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THE NERC MST RADAR FACILITY AT ABERYSTWYTH
FILE FORMAT FOR VAISALA WXT510 PRECIP DATA
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:
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:
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
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
char institution = "
Data recorded by the Natural Environment Research Council (NERC)
Mesosphere-Stratosphere-Troposphere (MST) Radar Facility at Aberystwyth -
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 -
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
More detailed information about the data is available at
The manufacturer's details about the instrument can be found at
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:
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
List of Variable attribute values
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Last updated 4th June 2009