Aerosol–cloud interactions over the Southern Ocean

• Main Author: Hartery, Sean
• Format: Other/Unknown Material
• Language: English
• Published: University of Canterbury 2021
• Subjects: New Zealand; Ross Sea; Southern Ocean
• Online Access: https://hdl.handle.net/10092/101713; https://doi.org/10.26021/10766

In this work, connections between the abundance of sub-micrometer particulate within the marine boundary layer and optical properties of low-level marine stratus over the Southern Ocean are explored. Global climate models (GCMs) currently predict that much more shortwave radiation is entering the Earth system over the Southern Ocean than satellite- borne radiometers observe. This undermines long-term climate projections in the wider region, leading to greater uncertainty about our climate future. The central hypothesis of this thesis is thus: as the Southern Ocean is a region with near-total cloud cover, and as clouds are opaque to shortwave radiation, and as the abundance of boundary layer particulate available to nascent clouds is known to strongly influence the opacity of those clouds, then radiative biases within GCMs are fundamentally related to the abundance of boundary layer particulate. The goals of this thesis are thus two-fold. First, to quantify whether GCMs accurately represent the abundance and types of particles present within the Southern Ocean boundary layer; and if not, use new observations to constrain existing parameterizations predicting their generation. Second, to quantify how sensitive Southern Ocean clouds are to variations in the abundance of such particles. Central to this examination is a new record of measurements collected within the Southern Ocean boundary layer. In February of 2018, scientific instruments were installed on the R/V Tangaroa for a voyage to the Ross Sea. The voyage departed and returned to Wellington, New Zealand, providing 40 days of continuous in situ observations within the marine boundary layer. This included measurements of the abundance of suspended particulate by an optical particle counter, a differential mobility analyzer and a cloud condensation nuclei counter; discrete samples of ambient particulate collected on filters; attenuated back-scattered light from the boundary layer measured by a ceilometer, and several meteorological variables measured by ...