Weather and climate models are challenged by uncertainties and biases in simulating Southern Ocean (SO) radiative fluxes that trace to a poor understanding of cloud, aerosol, precipitation and radiative processes, and their interactions. Projects between 2016 and 2018 used in-situ probes, radar, lidar and other instruments to make comprehensive measurements of thermodynamics, surface radiation, cloud, precipitation, aerosol, cloud condensation nuclei (CCN) and ice nucleating particles over the SO cold waters, and in ubiquitous liquid and mixed-phase cloudsnucleating particles over the SO cold waters, and in ubiquitous liquid and mixed-phase clouds common to this pristine environment. Data including soundings were collected from the NSF/NCAR G-V aircraft flying north-south gradients south of Tasmania, at Macquarie Island, and on the RV Investigator and RSV Aurora Australis. Synergistically these data characterize boundary layer and free troposphere environmental properties, and represent the most comprehensive data of this type available south of the oceanic polar front, in the cold sector of SO cyclones, and across seasons.Results show a largely pristine environments with numerous small and few large aerosols above cloud, suggesting new particle formation and limited long-range transport from continents, high variability in CCN and cloud droplet concentrations, and ubiquitous supercooled water in thin, multi-layered clouds, often with small-scale generating cells near cloud top. These observations demonstrate how cloud properties depend on aerosols while highlighting the importance of confirmed low clouds were responsible for radiation biases. The combination of models and observations is examining how aerosols and meteorology couple to control SO water and energy budgets.

[1] Temperature profiles derived from Constellation Observing System for Meteorology, Ionosphere and Climate Global Positioning System Radio Occultation satellite constellation data are used to study equatorial gravity wave potential energy associated with waves having vertical wavelengths of less than 7 km and their interaction with the background quasi-biennial oscillation (QBO) wind. The data are binned into grids of size 20°in longitude and 5°in latitude. Results show evidence of vertically propagating convectively generated gravity waves interacting with the background mean flow. Enhancements in potential energy around the descending 0 m s À1 QBO eastward shear phase line are observed. Equatorially trapped Kelvin waves and Mixed Rossby Gravity Waves with zonal wave numbers s 9 are obtained by bandpass filtering wave number-frequency temperature spectra. Their temporal, spatial and vertical structures, propagation and wave-mean flow interactions are examined with respect to the background mean flow. Equatorial waves observed by COSMIC are compared with those seen in OLR data, with differences discussed.

and 2012 are used to compile a climatology of lower stratosphere inertial gravity wave characteristics. Wavelet analysis extracts single wave packets from the wind and temperature perturbations. Wavelet parameters, combined with linear gravity wave theory, allow for the derivation of a wide range of wave characteristics. Observational filtering associated with this analysis preferentially selects inertial gravity waves with vertical wavelengths less than 2-3 km. The vertical propagation statistics show strong temporal and height variations. The waves propagate close to the horizontal and are strongly advected by the background wind in the wintertime. Notably, around half of the waves observed in the stratosphere above Davis between early May and mid-October propagate downward. This feature is distributed over the observed stratospheric height range. Based on the similarity between the upward and downward propagating waves and on the vertical structure of the nonlinear balance residual in the polar winter stratosphere, it is concluded that a source due to imbalanced flow that is distributed across the winter lower stratosphere best explains the observations. Calculations of kinetic and potential energies and momentum fluxes highlight the potential for variations in results due to different analysis techniques.

Gravity wave activity in the upper stratosphere and lower mesosphere (USLM) is investigated using temperature data retrieved from a Rayleigh lidar at Davis, Antarctica (69°S, 78°E) during the 2007 and 2008 winters. The temporal and height variabilities of waves with ground‐based periods greater than 2 h and vertical wavelengths between 4 km and 20 km are analyzed. Stratospheric gravity wave potential energy per unit mass shows a weaker correlation with stratospheric winds at Davis than that reported in the Arctic. Gravity waves dissipate above 40 km during winter, while there is no dissipation in the autumn mesosphere. A separate analysis of gravity waves with ground‐based periods of 2–6 h revealed lower dissipation in the winter mesosphere. The seasonal cycle of gravity wave activity is evident throughout the USLM, with peak activity observed during winter. The gravity wave potential energy and vertical wavenumber power spectral density at Davis are similar to that recorded at other high‐latitude sites.