WARNING: Version-1 MST radar data products are DEPRECATED
Users are encouraged to make use of Version-2 Cartesian files.
Click here to find out more about
the different versions of the signal processing.
The files contain altitude profiles (from approximately 2 - 20 km for
the ST mode, and from approximately 58 - 96 km for the M mode, both at
150 m intervals) of the eastward, northward and upward components of
the wind velocity and the following radar return parameters: vertical
beam signal power, aspect sensitivity, spectral width and
beam-broadening corrected spectral width. 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.
Click here to find out about the
contents of other files.
File naming convention:
contains 300 m resolution Cartesian data over the ST altitude
range for 1st June 2003.
||is a 4-digit year [1990 - ]
||is a 2-digit month [01 - 12]
||is a 2-digit day [01 - 31]
||is the altitude mode ['st': approximately 2 - 20 km | 'm': approximately 58 - 96 km]
||is the range resolution (m) [150 | 300 | 600 |
1200 | 2400 | 4800]
Click here for the background to the
file naming convention.
File location: /badc/mst/data/mst-products-v1/cartesian/
Click here for the location of other files.
Archiving convention: YYYY/MM
Click here for a further explanation.
Version-1 products are primarily available for the period 1st June
2003 - 31st Decemeber 2004.
NASA-Ames files, with a File Format Index of 2110, are used. i.e. the
same as for Version-2 data
products. However, there are some small differences in the file
Only those aspects of the file format which are essential for reading
the data will be described. For a full description of the NASA-Ames
formats, consult the Gaines
and Hipskind  document.
The Cartesian file for 1st June 2003 will be used as an example. Text
in green represents actual file contents. Text in red is for
explanatory purposes only.
Data reading loop
- Line 1: 93 2110
Integer 1 corresponds to the total number of header lines,
Integer 2 corresponds to the File Format Index
- Line 7: 2003 06 01 2003 06 12
Integers 1 - 3 correspond to the year, month and day on which the observations were made.
Integers 4 - 6 correspond to the year, month and day on which the file was created.
- Line 13: 9999.99 9999.99 9 99 999.999 9 999.99 9 999.99 9 99.999 9 99.999 9
These are the numbers which represent missing data values for the
'primary variables' (see below)
- Line 40: 130 515
Integer 1 corresponds to the number of altitude gates per cycle,
Integer 2 corresponds to the number of cycles in the file,
After reading the above mentioned lines, wind forward to line (nr_header_lines + 1) where the data
begin. Associated with each cycle of observation there is a single
line of auxiliary variables followed by nr_gates lines of primary variables. The data
can therefore be read with a simple loop structure of the form (shown
here in Fortran syntax):
do cycle_nr = 1,nr_cycles
do gate_nr = 1,nr_gates
Reading auxiliary variables
The auxiliary variables line contains 5 integers, shown here for the
first cycle in the file:
105 130 1 10936 3
Reading primary variables
- Integer 1: Cycle time (s)
Technically speaking this is the second independent variable
rather than an auxiliary variable. The time is given in seconds
since 00:00:00 UTC for the day in question.
- Integer 2: Number of range gates
This is the same as nr_gates given in
line 40 of the header and so can be ignored.
- Integer 3: Cycle number
This is the same as cycle_nr used in the
data reading loop and so can be ignored.
- Integer 4: Tropopause altitude (m)
This is the altitude of the (static stability) tropopause, in
metres above mean sea level, determined from the altitude profile
of the vertical beam signal strength.
- Integer 5: Tropopause sharpness factor
0 corresponds to an indefinite tropopause
1 corresponds to lower-intermediate sharpness
2 corresponds to upper-intermediate sharpness
3 corresponds to a definite tropopause
Note that when the tropopause is indefinite, i.e. when the sharpness
factor is 0 or 1, the tropopause altitude might have little meaning.
Each primary variable line contains 15 values (a mixture of floating
point numbers, F, and integers, I), shown here for the first line of the first
1686.0 1.81 7.98 3 0 0.015 3 66.26 3 11.56 3 0.204 3 0.158 3
Data Reliability flags
- Value 1: Altitude (m) F
Technically speaking this is the first independent variable rather
than a primary variable. The same altitude grid is used for all cycles
and so only needs to be saved once. The altitude is given in metres
above mean sea level.
- Value 2: Eastward wind (m s-1) F
or zonal velocity
- Value 3: Northward wind (m s-1) F
or meridional velocity
- Value 4: Horizontal wind reliability flag
This applies to both the eastward and northward components of the
wind. The same convention is used for the reliability flags
associated with all parameters - see below
- Value 5: Complementary beam horizontal velocity variability factor (m s-1) I
This is an experimental horizontal wind reliability factor and can
be ignored. In the standard-mode, the MST radar makes observations
in the Vertical, NE6, SE6, SW6 and NW6 beam directions. The NE
component of the horizontal wind can therefore be derived from the
Vertical/NE6 or Vertical/SW6 beam pair combinations. Similarly the
SE component can be derived from the Vertical/SE6 or Vertical/NW6
combinations. The variability factor is defined as the root of the
sum of the squares of the differences between the estimates in the
NE and SE azimuths. A small value - less than 5 m/s - indicates
that that the different wind estimates are consistent. Larger
values indicate that they are not and suggest that the associted
velocity components are probably unreliable.
- Value 6: Upward air velocity (m s-1)
Note that this value can be biased for a number of reasons and
should be interpreted as being representative rather than
necessarily as quantitatively accurate. In particular, little
significance should be attached to values of less than
approximately 0.1 m/s. Absolute values of the order of 1 m/s give
a reliable indication of the presence of mountain wave or convective
- Value 7: Upward air velocity reliability flag
- Value 8: Radar return signal power (dB)
Corresponds to obervations made with a vertically directed beam.
P(dB) = 10 × log10[P(linear)]
- Value 9: Radar return signal power reliability flag
- Value 10: Radar return aspect sensitivity (dB)
The ratio of radar return signal power for a vertically directed beam to that for a beam directed 6° off-vertical.
- Value 11: Radar return aspect sensitivity reliability flag
- Value 12: Radar return spectral width (m s-1)
This is for observations made by a vertically directed beam and
corresponds to to an e-1/2 half-width for a Gaussian shaped
signal. Note these values need to corrected for the effects of
beam-broadening before they can be interpreted in terms of
- Value 13: Radar return spectral width reliability flag
- Value 14: Beam-broadening corrected spectral width (m s-1) F
This is the highest order radar data product and is sensitive to
errors and uncertainties in several lower order products. Care
should therefore be taken with its interpretation. In principal it
gives the standard deviation of turbulent velocities about the
mean vertical velocity.
- Value 15: Beam-broadening corrected spectral width reliability flag
The same convention is used for all reliability flags:
For most purposes, the temporal continuity is much more significant
than the signal strength in terms of reliability. It is therefore best
to reject all data points with flag values of 0 or 1 and accept those
with values of 2 or 3. However, the temporal continuity algorithm is
not perfect. Under conditions of a sharp (temporal) increase in wind
speed, or the presence of large amplitude mountain wave activity, high
signal strength data points can be flagged as having poor temporal
continuity, i.e. with a reliability flag value of 1, even when they
are apparently reliable. If you are having difficulties with a
particular dataset, please contact the NERC MST Radar Facility Project
- 0: poor signal strength, poor temporal continuity
- 1: good signal strength, poor temporal continuity
- 2: poor signal strength, good temporal continuity
- 3: good signal strength, good temporal continuity
The values of the radar return aspect sensitivity, radar return
spectral width and beam-broadening corrected spectral width are a
little more sensitive to the signal strength. Care should therefore be
taken with the interpretation of values which have a reliability flag
value of 2.
- Return to the top of the page
- Gaining access to the data
- File naming convention
- Data archiving convention
- Data locations
- The differences between
signal processing versions
- The contents of other data files
description of the NASA-Ames formats: Gaines and Hipskind