Tropospheric and stratospheric cloud and dynamics research at the Australian Antarctic Division

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• Simon Alexander, Australia Antarctic Division, Hobart, Australia
• Thursday 30 January 2014, 14:00-15:00
• British Antarctic Survey, Room 307.

If you have a question about this talk, please contact Victoria Hamilton-Morris.

The Davis, Antarctica (69S, 78E) atmospheric observatory contains numerous remote sensing instruments, including a Rayleigh lidar and a VHF wind-profiling radar. Ozonesondes and twice-daily radiosondes are also launched from Davis. In this seminar I will focus on some of the science conducted using data which we have collected in the troposphere and stratosphere.

Little is known about Antarctic clouds compared to other regions, yet they are crucial for a correct understanding of the ice sheet mass balance and surface radiative balance. The incorrect representation of Southern Ocean clouds creates uncertainties in future projections of the Antarctic via atmospheric transport processes. Measuring various cloud properties over seasonal time-scales will provide parameters for climate and forecast model evaluation. The poor quality of gravity wave drag parameterizations limits models’ ability to accurately represent stratospheric ozone change and its consequences for the weather and climate. Observations we are making at Davis seek to improve this aspect of models too, by, as a first step, quantifying and understanding wave sources in the southern high latitudes.

For the last few years, a Rayleigh lidar has made campaign-based observations of upper tropospheric cirrus clouds and polar stratospheric clouds. During spring 2012, a new polarization system was deployed to Davis, allowing for the determination of cloud phase. High-resolution observations of polar stratospheric clouds demonstrate the presence of high frequency gravity waves throughout the cloud decks: I will discuss PSC and tropospheric cloud results from the Davis lidar and the CALIPSO satellite lidar (from the entire Antarctic). I will provide an overview of a planned field experiment to quantify key tropospheric cloud and surface radiation properties in the Southern Ocean and East Antarctic via the deployment of several remote-sensing instruments to both Davis and Macquarie Island (54S, 159E) for a year-long campaign at each location.

The VHF radar at Davis provides wind profiles in the troposphere and is currently being upgraded to increase the altitude coverage into the lower stratosphere. Using these observations and reanalyses data, I will show both the seasonal cycle of gravity wave activity and a case study of orographic and non-orographic gravity waves observed in the troposphere above Davis. This case study will demonstrate the interaction of katabatic winds and wind from transient synoptic-scale depressions passing to the north of Davis with the topography to generate the gravity waves seen above Davis with the radar.

This talk is part of the British Antarctic Survey series.

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