THE NERC MST RADAR FACILITY AT ABERYSTWYTH
Click here to find out more about the different versions of the signal processing.
File contents
These files contain 12 minute averaged radial (i.e. along-beam) profiles of the radar return parameters (signal-to-noise ratio, signal power, Doppler shift and signal width) for different beam pointing directions. The same data are stored in ASCII format files - please contact the NERC MST Radar Facility Project Scientist for more details.
Click here to find out about the contents of other files.
File naming convention:
 |
YY | |
is a 2-digit year [00 - 99] |
| MM | is a 2-digit month [01 - 12] | ||
| DD | is a 2-digit day [01 - 31] |
File location: /badc/mst/data/mst-products-v0/radial/
Click here for the location of other files.
Archiving convention: YYYY
Click here for a further explanation.
File availability
1990 to the present.
File format
The data are recorded in non-standard format binary files as descibed below:
RADIAL WIND FILES
-----------------
File name :- RDFyyMMdd.DAT where yyMMdd is the date.
RANDOM ACCESS FILE - FORMATTED
RECORD - 36 BYTES
Data is FORMATTED unless stated otherwise.
For UNFORMATTED data:
B = BYTE
I2 = INTEGER*2 (2 byte integer)
I4 = INTEGER*4 (4 byte integer)
DATA IN RADIAL WIND (RDF) FILE
------------------------------
Each RDF file contains the results of processing the Doppler
spectra from the MST Radar for one day.
The results for each Doppler spectrum include:
the centre frequency of the peak,
the signal level,
the signal to noise ratio and
the estimated peak width.
The RDF file is formed by concatenating all Radial wind (RW) files
obtained on one day. These RW files have filenames RWyyMMdd_hhmm.nn
where hhmm is the time (UT) of the start of that data subset
and nn is the duration in minutes.
Each set of radial winds is calculated from the doppler spectra
from one beam direction (dwell) averaged over 12 minutes of
viewing in that direction.
The RDF file contains one header of peak extraction parameters
then alternating dwell header records and data records.
Peak Extraction Parameter records provide information about
the operating and processing parameters that were used.
Some records have an I1 identification field at the start to show
the type of information they contain.
The timing of the data can be read from the dwell header.
RECORD ORDERING.
----------------
The Peak Extraction Parameter Records only occur once per day,
at the start of the RDF file after the first RW file name.
The Dwell Header Records precede the Data Records to which
they apply.
Ident Record Comment
None Name of RW data file. Name of Radial wind file
that the data came from.
FIXED PARAMETERS HEADER:
4 Peak extraction parameters. Before first RW file only.
DWELL HEADER
None Dwell header for the first dwell
DATA:
None Peak frequency & (s,s/n,dF) first bin
None Peak frequency & (s,s/n,dF) second bin
etc. for six bins first data record
repeated for all height bins
DWELL HEADER
DATA for the next dwell
DWELL HEADER
DATA
etc. to the end of the RW file
None Name of RW data file. Name of next Radial Wind file
DWELL HEADER
DATA the first dwell of this file
etc.
0 Trailer.
RECORD FORMATS
--------------
Radial wind file name record.
-----------------------------
Name of RW file data came from. A20
Peak extraction parameter record.
---------------------------------
ONLY WRITTEN ONCE AFTER FIRST RW FILE NAME.
Contains parameters relating to the methods used to find the
spectral peak and estimate the doppler shift.
Identifier for Peak extraction record ( 4 ). I1
Algorithm number. I2
Peak width factor. F4
DC spike removal parameters. 4*I2
Dwell header
------------
Information relating to a dwell.
The following data is UNFORMATTED.
Dwell number in cycle. I2
Antenna beam number. I2
Radar pulse length, microsecs I2
Complementary code number. I2
Pulse repetition interval, microsecs ( IPI ). I2
Total integration count ( NPP ). I2
Length of FFT ( LFT ). I2
Number of FFTs that have been averaged. I2
Receiver filter (microsecs) (1/bandwidth) I2
MST run number. I2
Mean time, yy MM dd hh mm ss . 6*B
First height bin range (NH1,NH2). 2*I2
Second height bin range (NH3,NH4). 2*I2
Height bin increment. I2
Data record.
------------
Information derived from Doppler spectra.
Get heights from the bin parameters in the dwell header:
Data bins are NH1 to NH2 followed by
NH3 to NH4 if upper height data was collected.
The following data is UNFORMATTED.
Doppler frequency of peak ( milli Hertz ) I2
The 3 values below given as a 4 byte integer I4
Signal to noise, ( 0.1 dBs ) + 1024 11 Least Significant Bits
Signal strength, ( 0.1 dBs ) + 1024 Next 11 bits
Width of peak ( FFT points ) 10 Most Significant Bits
Width of peak can be expressed in Hz
by multiplying the value in FFT points by
1.0 / ( 1E-6 * IPI * NPP * LFT )
Thus data for one height bin uses I2+I4=6 bytes
Each data record includes data for 6 bins ( 36 bytes )
The last record of a dwell usually has less.
Trailer record.
---------------
Indicates end of data in the file.
Identifier for Trailer record ( 0 ). I1
HEIGHT DERIVATION
-----------------
Height at range bin n is given by :- Ht = (n - Bz) * HI
Bz is the sea level range bin,
derived as follows from dwell header parameters:
NRX = Receiver filter (microsecs).
LTX = Transmitter pulse width (microsecs).
If NRX = 1 Bz = 5.7 ( unless LTX = 1 when Bz = 5.2 )
If NRX = 2 Bz = 6.7
If NRX = 4 Bz = 8.7
If NRX = 8 Bz = 12.7
HI is the height increment per bin.
derived as follows from dwell header parameter:
NBM = Antenna beam number.
If NBM = 0 HI = 0.15 Km. ( Vertical )
If NBM = 1,3,5 or 7 HI = 0.1496 Km. ( 4.2 Deg. )
If NBM = 2,4,6 or 8 HI = 0.1484 Km. ( 8.5 Deg. )
If NBM = 9,11,13 or 15 HI = 0.1492 Km. ( 6.0 Deg. )
If NBM = 10,12,14 or 16 HI = 0.1467 Km. ( 12.0 Deg.)
This description was last updated 16 February 1995.