Southern Ocean Aerosol Optical Depth - instrument comparison and Maine Aerosol Network Validation

A series of atmospheric instruments were deployed aboard the research vessel RV Investigator for a 42-day campaign in 2018 to quantify aerosol optical depth and the properties associated with aerosol in the Southern Ocean marine boundary layer between Australia and Antarctica. The optical depth measurements collected via Microtops sun photometers and LiDAR were analysed for data compatibility to increase the dataset. It was found that aerosol optical depth that was derived from the day-time LiDAR measurements were too noisy to be compatible with the known optical depth measurements. However, an analysis exploring optical depth measurements derived from night-time data indicated moderate compatibility with the known measurements and could be analysed in future studies. Three cases studies, two high aerosol optical depth periods (means of 0.22 and 0.198) and one low period (mean of 0.061), were identified for analyses from the data collected by the Microtops II sun photometer. Data reviewed from LiDAR including cloud type and attenuated backscatter alongside backward trajectory wind path models showed physical mechanisms that were consistent with sea spray aerosol production for the two high periods. The third period which experienced low optical depth and was the closest period to Antarctica indicated sea ice and continental influence, reducing the aerosol formation