Abstract. Raman lidar data obtained over a one year period has been analyzed in relation to aerosol layers in the free troposphere over the Highveld in South Africa. In total, 375 layers were observed above the boundary layer during the period 30 January 2010–31 January 2011. The seasonal behavior of aerosol layer geometrical characteristics, as well as intensive and extensive optical properties were studied. The highest center heights of free tropospheric layers were observed during the South African spring (2520 ± 970 m a.g.l.). The geometrical layer depth was found to be maximum during spring, while it did not show any significant difference for the rest of the seasons. The variability of the analyzed intensive and extensive optical properties was high during all seasons. This was attributed to the mixing state of aerosols and the different transport paths of the aerosol layers. Layers were observed at a mean altitude of 2100 ± 1000 m a.g.l. with an average lidar ratio of 67 ± 25 sr (mean value with one standard deviation) at 355 nm and a mean extinction-related Ångström exponent of 1.9 ± 0.8 between 355 and 532 \\unit{nm} during the period under study. During southern hemispheric spring, the biomass burning activity is clearly reflected in the optical properties of the observed free tropospheric layers. Specifically, lidar ratios at 355 nm were 57 ± 20 sr , 65 ± 23 sr, 59 ± 22 sr and 89 ± 21 sr during summer (December–February), winter (June–August), autumn (March–May) and spring (September–November), respectively. The extinction-related Ångström exponents between 355 and 532 nm measured during summer, winter, autumn and spring were 2.4 ± 0.9, 1.8 ± 0.6, 1.8 ± 0.9 and 1.8 ± 0.6, respectively. The mean columnar aerosol optical depth (AOD) obtained from lidar measurements was found to be 0.46 ± 0.35 at 355 nm and 0.25 ± 0.2 at 532 nm.The contribution of free tropospheric aerosols on the AOD had a wide range of values with a mean contribution of 46%.

Very little research on Søderberg electrodes has been published in the journal peer reviewed public domain. The main aim of this work is to characterise a Søderberg electrode that was cut off approximately 0.5 m below the contacts shoes of a submerged arc furnace. Additionally, the characterisation data can be used to verify if Søderberg electrode models accurately predict important electrode characteristics. The operational history (slipping, current, and paste levels) proved that the case study electrode was a representative specimen. The characterisation results indicated no significant electrical resistivity, degree of graphitisation (DOG), and bulk density changes from 0.7 to 2.7 m on the non-delta side (outward facing), while these characteristics changed relatively significantly on the delta side (inward facing) of the electrode. The area where the submerged arc would mostly like jump off the electrode had the lowest resistivity, as well as highest DOG and bulk density. No significant difference in porosity as a function of length below the contact shoes were observed; however, slight increases occurred near the perimeters. It was postulated that oxidation of carbon resulted in increased pore volumes near the electrode perimeter. No significant difference in compressive breaking strength was observed over the electrode area investigated.

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