Origins and Spatial Distribution of Non-Pure Sulfate Particles (NSPs) in the Stratosphere Detected by the Balloon-Borne Light Optical Aerosols Counter (LOAC)

Abstract

While water and sulfuric acid droplets are the main component of stratospheric aerosols, measurements performed for about 30 years have shown that non-sulfate particles (NSPs) are also present. Such particles, released from the Earth mainly through volcanic eruptions, pollution or biomass burning, or coming from space, present a wide variety of compositions, sizes, and shapes. To better understand the origin of NSPs, we have performed measurements with the Light Optical Aerosol Counter (LOAC) during 151 flights under weather balloons in the 2013–2019 period reaching altitudes up to 35 km. Coupled with previous counting measurements conducted over the 2004–2011 period, the LOAC measurements indicate the presence of stratospheric layers of enhanced concentrations associated with NSPs, with a bimodal vertical repartition ranging between 17 and 30 km altitude. Such enhancements are not correlated with permanent meteor shower events. They may be linked to dynamical and photophoretic effects lifting and sustaining particles coming from the Earth. Besides, large particles, up to several tens of μm, were detected and present decreasing concentrations with increasing altitudes. All these particles can originate from Earth but also from meteoroid disintegrations and from the interplanetary dust cloud and comets.

Aerosol Characterization of the Stratospheric Plume From the Volcanic Eruption at Hunga Tonga 15 January 2022

“…Observed number concentrations for the two peak altitudes at 22 and 25 km on 23 January exceed aerosol background concentrations at 20 km altitude by a factor of 10-40. The observed size distribution of the background aerosol is comparable to background conditions observed during previous LOAC flights (e.g., Renard, Berthet, et al (2020)). Size distribution observations within the aerosol plume are in the same order of those observed in other volcanic plumes (e.g., after the Calbuco eruption in 2015, Bègue et al (2017)).…”

Variability of the Aerosol Content in the Tropical Lower Stratosphere from 2013 to 2019: Evidence of Volcanic Eruption Impacts

“…Good agreement is observed between the model and the OPC, except above 25 km where the measured increase is not reproduced by the model. Such a high altitude feature has been occasionally observed and has not been yet clearly attributed to a specific phenomenon [6,96]. We note that the WACCM-OPC discrepancies on the concentration values do not match the WACCM-OMPS SAOD differences showing better agreement on 19 May than on 19 August 2015 (Figure 4).…”

“…Sulphate aerosol in the stratosphere is expected to be mainly controlled by natural emissions of carbonyl sulfide (OCS) and sulphur dioxide (SO2), although anthropogenic contributions remain debated [3,4]. The subsequent formation of droplets composed of sulphuric acid and water through binary homogeneous nucleation, with an additional supply of smaller amounts of meteoritic and other non-sulphate material [5,6], is responsible for the presence of a ubiquitous stratospheric aerosol layer. The largest source of sulphate aerosols is due to explosive volcanic eruptions which inject large quantities of SO2 directly into the stratosphere.…”

Evolution of air quality in Morocco before and during the COVID-19 pandemic; comparative study

“…The capital is Rabat and the largest city is Casablanca. Morocco spans an area of 710 850 km 2 and has a population of over 36 471 769 inhabitants (2019) [10]. This assessment, based on the analysis of data from air quality monitoring stations, before, during and after the state of health emergency [11].…”