THE NERC MST RADAR FACILITY AT ABERYSTWYTH

File format for MST Radar Cardinal data files, version 4.0

The version 4 MST Radar data processing scheme is the latest version. The v4.0 Cardinal data files described on this page should be used in preference to any data files produced by earlier processing schemes.

File contents
The files contain altitude profiles (from approximately 2 - 20 km) of the eastward, northward and upward components of the wind velocity and of the following MST Radar data products: (vertical beam) signal power, (vertical beam) spectral width, (beam-broadening) corrected spectral width, and aspect sensitivity. The time separation between the profiles is typically a few minutes. A radar-derived tropopause altitude and sharpness is given for each set of profiles.
Availability Data processed by version 4.0 software are being tested and can be created on request - contact the NERC MST Radar Facility Project Scientist.

File naming convention:
nerc-mstrf-radar-mst_capel-dewi_YYYYMMDD_stRRR_cardinal_SSmin-smoothing_v4-0.nc

YYYY is a 4-digit year
MM is a 2-digit month [01 - 12]
DD is a 2-digit day [01 - 31]
RRR is the range resolution (m) [150 | 300 | 600 | 1200 | 2400 | 4800]
SS is the number of minutes smoothing in time
.nc represents that this is a netCDF file

i.e. nerc-mstrf-radar-mst_capel-dewi_20170327_st300_cardinal_33min-smoothing_v4-0.nc contains Cardinal data for 27th March 2017, st altitude coverage at 300 m range resolution.
Click here for the background to the file naming convention.

File location:
/badc/mst/data/nerc-mstrf-radar-mst/v4-0/st-mode/cardinal/

Archiving convention: YYYY/MM
Click here for a further explanation of archiving conventions .

netCDF File Structure using the st300 file for 27th March 2017 as an example - click here for an explanation of netCDF file structure.
List of Global attributes - Click on the name to view the value
char Conventions
char title
char source
char institution
char history
char references
char comment
char license
char featureType
byte data_product_level
char creator_name
char creator_email
char platform_name
char platform_type
char platform_record_url
char instrument_record_url
byte instrument_altitude_above_mean_sea_level_m
float instrument_radio_frequency_Hz
float instrument_beam_one_way_half_power_half_width_degrees
float instrument_antenna_side_length_m
short observation_year
byte observation_month
byte observation_day
char observation_altitude_mode
short observation_range_resolution_m
short observation_range_resolution_number
short observation_bottom_range_gate_number
short observation_top_range_gate_number
byte processing_version_number
byte processing_sub_version_number
short processing_cardinal_nominal_smoothing_period_minutes
char comment_processing_changes
char comment_instrument_location
char comment_instrument_technique
char comment_horizontal_wind
char comment_tropopause
char comment_vertical_beam
char comment_dB_units
char comment_qc_flag
char comment_qc_details
List of Dimensions - Click on the name to view the corresponding coordinate variable
altitude
time
List of Variables - Click on a name to view the corresponding attributes
float latitude()
float longitude()
float time(time)
float altitude(altitude)
float eastward_wind(time, altitude)
float northward_wind(time, altitude)
float upward_wind(time, altitude)
float signal_power(time, altitude)
float aspect_sensitivity(time, altitude)
float corrected_spectral_width(time, altitude)
float tropopause_altitude(time)
byte tropopause_sharpness(time)
float noise_power(time)
byte qc_flag_horizontal_wind(time, altitude)
byte qc_flag_vertical_beam(time, altitude)
short qc_details_vertical_beam(time, altitude)
byte qc_flag_aspect_sensitivity(time, altitude)
byte qc_flag_corrected_spectral_width(time, altitude)
float horizontal_wind_compensation_factor(time, altitude)
byte number_of_cycles_in_smoothing_period(time)
float spectral_width(time, altitude)
List of Global Attribute values
char Conventions = "CF-1.6"

char title = "
  Altitude profiles of wind components along the cardinal directions and
  of other parameters derived from observations made by the NERC MST
  Radar at Capel Dewi (near Aberystwyth), UK in st300 mode on
  2017-03-27.
"

char source = "
  The Natural Environment Research Council (NERC)
  Mesosphere-Stratosphere-Troposphere (MST) Radar at Aberystwyth
"

char institution = "
  The Natural Environment Research Council (NERC)
  Mesosphere-Stratosphere-Troposphere (MST) Radar Facility at Aberystwyth,
  http://mst.nerc.ac.uk, is funded by NERC through the National Centre for
  Atmospheric Science (NCAS), https://www.ncas.ac.uk/. It is managed by
  RAL Space at the Science and Technology Facilities Council's (STFC)
  Rutherford Appleton Laboratory (RAL), https://www.ralspace.stfc.ac.uk/.
  The data held by the Centre for Environmental Data Analysis (CEDA),
  http://catalogue.ceda.ac.uk/uuid/bd095d86e4a9f0c706b08058dbad3b31.
"

char history = "
  2017-05-04T13:54:57 - netcdf file created on computer jasmin-sci2.ceda.ac.uk.
  2017-05-04T14:01:22 - data passed visual quality control check and file delivered to CEDA for ingestion into archives.
"

char references = "
  The following publications mostly relate to wind data quality and
  representativeness. They are referred to in other global/variable
  attributes.
   Thomas, L., I. Astin, and R. M. Worthington (1997). A statistical
  study of underestimates of wind speeds by VHF radar. Ann. Geophys.,
  15, 805-812. DOI: 10.1007/s00585-997-0805-8.
   Hooper, D. A., and J. Arvelius (2000). Monitoring of the Arctic winter
  tropopause: A comparison of radiosonde, ozonesonde and MST radar
  observations. Proceedings of the Ninth International Workshop on
  Technical and Scientific Aspects of MST Radar, pages 385-388. Sci. Comm.
  on Sol.-Terr. Phys. Secr., Boulder, Colorado, USA.
   Hooper, D. A., J. Nash, T. Oakley, and M. Turp (2008). Validation of a
  new signal processing scheme for the MST radar at Aberystwyth. Ann.
  Geophys., 26(11), 3253-3268. DOI: 10.5194/angeo-26-3253-2008 .
   Parton, Graham, Anthony Dore, and Geraint Vaughan (2010). A
  climatology of mid-tropospheric mesoscale strong wind events as observed
  by the MST radar, Aberystwyth. Meteorol. Apps., 17, 340-354, 2010.
  DOI: 10.1002/met.203 .
   Hooper, David A., David M. Edwards, Gemma Holmes, Kevin Linklater,
  Tim Oakley, Colin Parrett, and Myles Turp (2013). The usefulness of
  model-comparison statistics for wind-profiling radar operators. In
  R. Latteck and W. Singer, editors, Proceedings of the Thirteenth
  International Workshop on Technical and Scientific Aspects of MST
  Radar, pages 141-150. Leibniz-Institute of Atmospheric Physics at the
  Rostock University, Kuhlungsborn, Germany. Available from
  http://purl.org/net/epubs/work/11539671 .
   Lee, C. F., G. Vaughan, and D. A. Hooper (2014). Evaluation of wind
  profiles from the NERC MST radar, Aberystwyth, UK. Atmos. Meas. Tech.,
  7(9), 3113-3126. DOI: 10.5194/amt-7-3113-2014 .
"

char comment = "
  Refer to global attributes whose names begin with 'comment_' for more
  information about the data.
"

char license = "
  Use of the data is covered by the (UK) Open Government Licence,
  http://www.nationalarchives.gov.uk/doc/open-government-licence/
"

char featureType = "timeSeriesProfile"

byte data_product_level = 3

char creator_name = "David A. Hooper"

char creator_email = "david.hooper@ncas.ac.uk"

char platform_name = "
  The Natural Environment Research Council (NERC)
  Mesosphere-Stratosphere-Troposphere Radar Facility (MSTRF), Capel Dewi
  (near Aberystwyth), UK.
"

char platform_type = "stationary_platform"

char platform_record_url = "http://catalogue.ceda.ac.uk/uuid/8b723580e0e5426d888b273e42f76c1b"

char instrument_record_url = "http://catalogue.ceda.ac.uk/uuid/6fcd4e23841b4aa0af75b8bb783011ea"

byte instrument_altitude_above_mean_sea_level_m = 50

float instrument_radio_frequency_Hz = 46500000.0

float instrument_beam_one_way_half_power_half_width_degrees = 1.5

float instrument_antenna_side_length_m = 104.120003

short observation_year = 2017

byte observation_month = 3

byte observation_day = 27

char observation_altitude_mode = "st"

short observation_range_resolution_m = 300

short observation_range_resolution_number = 2

short observation_bottom_range_gate_number = 18

short observation_top_range_gate_number = 147

byte processing_version_number = 4

byte processing_sub_version_number = 0

short processing_cardinal_nominal_smoothing_period_minutes = 33

char comment_processing_changes = "
  The version 4 (v4) processing scheme is closely related to the
  version 3 (v3) scheme described by Hooper et al. (2008) - see global
  attribute 'references'. The main difference is that the horizontal
  wind components in the v4 Cardinal files represent time averages over
  a nominal period given by the global attribute
  'processing_cardinal_nominal_smoothing_period_minutes'. This reduces the
  random measurement error of the single cycle estimates in the v3
  Cartesian files. A second difference is in the calculation of the factor
  used to compensate horizontal wind speeds for the effects of aspect
  sensitivity - see Thomas et al. (1997), Hooper et al. (2008), and
  Lee et al. (2014) in the global attribute 'references'. It was previously
  based on the (single cycle) ratio of signal powers observed at zenith
  angles of 4.2° and 6.0°. The v4 factor is based on the more-robust ratio
  of signal powers observed at zenith angles of 0.0° and 6.0°. Moreover,
  the signal powers are averaged over a nominal period given by the global
  attribute 'processing_cardinal_nominal_smoothing_period_minutes'. These
  improved estimates of horizontal wind are used to calculate values of the
  variable 'corrected_spectral_width'.
"

char comment_instrument_location = "
  The values of the variables 'latitude' and 'longitude' have been
  taken from a Global Positioning System (GPS) receiver that was placed
  close to the centre of the MST radar's antenna array. The coordinates
  should be accurate to within +/- 5 m. The value of global attribute
  'instrument_altitude_above_mean_sea_level_m' has been taken from
  the Ordnance Survey Landranger 135 map for the area. It should be
  accurate to within +/- 5 m.
"

char comment_instrument_technique = "
  The NERC MST Radar is a 46.5 MHz pulsed Doppler radar that is used to
  study the atmosphere. The radar returns are primarily from 'clear-air'
  targets, i.e. structures in atmospheric refractive index that have scale
  sizes of half the radar's wavelength (approximately 3 m) along the beam
  pointing direction. The refractive index depends on humidity (within the
  lowest 10 km of the atmosphere), on air density (within the lowest few
  10s of km), and on free electron density (above 50 km). The radar return
  signals are parameterised by their power, Doppler shift, and spectral
  width. The signal power depends on the vertical gradient of (potential)
  refractive index and so relates to atmospheric structure. The Doppler
  shift depends on the radial component of the wind along the beam
  pointing direction. Observations must be made in the vertical direction
  and at an off-vertical angle in at least two orthogonal azimuths in
  order for the three dimensional wind vector to be derived. The spectral
  width depends on the intensity of any turbulence with the radar
  observation volume. However, the values must be corrected for the
  effects of beam-broadening, which depends on the horizontal wind speed
  and on the radar's beam width.
"

char comment_horizontal_wind = "
  The horizontal wind components, given by variables 'eastward_wind' (v_E)
  and 'northward_wind' (v_N), have already been smoothed in time by a
  nominal amount given by the global attribute
  'processing_cardinal_nominal_smoothing_period_minutes'. If additional
  smoothing is required, either in time or in altitude, this should be
  applied to these components. Horizontal wind speeds (v_H) and directions
  can then be derived using the following relationships:
   v_H = sqrt(v_E^2 + v_N^2)
   phi_met = 180/pi * atan2(-v_E,-v_N)
   phi_vect = 180/pi * atan2(v_E,v_N)
  where sqrt indicates the square root, ^2 indicates squared, phi_met is
  the meteorological convention wind direction (i.e. from which it is
  blowing), phi_vect is the vector convention wind direction (i.e. towards
  which it is blowing), 180/pi is the conversion factor between angles in
  radians and in degrees, and atan2(y,x) is the four quadrant arctangent
  function. Note that some computing environments, such as Microsoft Excel,
  use an atan2(x,y) function for which the order of the arguments must be
  reversed.
"

char comment_tropopause = "
  The altitude and sharpness of the tropopause are derived from altitude
  profiles of the vertical beam signal power following Hooper and Arvelius
  (2000) - see global attribute 'references'. A tropopause sharpness value
  of 0 corresponds to a signal power gradient of less than 2.0 dB/km, a
  value of 1 to less than 3.5 dB/km, a value of 2 to less than 5.0 dB/km,
  and a 3 to greater than 5.0 dB/km. Note that these gradients are twice
  those used by Hooper and Arvelius (2000), which was based on signal
  amplitudes rather than powers. The tropopause details contained in the
  v3 Cartesian files are based on single cycle profiles of signal power.
  The values in the v4.0 Cardinal files are the medians of the v3 values
  taken over a nominal period given by global attribute
  'processing_cardinal_nominal_smoothing_period_minutes'.
"

char comment_vertical_beam = "
  The values of variables 'signal_power', 'upward_wind', and
  'spectral_width' are taken from the first vertical beam dwell of each
  observation cycle. They are taken from the range gates that are closest
  in altitude to those at 6.0° off-vertical, which are used to derive
  horizontal wind components. All three variables share the same quality
  control flag variable, 'qc_flag_vertical_beam', and quality details
  variable, 'qc_details_vertical_beam'.
"

char comment_dB_units = "
  Radar return signal powers have dimensions of watts. The values are
  uncalibrated and are stored in dB units, where
  P_dB = 10.0 * log10(P_linear-units). The ratio of signal powers in
  linear units is equivalent to the difference in dB units.
"

char comment_qc_flag = "
  For many of the variables in the v4 Cardinal files, an indication of
  which values are considered to be reliable is given by an associated
  quality control flag variable. The name of the latter is given by
  the 'ancillary_variables' attribute of the main variable (and the
  'associated_variables' attribute of a quality control flag variable
  gives the names of the main variables associated with it). A quality
  control flag value of 1 implies that the associated values are
  reliable. A value of 0 is never used and any value higher than 1 implies
  that the associated values are either unreliable or should only
  be used with caution. Refer to the 'flag_values' and 'flag_meanings'
  attributes of each quality control flag variable for specific details.
  In some cases, additional quality control details are given by an
  associated quality control details flag - see global attribute
  'comment_qc_details'.
"

char comment_qc_details = "
  In most circumstances it is best to make use of the associated quality
  control flag variable in order to determine which variable values are
  are considered to be reliable. The 'qc_details_vertical_beam'
  variable contains all of the information, encoded bitwise, used to
  determine the overall reliability. The same technique is used in the
  radial and Cartesian data files and so not all of the following bits
  are used for the vertical beam signal here.
   bit 00: 1 if the signal is available
   bit 01: 1 if the peak smoothed power spectral density (PSD) is greater
   than a set threshold above the noise Power Spectral Density.
   bit 02: 1 if the signal belongs to a radial chain
   bit 03: 1 if the signal fits overall radial continuity
   bit 04: 1 if a secondary signal belongs to a radial chain
   bit 05: 1 if the signal has passed a uni-directional time continuity
   test
   bit 06: 1 if the signal has passed a bi-directional time continuity
   test
"


List of Variable attribute values
float latitude()
standard_name = "latitude"
long_name = "Instrument latitude"
units = "degrees_north"
comment = "
  Refer to global attribute 'comment_instrument_location' for more
  details about this variable.
"
float longitude()
standard_name = "longitude"
long_name = "Instrument longitude"
units = "degrees_east"
comment = "
  Refer to global attribute 'comment_instrument_location' for more
  details about this variable.
"
float time(time)
standard_name = "time"
long_name = "Start time of observation cycle"
units = "seconds since 2017-03-27 00:00:00 +00:00"
axis = "T"
comment = "
  The values refer to the start of observation cycles. The data
  acquisition computer synchronises its clock using Network Time
  Protocol (NTP).
"
float altitude(altitude)
standard_name = "altitude"
long_name = "Altitude of observation above mean sea level"
units = "m"
axis = "Z"
comment = "The values refer to the centres of the range gates."
float eastward_wind(time, altitude)
standard_name = "eastward_wind"
long_name = "Eastward wind component"
units = "m s-1"
ancillary_variables = "qc_flag_horizontal_wind"
comment = "
  Refer to global attribute 'comment_horizontal_wind' for more details
  about this variable.
"
float northward_wind(time, altitude)
standard_name = "northward_wind"
long_name = "Northward wind component"
units = "m s-1"
ancillary_variables = "qc_flag_horizontal_wind"
comment = "
  Refer to global attribute 'comment_horizontal_wind' for more details
  about this variable.
"
float upward_wind(time, altitude)
standard_name = "upward_wind"
long_name = "Upward wind component"
units = "m s-1"
ancillary_variables = "qc_flag_vertical_beam"
v3_cartesian_file_variable_name = "vertical_beam_radial_velocity"
comment = "
  Refer to global attribute 'comment_vertical_beam' for more
  details about this variable. The values have an accuracy of the
  order of 0.1 m s-1, which means that they cannot be used to identify
  synoptic scale vertical velocities. However, they are well-suited
  for identifying mountain/convectively-generated waves and convection.
"
float signal_power(time, altitude)
long_name = "Vertical beam signal power"
units = "dB"
ancillary_variables = "qc_flag_vertical_beam"
v3_cartesian_file_variable_name = "vertical_beam_signal_power"
comment = "
  Refer to global attribute 'comment_vertical_beam' for general
  details about this variable. The tropopause altitude and sharpness
  values are derived from this parameter.
"
float aspect_sensitivity(time, altitude)
long_name = "Ratio of vertical to 6.0° off-vertical signal powers"
units = "dB"
ancillary_variables = "qc_flag_aspect_sensitivity"
comment = "
  Refer to global attribute 'comment_dB units' for general details about
  dB units. Each value is given by the ratio of the average signal
  powers for all vertical beam dwells and all 6.0° off-vertical dwells
  within an observation cycle.
"
float corrected_spectral_width(time, altitude)
long_name = "Beam broadening corrected vertical beam signal spectral width"
units = "m s-1"
ancillary_variables = "qc_flag_corrected_spectral_width"
v3_cartesian_file_variable_name = "beam_broadening_corrected_spectral_width"
comment = "
  Refer to global attribute 'comment_vertical_beam' for general
  details about this variable.
"
float tropopause_altitude(time)
standard_name = "tropopause_altitude"
long_name = "Radar-derived tropopause altitude"
units = "m"
comment = "
  Refer to global attribute 'comment_tropopause' for general details about
  this variable.
"
byte tropopause_sharpness(time)
long_name = "Radar-derived tropopause sharpness index"
units = "1"
flag_values = [0, 1, 2, 3]
flag_meanings = "indefinite lower_intermediate upper_intermediate definite"
v3_cartesian_file_variable_name = "tropopause_sharpness_factor"
comment = "
  Refer to global attribute 'comment_tropopause' for general details about
  this variable.
"
float noise_power(time)
long_name = "Vertical beam signal median noise power over altitude"
units = "dB"
v3_cartesian_file_variable_name = "vertical_beam_median_noise_power"
comment = "
  Refer to global attribute 'comment_dB_units' for general details about
  dB units.
"
byte qc_flag_horizontal_wind(time, altitude)
long_name = "Quality control/reliability flag for horizontal wind variables"
units = "1"
flag_values = [1, 2]
flag_meanings = "reliable not_reliable"
associated_variables = "eastward_wind northward_wind"
comment = "
  Refer to global attribute 'comment_qc_flag' for general details about
  quality control flag variables.
"
byte qc_flag_vertical_beam(time, altitude)
long_name = "Quality control/reliability flag for vertical beam signal variables"
units = "1"
flag_values = [1, 2]
flag_meanings = "reliable not_reliable"
associated_variables = "signal_power upward_wind spectral_width"
comment = "
  Refer to global attribute 'comment_qc_flag' for general details about
  quality control flag variables.
"
short qc_details_vertical_beam(time, altitude)
long_name = "Quality control/reliability details for vertical beam signal variables"
units = "1"
comment = "
  Refer to global attribute 'comment_qc_details' for general details about
  quality control details variables.
"
byte qc_flag_aspect_sensitivity(time, altitude)
long_name = "Quality control/reliability flag for aspect sensitivity values"
units = "1"
flag_values = [1, 2]
flag_meanings = "reliable unreliable"
associated_variables = "aspect_sensitivity"
comment = "
  Refer to global attribute 'comment_qc_flag' for general details about
  quality control flag variables.
"
byte qc_flag_corrected_spectral_width(time, altitude)
long_name = "Quality control/reliability flag for corrected spectral width values"
units = "1"
flag_values = [1, 2, 3]
flag_meanings = "reliable overcorrected unreliable"
associated_variables = "corrected_spectral_width"
comment = "
  Refer to global attribute 'comment_qc_flag' for general details about
  quality control flag variables. A flag value of 2 indicates that
  the beam broadening correction is larger than the observed spectral
  width and so the corrected value is set to zero. The associated
  corrected_spectral_width values are still worth plotting.
"
float horizontal_wind_compensation_factor(time, altitude)
long_name = "Horizontal wind aspect sensitivity compensation factor"
units = "1"
v3_cartesian_file_variable_name = "horizontal_wind_theta_s_compensation_factor"
comment = "
  The values of variable 'horizontal_wind_compensation_factor' are
  included for reference purposes only. They have already been applied
  to the values of variables 'eastward_wind' and 'northward_wind'. Refer
  to global attribute 'comment_processing_changes' for more details.
"
byte number_of_cycles_in_smoothing_period(time)
long_name = "
  The number of cycles available in the smoothing period used to derive
  the horizontal wind components.
"
units = "1"
comment = "
  Refer to global attribute 'comment_horizontal_wind' for general details
  about this variable.
"
float spectral_width(time, altitude)
long_name = "Vertical beam signal spectral width."
units = "dB"
ancillary_variables = "qc_flag_vertical_beam"
v3_cartesian_file_variable_name = "vertical_beam_spectral_width"
comment = "
  Refer to global attribute 'comment_vertical_beam' for general
  details about this variable. This variable is included for reference
  purposes only. Use should instead be made of variable
  corrected_spectral_width for turbulence information.
"