Davis Medium Frequency Middle Atmosphere Radar Winds

Full description

This dataset contains wind speed and direction in the middle atmosphere above Davis, Antarctica. The radar runs continuously. Data are collected and stored every two minutes (excluding downtime for maintenance) for heights in the approximate range 50km to 110km at 2km intervals. Analysis of the source data yields parameters describing the strength and character of the radar echo and, when certain acceptance criteria are met, the wind speed. The requirement to meet acceptance criteria results in a data rate that may be less than the sampling rate.

Data collection began in 1994 and is ongoing.

Changes to the polarisation of the transmitted radar pulse are used to maximise the range over which winds can be obtained, using the differing reflection and absorption characteristics of the ordinary and extraordinary modes. These have the potential to yield measures of electron density over the sampled height range. A combination of technical difficulties and unknown issues have meant that these data have not yielded results that are considered reliable.

The data set is standalone. MFSA stands for Medium Frequency Spaced Array. This is in reference to the transmitted frequency and the antenna configuration needed for Full Correlation Analysis (FCA).

Project History:
The operation of the MFSA radar has supported a number of Antarctic Science Research projects. These include:
Project 674 – ‘Dynamical coupling in the Antarctic middle atmosphere’. 1993/94 to 2011/12
Project 4025 – ‘Gravity wave drag parameterization in climate models’. 2012/13 to 2016/17
Project 4445 – ‘High-latitude gravity wave processes and their parameterization in climate models’ 2017/18 to 2020/21
Further details of the outcomes of these projects can be found on the Antarctic Division website www.aad.gov.au. The data have also contributed to Australian and international research activities beyond these projects. Similar radars are/have been operated by other countries at Antarctic stations including Syowa (Japan), Rothera (UK), McMurdo (USA) and Scott Base (NZ).

Technical History:
Summer 1993/94 – New radar equipment and existing equipment previously operating at Mawson station were installed at Davis. Operation and data collection began on 11 April 1994. This mode of operation used 8-bit digitisation of received signals, ongoing gain adjustment and polarization changes between (rather than within) data accumulation cycles.
Summer 2000/2001 – An upgrade to the receiver and digitiser system removed the need for gain adjustment and introduced 12 bit digitisation. Polarisation changes within data accumulation cycles became possible. Operation began on 7 November 2000.
Summer 2003/2004 - Replaced ‘TOMCO’ transmitter with 3rd generation ATRAD transmitter.
Summer 2008/9 – Container laboratory replaced.
Feb 2012 – Transmit antenna replaced. Replacement allows tap changes to improve tuning of antenna impedance.

Lineage

Progress Code: completed

Statement: Data analysis may or may not yield a full set of attributes. Data acceptance rates vary with height. The radar runs continuously (excluding downtime for maintenance and data transfer). Source data consists of digitised and coherently averaged measurements of the in phase and quadrature signal levels for each of the three receiving antennas and for each range that is sampled. The source data are collected for the first 102.4 seconds of each 2 minute interval that the radar is operational. The source data are analysed using Full Correlation Analysis to produce winds and a number of parameters describing the radar echoes. All data are labelled with height and (universal) time. The radar produces an average wind for the region described by the geographical polygon. Adjacent 2 km height samples straddle the ‘width’ of the transmitted pulse and so are not independent samples. Ionospheric disturbances can drastically increase the radio wave absorption in the sampled height range so that no winds are measured or that they are measured at lower altitudes. Such disturbances can last for a day or longer. At times, the analysis yields wind measurements in the lower height ranges (below approximately 60 km) that pass the acceptance criteria but that are spatially and temporally variant is magnitude and direction. These are not thought to be real wind measurements. Instead they are thought to be the effects of ‘sea-ice clutter’ where horizontal radar power leakage is reflected from slowly moving ice. Iceberg traces are sometimes also visible in signal to noise ratio measurements. These forms of data corruption are dominant below the usual range of wind measurements.