Davis 55MHz Mesosphere Stratosphere Troposphere radar winds and echo characteristics

Full description

This dataset contains wind speed, direction and associated information in the troposphere, lower stratosphere and mesosphere above Davis, Antarctica. The radar runs continuously. Data are collected and stored approximately every minute (excluding downtime for maintenance) over height ranges and resolutions that are determined by experiment parameters. Analysis of the source data yields parameters describing the radial velocity, and radar echo strength and character for defined radar beam pointing directions.

Radar beams are formed by phasing the entire 12x12 antenna array. Beam directions are chosen from vertical or off-vertical pointing to the north, south, east or west. Their zenith angle is typically 14 or 7 degrees depending on the upgrade status of the radar. The capability to form groups of 4x6 antennas existed prior to an upgrade in the beam steering system. Pulse shape and duration is configurable as is the pulse repetition frequency (within the design limits of the radar).

Sampled height ranges typically encompass the troposphere and lower stratosphere (e.g. 2-15 km) or the mesosphere (e.g. 70-90 km). The resolution and extent of the sampled range are limited by acquisition memory. Pulse repetition frequencies are sometimes chosen to ‘range-alias’ height ranges to lower sampled ranges. Coherent averaging of the echoes from successive pulses is possible.

Combinations of these options are chosen for particular observing modes. These are described in ‘experiment’ configurations. These typically have a duration of less than a minute and repeat on cycles of 6-8 minutes (configurable).

These configuration options yield a variety of data files.

Postanalysis of experiment data files can be configured on the radar. Wind-field fits and averages can be formed in this way. A data quality control algorithm was sometimes applied in this way to yield data files with ‘_clean’ in their name.

Data collection began in 2003 and is ongoing. Files are named using their start date (and time), an experiment tag and an extension describing their format. Technical issues with the radar have affected the quality of some data sets as will be described below.

MST stands for Mesosphere Stratosphere Troposphere, which refer to the atmospheric regions that the radar can sense (although not all year round). The radar is also sometimes referred to as a ‘VHF radar’ due to the 55MHz radar frequency which is in the VHF band.

Project History:
The operation of the MST radar has supported a number of Antarctic Science Research projects. These include:
Project 2325 – ‘VHF Radar Studies of the Antarctic Mesosphere, Stratosphere and Troposphere’. 2002/03 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
Project 674 – ‘Dynamical coupling in the Antarctic middle atmosphere’ 2002/03 to 2011/12.
Project 737 – ‘Lidar studies of atmospheric dynamics, composition and climatology’. 2002/3 to 2011/12.
Project 2529 – ‘A Meteor Radar for Measuring Mesospheric and Lower Thermospheric Winds and Temperatures at Davis Station’. 2004/05 to 2008/09.
Project 2668 – ‘Investigations of the Antarctic Mesosphere and Lower Thermosphere using satellite data’. 2005/06 to 2011/12.
Project 3140 – ‘Dynamical Variability of the Lower Atmosphere’. 2009/10 to 2011/12.

Further details of the outcomes of these projects can be found on the Antarctic Division website www.aad.gov.au.

Technical History:
Summer 2002/03 – Installation of 144 antenna phased array (in hybrid Doppler-spaced antenna configuration), single power amplifier transmitter system, transceiver and control system. Array tuning issue identified. Separate add-on meteor detection radar system was also installed at this time.
Summer 2003/04 – Attempt to upgrade transmitter system to full power was delayed by technical faults. Temporary installation of ATRAD supplied transmitter.
Summer 2004/05 – Replacement transmitter, transceiver and control system installed. Beam steering unit upgraded to decrease ‘clutter’ near zero Hz.
Summer 2008/09 – Contact grease inserted into connectors in attempt to alleviate clutter problems.
Summer 2010/11 – Bias in tropospheric wind results obtained using hybrid array and FCA analysis identified. Doppler observations shown to compare favourably to radiosondes.
Summer 2012/13 – Antenna array reconfigured to Doppler only. Beam Steering unit replaced with Power combiner-splitter/beam steering unit combination.
Winter 2013 – High voltage power supply failure. Radar operated through winter on low power solid state preamplifiers.
Summer 2013/14 – High voltage, 50V and heater current power supplies upgraded.
Summer 2014/15 – Beam steering unit relay switch timing error was identified and found to cause relay damage. Some sticking relays replaced after timing changed.
Summer 2016/17 – Beam steering unit relay replacement completed.

Lineage

Progress Code: onGoing

Statement: Data quality has varied through the life of the radar due to technical enhancements. Factors affecting each data type and their implications are described below. Full correlation analysis. (data file extension .fca) Full correlation analysis was possible while the antenna array was configured for hybrid Doppler-Spaced antenna operation. However, these data were found to be affected by coupling between antennas, which significantly degraded the quality of wind estimates. FCA analysis was applied to summer mesospheric observations and the resulting power and signal to noise ratios were not adversely affected. These files have names of the form YYYYMMDD_meso.fca Doppler Beam Steering. (data file extension .dbs) When the whole antenna array is configured to form a beam, the DBS analysis can be used to estimate the radial velocity in the direction of the beam (Vertical, N, S, E or W). Prior to the upgrade to Doppler only, the off-zenith angle used was approximately 7 degrees. After the upgrade it was hardware limited to 14 degrees. Tropospheric wind measurements obtained using off-vertical beams were found to have small but acceptable biases compared to radiosonde observations. DBS analysis could be applied to data collected using the FCA configuration to form a vertical beam. These data provided acceptable measures of power and signal to noise ratio. These files have names of the form YYYYMMDD_tropo.dbs and YYYYMMDD_meso.dbs. Dual beam Doppler observations are used to measure the momentum flux of atmospheric waves. These require N,S,E and W beams for their analysis. Such files have names of the form YYYYMMDD_tropoMF.dbs. Note that these files contain range aliased mesospheric observations. Velocity files. (data file extension .vel) Postanalysis that combines .dbs files for different pointing directions is used to create velocity files with a .vel extension. The duration of the data set used to create this is configurable. The _seq phrase is used to describe files that are collated from one six minute sequence.