Windprofilers use radar techniques to produce radio scatter from weak
irregularities in the air above them, and utilize this information to determine upper
level wind speeds and directions. They may use either "Doppler beam pointing methods"
or "spaced antenna methods", using arrays of antennas.
The WindTtracker radar is much more than a windprofiler radar. Whereas traditional systems
can measure horizontal and vertical winds, and power levels, the WindTtracker radar also
measures a variety of other parameters which have never been fully utilized before. We will
discuss these shortly.
It also utilizes a hybrid of Doppler-beam-swinging (DBS) and spaced-antenna (SA) techniques to optimize its performance. Above 1.5 km altitude, DBS methods are used, in order
to take full advantage of the large area of the antenna array. We produce a two-way beam half-power half-width of less than 1.7, allowing high gain and optimal
signal returns. Below 1.5 km, we offer an additional spaced antenna option which
permits winds to be determined down to 400 metres altitude and even lower in some cases.
We have developed very detailed procedures for both extraction of the wind and for its
later analysis. Our spectral extraction procedures are among the most detailed
in existence, permitting us to isolate spectral peaks corresponding to wind motions
with good discrimination. Because of this excellent discrimination, we can obtain useful winds to 16 km altitude and above using a 40 kW radar. We use a 5-beam system, which is very important for discriminating non-atmospheric echoes. Our quality control procedures are very thorough, and we take considerable care to remove outliers and contaminants. Our system also
utilizes a graduated vertical resolution, using 500 metre resolution at 1.5 km and gradually
increasing to 1 km at the higher altitudes.
One of our key new parameters is the strength of turbulence (energy dissipation rate),
which is displayed as a function of height and time for scientific research
applications. Indeed the name "WindTtracker"
originates from the fact that this radar measures both Winds and
Turbulence and can be used to track their values viz. Wind and
Turbulence tracker. We take great care to remove so-called
"beam-broadening" effects in our measurements of turbulence, utilizing a detailed 4-dimensional numerical computer model
which can deal with any type of wind profile structure. In the past, the energy
dissipation rate has not often been calculated, and it is almost never displayed
as a standard parameter. Previous calculations used simplistic beam-broadening models
which assume either a constant wind as a function of height, or a linear wind shear. The
effect of the pulse-length is rarely properly considered. Our new model generalizes all
these concepts, and yet still produces estimates of the strengths of turbulence
in close to real time.
In addition, we also display the atmospheric anisotropy as a standard parameter. Again,
this is quite new. The anisotropy parameter indicates information about the nature
of the atmospheric scatterers, and this can tell us information about the atmospheric
condition. For example, in conditions of strong convection, the scatterers become
more isotropic, and this can often be a precursor to convectively generated clouds and
subsequent precipitation. When the atmosphere is very stable vertically, or when strong
wind shears exist as a function of height, the scatterers are more anisotropic, which
can be seen as a reduction of the powers on the off-vertical beams relative to the
power on the vertical beam.
Because we use a 5-beam system, we can also determine other important atmospheric
parameters like momentum fluxes and gravity wave activity - again parameters which
are not traditionally measured on a regular basis.
Our system also regularly monitors the height of the tropopause, using a variety of
different and complementary techniques.
You can see some examples of the graphics produced with our system in the gallery (see tablets
on the left). In addition, if you wish to see our system in real-time operation, please go
the McGill VHF WindTtracker radar,
where you will see some of our typical outputs produced from the radar
which we have installed for McGill University at their MacDonald campus. These data
products are updated on an hourly basis.
Web page creation and design by David Hocking -- harm001@ToughGuy.net