériques obtenu par LOAC, à partir de lâchers de ballons en France régulièrement depuis 3 ans et plus ponctuellement à l’étranger dans des situations particulières (volcan, mousson), et par d’autres types de données (Observations spatiales, lidar sol et simulation globale). Nous montrons alors que l’instrument possède une limite de détection rendant difficile la mesure des particules submicroniques lors de période de fond en moyenne stratosphère pour des concentrations de l’ordre d’une particule par cm3. Dans sa version actuelle, le LOAC permet de documenter les panaches volcaniques en troposphère ainsi qu’en basse stratosphère. En perspective, nous proposons des directions pour la calibration et l’analyse des futures données d’une nouvelle génération de l’instrument en développement.

International audience; We present findings from a measurement campaign that deployed a range of in-situ real-time atmospheric measurement techniques to characterise aerosols and gases in Mt Etna plume in October 2013. The LOAC (Light Optical Aerosol Counter) instrument for size-resolved particle measurements was deployed alongside two Multi-Gas instruments (measuring SO 2 , H2S, HCl, CO 2) and an ozone sensor. Measurements were performed at the summit craters (in cloudy-and non-cloudy conditions) and in grounding downwind plume on the volcano flank. These high frequency measurements (acid gases: 1 to 0.1 Hz, aerosol: 0.1 Hz) provide a detailed in-situ dataset for time-resolved plume characterisation and volcano monitoring. The LOAC measurement of sized-resolved aerosol (over a 0.2 to 50 µm particle diameter range) alongside SO 2 (10's ppbv to 10's ppmv) provides a valuable dataset for determining the volcanic aerosol volume and surface area to SO 2 ratios. These parameters are presently poorly defined but are important for atmospheric models of the reactive halogen chemistry that occurs on volcanic aerosol surfaces to convert volcanic HBr into reactive bromine, including BrO. The LOAC's patented optical design can also provide insights into particle properties. The two Multi-Gas SO 2 time-series show good agreement, detecting co-varying plume fluctuations in the downwind plume, which also correlate with the LOAC total aerosol volume time-series. An estimate of HCl/SO 2 in Etna emissions was made by Multi-Gas electrochemical sensor, using a novel design to limit absorption/desorption effects and low-noise electronics for improved resolution. The detection of volcanic HCl by electrochemical sensor brings new possibilities for Multi-Gas monitoring of volcanic halogen emissions. Electrochemical sensor response times are not instantaneous, particularly for sticky gases such as HCl (T90 ∼min), but also even for " fast " response (T90 ∼ 10 to 30 s) sensors such as SO 2 and H2S. However, in a volcanic plume environment, Multi-Gas instruments are exposed to very rapidly fluctuating gas concentrations due to turbulent plume eddies. The combination of these effects can introduce measurement errors, emphasizing a need for sensor response modelling approaches for accurate determination of gas ratios from Multi-Gas instruments.

This paper describes the aerosol measurement setup and results obtained during the BEXUS18 (Balloon-borne Experiments for University Students) stratospheric balloon within the A5-Unibo (Advanced Atmospheric Aerosol Acquisition and Analysis) experiment performed on 10 October 2014 in northern Sweden (Kiruna). The experimental setup was designed and developed by the University of Bologna with the aim of collecting and analyzing vertical profiles of atmospheric ions and particles together with atmospheric parameters (temperature, relative humidity, and pressure) all along the stratospheric ascent of the BEXUS18 stratospheric balloon. Particle size distributions were measured with the MeteoModem Light Optical Aerosol Counter (LOAC) and air ion density was measured with a set of two commercial and portable ion counters. Though the experimental setup was based upon relatively low-cost and light-weight sensors, vertical profiles of all the parameters up to an altitude of about 27 km were successfully collected. The results obtained are useful for elucidating the relationships between aerosols and charged particles between ground level and the stratosphere, with great potential in collecting and adding useful information in this field, also in the stratosphere where such measurements are rare. In particular, the equipment detected coherent vertical profiles for particles and ions, with a particularly strong correlation between negative ions and fine particles, possibly resulting from proposed associations between cosmic rays and ions as previously suggested. In addition, the detection of charged aerosols in the stratosphere is in agreement with the results obtained by a previous flight and with simulations conducted with a stratospheric ion–aerosol model. However, further measurements under stratospheric balloon flights equipped with a similar setup are needed to reach general conclusions about such important issues.