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INTERNAL LINKS
THE NERC MST RADAR FACILITY AT ABERYSTWYTH
FILE FORMAT FOR VAISALA WXT510 PRECIP DATA
File contents
The files contain rainfall rate and accumulation (precip) data from the Vaisala WXT510 weather transmitter - a surface met data logging instrument. For details about other data products from this instrument, click on one of the following links:
ptu
wind
Click here to find out about the contents of other files.

Availability: Data are available from 21st December 2007 until the present.

File naming convention:
nerc-mstrf-met-sensors_capel-dewi_YYYYMMDD_wxt510-precip.nc

YYYY is a 4-digit year [1990 - ]
MM is a 2-digit month [01 - 12]
DD is a 2-digit day [01 - 31]
.nc represents that this is a netCDF file

Click here for the background to the file naming convention.

File location: /badc/mst/data/met-sensors-wxt510-precip
Click here for the location of other files.

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

netCDF File Structure using the file for 21st December 2007 as an example - click here for an explanation
List of Global attributes - Click on the name to view the value
short file_version_number
short data_year
short data_month
short data_day
char Conventions
char title
char institution
char source
char history
char references
char comment
List of Dimensions - Click on the name to view the corresponding coordinate variable
time
List of Variables - Click on a name to view the corresponding attributes
float longitude ()
float latitude ()
float altitude ()
float height ()
integer time (time)
float rainfall_rate (time)
float rainfall_accumulation (time)
float hail_rate (time)
float hail_accumulation (time)
List of Global Attribute values
short file_version_number = 1

short data_year = 2007

short data_month = 12

short data_day = 21

char Conventions = "CF-1.3"

char title = "
  Surface meteorological data (precip) from the NERC MST Radar Facility at
Aberystwyth
"

char institution = "
  Data recorded by the Natural Environment Research Council (NERC)
Mesosphere-Stratosphere-Troposphere (MST) Radar Facility at Aberystwyth -
http://mst.nerc.ac.uk
  Data processed by the Rutherford Appleton Laboratory, Space Science and
Technology Department - http://www.sstd.rl.ac.uk
  Data held at the British Atmospheric Data Centre -
http://badc.nerc.ac.uk/data/mst
"

char source = "Vaisala Weather Transmitter WXT510"

char history = "File created 2008-08-28 11:04:47 +00:00 on machine claudius"

char references = "
  Basic information about the data is available at
http://badc.nerc.ac.uk/data/mst
  More detailed information about the data is available at
http://mst.nerc.ac.uk
  The manufacturer's details about the instrument can be found at
http://www.vaisala.com
"

char comment = "
  The Vaisala Weather Transmitter WXT510 is a single unit which
measures a variety of surface meteorological parameters in three
independent measurement cycles. Pressure, temperature and relative
humidity (ptu) are measured in the first cycle, precipitation (precip)
in the second, and wind speed and direction (wind) in the third. The
data (for a given day) from each of these cycles are stored in
separate files with respective names of the format:
  nerc-mstrf-met-sensors_capel-dewi_YYYYMMDD_wxt510-ptu.nc
  nerc-mstrf-met-sensors_capel-dewi_YYYYMMDD_wxt510-precip.nc
  nerc-mstrf-wind-sensors_capel-dewi_YYYYMMDD_wxt510.nc
where YYYYMMDD is an 8-character string representing the date. Missing
data values are used to indicate gaps in data collection.
  Pressure is measured by a silicon BAROCAP (R) sensor, temperature by
a capacitive ceramic THERMOCAP (R) sensor, and relative humidity by a
capacitive thin film polymer HUMICAP (R) 180 sensor. These are
simultaneously sampled at 60 s intervals.
  Precipitation is measured by a RAINCAP (R) piezoelectric sensor,
which has an area of 60 cm2. The signal generated by the impact of a
single raindrop is proportional to its volume. Internal signal
processing is used to differentiate between the signals generated by
rain, hail and undesired sources. Nevertheless, occasional small rain
accumulations appear to be unrelated to precipitation. Data messages
are only generated for the duration of a precipitation event, when
they are available at 10 s intervals. The rainfall and hail
accumulations represent the amounts since the last non-zero
readings. The rates represents the mean values over the preceding 60
s. Within the first 60 s of a precipitation event, the rates are
evaluated only over the period since the start time of the event.
  Wind speed and direction are measured by a WINDCAP (R) sensor. This
consists of an array of three equally-spaced ultrasonic transducers
(approximately 11 cm apart) in a horizontal plane. The time it takes
for sound to travel between each pair of transducers depends on the
temperature and the humidity of the air and on the component of wind
vector along the direction joining the transducers. For a given pair
of transducers, the effects of temperature and humidity are the same
for the sound travelling in both the forward and the reverse
directions. However, the effects of the wind vector are
opposite. Measurements are required between at least two pairs of
non-collinear transducers in order to derive the wind speed and
direction. The use of measurements from all three pairs of transducers
provides redundancy, which allows the wind information to be derived
from the two pairs of transducers which provide the best quality
signals. No attempt is made to calculate the wind direction when the
speed drops below 0.05 m s-1. Instead, the last calculated direction
is used until the wind speed rises back above 0.05 m s-1. Samples of
wind speed and direction are taken 4 times a second over 3
seconds. From these 12 samples, the minimum, mean, and maximum values
of speed and direction are recorded.
  The instrument at the NERC MST Radar site is mounted on a pole at
approximately 1.9 m above ground level and at approximately 15 m to
the north of the site bungalow. Messages are recorded by a Network
Time Protocol enabled data logging computer together with the time (to
the nearest second) at which they arrived. Measurements of pressure,
temperature and relative humidity are generally in good agreement with
those from the Campbell Scientific climate data logger, which is
located approximately 50 m further north. Although the rain rates show
similar patterns to those measured by a tipping bucket raingauge, the
values from the WXT510 tend to have larger peak values and to be more
variable as a function of time. This is consistent with the fact that
the rates are evaluated over 1 rather than 10 minutes. The radar site
is located within an approximately ENE-WSW aligned valley which leads
to a strongly bimodal distribution of wind directions. Consequently
the wind information cannot be interpreted to be representative of the
larger-scale low-level flow. The wind data from the 10 m tower at
Frongoch farm, which is located 3 km to the west, are recommended for
this purpose.
"


List of Variable attribute values
float longitude ()
standard_name = "longitude"
long_name = "instrument longitude"
units = "degrees_east"
axis = "X"
comment = "
  The latitude and longitude of all instruments at the NERC MST Radar
site, located at Capel Dewi near Aberystwyth in the UK, relate to
British National Grid Reference SN637826. This is accurate to within
100 m. The altitude of the base of the MST Radar antenna array is
assumed (from the contours on an Ordnance Survey map) to be 50 m
above mean sea level. This is accurate to within 10 m. The altitude of
other instruments at the site are offset by their height above the
base of the antenna array. The heights of the instruments above ground
level refer to the local ground level, which is typically above the
altitude of the base of the antenna array.
"
float latitude ()
standard_name = "latitude"
long_name = "instrument latitude"
units = "degrees_north"
axis = "Y"
comment = "
  The latitude and longitude of all instruments at the NERC MST Radar
site, located at Capel Dewi near Aberystwyth in the UK, relate to
British National Grid Reference SN637826. This is accurate to within
100 m. The altitude of the base of the MST Radar antenna array is
assumed (from the contours on an Ordnance Survey map) to be 50 m
above mean sea level. This is accurate to within 10 m. The altitude of
other instruments at the site are offset by their height above the
base of the antenna array. The heights of the instruments above ground
level refer to the local ground level, which is typically above the
altitude of the base of the antenna array.
"
float altitude ()
standard_name = "altitude"
long_name = "instrument altitude above mean sea level"
units = "m"
axis = "Z"
comment = "
  The latitude and longitude of all instruments at the NERC MST Radar
site, located at Capel Dewi near Aberystwyth in the UK, relate to
British National Grid Reference SN637826. This is accurate to within
100 m. The altitude of the base of the MST Radar antenna array is
assumed (from the contours on an Ordnance Survey map) to be 50 m
above mean sea level. This is accurate to within 10 m. The altitude of
other instruments at the site are offset by their height above the
base of the antenna array. The heights of the instruments above ground
level refer to the local ground level, which is typically above the
altitude of the base of the antenna array.
"
float height ()
standard_name = "height"
long_name = "instrument height above the ground"
units = "m"
comment = "
  The latitude and longitude of all instruments at the NERC MST Radar
site, located at Capel Dewi near Aberystwyth in the UK, relate to
British National Grid Reference SN637826. This is accurate to within
100 m. The altitude of the base of the MST Radar antenna array is
assumed (from the contours on an Ordnance Survey map) to be 50 m
above mean sea level. This is accurate to within 10 m. The altitude of
other instruments at the site are offset by their height above the
base of the antenna array. The heights of the instruments above ground
level refer to the local ground level, which is typically above the
altitude of the base of the antenna array.
"
float time (time)
standard_name = "time"
long_name = "UTC on 2007-12-21"
units = "seconds since 2007-12-21 00:00:00 +00:00"
accuracy_details = "
  The data logging computer, which has Network Time Protocol enabled,
checks for new messages from the instrument once every second. These
messages are recorded together with the time of arrival to the nearest
second. This can lead to an apparent variability, of +/- 1 s, in the
intervals between regularly-spaced measurements.
"
resolution = 1.0f
axis = "T"
float rainfall_rate (time)
standard_name = "rainfall_rate"
long_name = "mean rainfall rate over the preceding 60 s"
units = "mm hour-1"
missing_value = 999.9f
_FillValue = 999.9f
accuracy_detailsdaily accumulations are accurate to within +/-5%= ""
resolution = 0.1f
coordinates = "latitude longitude altitude"
cell_methods = "time: mean (interval: 60 s)"
comment = "
  Within the first 60 s of a precipitation event, the rainfall and
hail rates are evaluated only over the period for which precipitation
is occurring. Otherwise they are evaluated over the preceding 60 s.
"
float rainfall_accumulation (time)
standard_name = "thickness_of_rainfall_amount"
long_name = "accumulation of rain since the last non-zero measurement"
units = "mm"
missing_value = 999.99f
_FillValue = 999.99f
accuracy_details = "daily accumulations are accurate to within +/-5%"
resolution = 0.01f
coordinates = "latitude longitude altitude"
cell_methods = "time: sum"
comment = "
  This is equivalent to the measurement made by a tipping bucket
raingauge, i.e. the accumulation of rain since the last non-zero
measurement.
"
float hail_rate (time)
standard_name = "precipitation_rate"
long_name = "mean hail rate over the preceding 60 s"
units = "hits cm-2 hour-1"
missing_value = 999.9f
_FillValue = 999.9f
accuracy_details = "unknown"
resolution = 0.1f
coordinates = "latitude longitude altitude"
cell_methods = "time: mean (interval: 60 s)"
comment = "
  Within the first 60 s of a precipitation event, the rainfall and
hail rates are evaluated only over the period for which precipitation
is occurring. Otherwise they are evaluated over the preceding 60 s.
"
float hail_accumulation (time)
long_name = "accumulation of hail since last since last non-zero measurement"
units = "hits cm-2"
missing_value = 999.9f
_FillValue = 999.9f
accuracy_details = "unknown"
resolution = 0.1f
coordinates = "latitude longitude altitude"
cell_methods = "time: sum"
comment = "
  This is equivalent to the measurement made by a tipping bucket
raingauge, i.e. the accumulation of hail since the last non-zero
measurement.
"

Internal Links:
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Gaining access to the data
A general description of netCDF file structure.
Page maintained by David Hooper
Last updated 4th June 2009