WARNING: Version-2 MST radar data products are DEPRECATED
Users are encouraged to make use of version-3 Cartesian files.
Click here to find out about
earlier 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 January 2005.
||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-v2/cartesian/
Click here for the location of other files.
Archiving convention: YYYY/MM
Click here for a further explanation.
Data availability: refer to Instrument
NASA-Ames files, with a File Format Index of 2110, are used, i.e. the
same as for Version-1 data
products. However, there are some small differences in the file
contents. Users will therefore need to make a few modifications to any
software designed for dealing with Version-1 products.
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 January 2005 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: 95 2110
Integer 1 corresponds to the total number of header lines,
Integer 2 corresponds to the File Format Index
- Line 7: 2005 01 01 2005 01 10
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 11: 14
The number of primary variables (nr_primary_vars).
- Line 13: 9999.99 9999.99 99999 99 999.999 99999 999.99 99999 999.99 99999 99.999 99999 99.999 99999
Missing data values, in order, for the nr_primary_vars primary variables listed below. Greater use is made
of missing data values than in the Version-1 files and so users should make
sure that they make the appropriate substitutions when they read
in the data.
- Lines 14 - 27
The names of the primary variables (listed below)
- Line 40: 130 366
Integer 1 corresponds to the number of altitude gates per cycle,
Integer 2 corresponds to the number of cycles in the file,
- Lines 41 - 66:
Data product definitions - this
information is shown, further down the page, in association with the
relevant primary variables.
- Lines 67 - 93:
Global data attributes following the netCDF CF 1.0
convention. This includes a processing history. It is not
necessary to know this information in order to read 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
Each auxiliary variables line contains 5 integers (the second
independent variable followed by the 4 auxilliary variables) shown
here for the first cycle in the file:
116 130 1 11086 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
It should be noted that the altitude can have little significance for
a poorly defined tropoapuse, i.e. for low values of the sharpness
||corresponds to an indefinite tropopause
||corresponds to lower-intermediate sharpness
||corresponds to upper-intermediate sharpness
||corresponds to a definite tropopause
These lines contain 15 values: the first independent variable (altitude)
followed by the 14 primary variables, as shown below for the first
line of the first cycle. These are a mixture of floating
point, F, and integer, I values.
1686.0 16.13 -3.36 32799 7 0.116 32771 57.82 32771 4.19 32771 0.309 32771 0.169 32771
Data Reliability flags
- Value 1: Altitude (m) F
Technically speaking this is the first independent variable rather
than a primary variable. Therefore it does not have a missing data
value defined in line 13 of the
header. Missing data values 1 - 14 therefore correspond to values
2 - 15 on the primary variable data line. 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 way in which information is recorded in the reliability
flag values is different to that used in Version-1 files. However,
the same convention is used for all reliability flags in the
Version-2 files - see below
- Value 5: Complementary beam horizontal velocity variability factor (m s-1) I
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 - greater than 10 m/s - indicate that they are not and this
fact is recorded in an enhanced data
- 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 in the Version-2
files, although this differs from that used for Version-1 files. A larger range of
information is now stored bit-wise in a 16-bit integer, with the 15th
bit being used as an overall indicator of data reliability. Therefore
data may be regarded as reliable if:
flag value >=
The convention has been adopted so that more pieces of information can
be added to the flag value at a later date, without changing the
acceptance condition. At present, only 6 of the available 16 bits are
The threshold values used for a particular file are quoted in header
lines 56 - 61.
||peak signal PSD to noise PSD >= threshold value
||time continuity threshold exceded
||complementary beams are available
||complementary beam factor >= threshold value
||complementary beam factor is significant
||overall reliability flag
- 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