A new Profiling Optical Particle Counter to study stratospheric aerosols

Abstract. Stratospheric aerosols play key roles in the radiative and chemical balance of the atmosphere, especially after volcanic and wildfire activities. The sources of stratospheric aerosols have become more complex over the last decade through the influence of Asian pollution, rocket and satellite debris, which could be further enhanced with the potential use of stratospheric aerosol injection under solar radiation management. Knowing stratospheric aerosol size distribution is a fundamental step toward calculating and evaluating their radiative, chemical and climate impacts and validating and/or constraining satellite observations.

We describe here the adaptation of the new lightweight, medium-cost Profiling Optical Particle Counters (POPC) for weather balloon applications. Over the past 8 years, the POPC design and capabilities evolved from a handheld version with 6 channels (POPC-06) to a compact 500g-version with 30 channels measuring aerosol optical diameters between 0.3 to 10 µm. POPC-30 aerosol concentration for d >0.3 µm.  is shown to be within 20% of the Portable Optical Particle Spectrometer (POPS), correlates near 0.97 with the COmpact Backscatter AerosoL Detector (COBALD) and lies within 50% of the extinction coefficients retrieved from highly accurate solar occultation measurements from the Stratospheric Aerosol and Gas Experiment (SAGE III/ISS). With 87 flights since 2018, POPC demonstrated its capabilities to detect volcanic plumes after the 2019 Raikoke, 2019 Ambae, 2021 La Soufriere, 2022 Hunga and 2024 Ruang eruptions and was deployed rapidly to intersect pyroCb smoke plumes in the Northern Hemisphere. The instrument is currently launched by several universities and research institutes in Brazil, India, France and the US as a part of the Balloon Network for stratospheric aerosol Observations (BalNeO) complementing other measurement networks. POPC data set is publicly available to the research community for various applications ranging from boundary layer aerosols to free tropospheric and stratospheric aerosol microphysics.