Comparison of Coincident Optical Particle Counter and Lidar Measurements of Polar Stratospheric Clouds Above McMurdo (77.85°S, 166.67°E) From 1994 to 1999

Abstract

Polar stratospheric clouds (PSCs), which form in the polar stratosphere during winter and early spring, play an important role in the stratospheric chemistry processes which deplete stratospheric ozone in the Polar Regions (see e.g., Solomon, 1999). The PSC particles provide surfaces on which inactive forms of chlorine are converted into reactive, ozone-destroying forms. In addition, they remove nitrogen compounds that moderate the destructive impact of chlorine. Several particle types are observed in PSCs, both in liquid and solid phase, containing sulfuric acid, nitric acid, and water. All PSC particles form on the underlying sulfuric acid and water (sulfate) aerosol which blankets the stratosphere. These sulfate aerosols form from the condensation of oxidized sulfur which reaches the stratosphere from surface production of OCS and SO 2 and from volcanic outbursts and biomass burning (Kremser et al., 2016; Thomason & Peter, 2006). These stratospheric aerosols then form the condensation sites for PSCs in the polar regions. The microphysical formation processes of PSCs depend on the availability of condensation nuclei, on the temperature and on the number density of water and nitric acid molecules in the gas phase. Detailed discussions of these processes can be found in

A study of Mie scattering modelling for mixed phase Polar Stratospheric Clouds

“…Figure 5 reports the scatterplot of measured vs modelled β A and represent the analogue of figure 4 in Snels et al (2021), where in the present case we have used a larger dataset including Arctic balloon flights, and basically confirms the conclusions reported there. While the agreement between calculations and measurements can be considered satisfactory for β A , it is certainly not so for δ A as can be clearly seen from figure 6 which reports the scatterplot of its measured and modelled values.…”

“…We have studied fifteen coincident measurements by groundbased lidar and balloon-borne Optical Particle Counters (OPC) taken above McMurdo Station, Antarctica between 1994(Snels et al, 2021 and four in situ balloonborne observations taken by laser backscattersonde and OPC during 4 balloon stratospheric flights from Kiruna, Sweden, between 2000and 2002(Weisser et al, 2006. The Antarctic lidar and balloonborne OPC dataset has been extensively discussed in Snels et al (2021) where it has been used to provide empirical relations linking particle Surface Area and Volume densities with the backscatter coefficients. The main characteristics of the instrumentation will be here only briefly recalled.…”

A study of optical scattering modelling for mixed phase Polar Stratospheric Clouds

“…We have analysed fifteen measurements of PSC optical parameters observed by a groundbased lidar, coincident with microphysical observations acquired by a balloon-borne Optical Particle Counter (OPC). These observations were taken above McMurdo Station, Antarctica, between 1994(Snels et al, 2021. In addition we analysed four in situ balloonborne observations carried out by a laser backscattersonde and an OPC during 4 stratospheric balloon flights from Kiruna, Sweden, between 2000and 2002(Weisser et al, 2006.…”

“…In addition we analysed four in situ balloonborne observations carried out by a laser backscattersonde and an OPC during 4 stratospheric balloon flights from Kiruna, Sweden, between 2000and 2002(Weisser et al, 2006. The Antarctic lidar and balloonborne OPC dataset has been extensively discussed in Snels et al (2021) where it has been used to provide empirical relations linking particle Surface Area and Volume densities with the backscatter coefficients. The main characteristics of the instrumentation will be here only briefly recalled.…”

“…The speed of computation it offers is advantageous when used for statistical or climatological studies (Pitts et al, 2009(Pitts et al, , 2013, or when optical properties less dependent on the assumption of sphericity have to be calculated, as is in the case of extinction (David et al, 2012;Daerden et al, 2007). In PSC studies, Mie theory was also sometimes used to simulate aspheric particulate backscattering, employing corrections that take into account its reduction due to the asphericity of the scatterers (Snels et al, 2021;Cairo et al, 2022). However, the Mie theory cannot produce depolarized backscattering and attempts with simple empirical models to use it to mimic depolarization from aspherical particles does a very poor job in reproducing the measured depolarization (Cairo et al, 2022).…”