A Meteor Radar for Measuring Mesospheric and Lower Thermospheric Winds and Temperatures at Davis Station

Brief description

Metadata record for data from ASAC Project 2529
See the link below for public details on this project.

Public
A meteor radar will be installed at Davis Station to measure temperatures and wind velocities in the 80 to 100 km region of the atmosphere. It will do this by tracking the trail of ionised gas produced by meteors as they pass through this region. These trails are blown along by the winds after they are formed, and so act as tracers of the wind, before being dispersed. Understanding the region is important, because it is believed to be providing indications of climate change.

Project objectives:
The upgraded meteor radar will complement the MF radar, the MST radar, the lidar, and the photometer operating at Davis Station. The increased power will provide a higher meteor count rate that will allow the vertical temperature structure of the tidal motions to be investigated [Hocking and Hocking, 2002]. There will be no routine summer measurements of MLT temperature at high southern latitudes apart from those that will be provided by the meteor radar. This is a key parameter in understanding the PMSE. In addition, the increased count rate and the new transmit configuration will allow an investigation of the utility of using high powered meteor radars to measure gravity wave momentum fluxes. In the winter months, the meteor radar will provide estimates of the mean and fluctuating temperatures in the 80 to 100 km height region that complement the T-OH measurements that when combined will allow the density and pressure of the region to be inferred. The meteor radar will also provide wind measurements that complement those derived from the MF radar.

Taken from the 2008-2009 Progress Report:
Progress against objectives:
The Davis system has operated in interleaved meteor mode during the entire season. Winds and mesospheric temperatures are available. The new high power transmit antenna developed and trialled on the sister system to the Davis VHF Radar at the University of Adelaide's Buckland Park field station has delivered excellent results. This antenna is capable of operation with the full power of the Davis ST VHF radar. The sister transmitter at BP has been optimised and a procedure developed to apply this on the Davis system. The new combiner unit has been operated routinely at Buckland Park and a catastrophic failure mode identified and rectified.

The Davis 55 MHz atmospheric radar can be run in a meteor detection mode by selecting an alternate set of transmitting and receiving antennas. These consist of a single circularly polarized transmitting antenna and five linear polarized receiving antennas arranged in a 'Mills Cross' configuration. Approximately 10 percent of radar observing time is committed to these observations although that figure has been larger at times through the life of the project.
In meteor mode, circularly polarized pulses are transmitted at a high repetition rate and the received signal is sampled at ranges sensitive to returns from the altitude range of 80-110 km approximately. If a meteor trail is present in the antenna field of view, increases of power of duration less than are second can be detected. The range is calculated from the pulse transit time and the direction of arrival is inferred from the relative phases of the signals at each receive antenna. Data files with a '.met' extension contain the analysed data products from these detections and these include:
Event start time - The time of the detection
Range - The distance from the radar to the meteor trail
SNR - The signal to noise ratio of the detection
Angle of arrival - The azimuth and zenith angles of the direction from the radar to the meteor trail
Decay time - The exponential decay time of the detected signal (and its error)
Diffusion coefficient - An inferred trail diffusion coefficient (and its error)
Radial velocity - The speed with which the trail was moving toward or away (positive) from the radar (and its error)
Phase differences - The mean phase differences for each pair combination of the five antennas.
(See attached description of the 'met' analysed data record for more information.)

If enough meteors are detected, it is possible to infer a horizontal wind field at the height of the detections. This is done my assuming the wind flows without divergence or convergence in the vicinity of the radar over a selected averaging interval. Horizontal and vertical components of the wind are derived in this way and stored with their heights. These data are stored in files with a '.vel' extension. (See attached description of 'vel' postanalysed data records for more information.)