Geoscience Reference
In-Depth Information
the Politecnico di Torino was involved in the development activities of this new network
starting from its early ideation stages (
Notarpietro et al.
[2005]).
The first designed scenario was specifically intended to cover narrow valleys within the Alps.
This was initially achieved by adopting a non-conventional vertical plane scanning strategy
with a fan beam slot waveguide antenna (1° beam width in the vertical plane, 25° beam width
along the valley). The initial implementation was simply designed to collect two low elevation
acquisitions with opposite directions along the valley plus a vertical sounding to evaluate the
vertical reflectivity profile (
Gabella et al.
[2008]). Then, this initial approach was extended to
collect radar sounding coming from the entire vertical plane. This kind of small low-cost radar
has been patented and is now sold with the name “wind-mill” mini-radar.
In a second stage, the more conventional horizontal scanning strategy was implemented to
cover wide planar areas with very high temporal resolution at a fixed, optimized elevation. This
suggested combining a number of short-range, low-cost radars into a network concept, to
obtain a set of similar small unattended units, tightly connected within a unified environment.
The result of the above approaches and suggestions is an unmaned, low-consumption, network
of low-cost, small, X-band radars. Adding up, the first prototypes, running since October 2006,
were installed on the Politecnico di Torino roof, sensing either the horizontal or the vertical
planes. During these years several progresses and modifications were made, leading to a
network of mini radars: one operated by the Aosta Valley Civil Protection (since March 2007)
and a vertical scanner unit (wind-mill) installed next to the glide path of the “Sandro Pertini”
Turin International Airport. Recently (autumn 2010), four horizontal scanners units were
installed in different areas of Sicily (see the web site http://meteoradar.polito.it/). At present,
seven small radars have been installed on the Italian territory and are successfully running. In
our approach, such network is capable of mapping storms with temporal resolution better than
1 min and focusing on the low-troposphere “gap” region. Such network has the potential to
complement the long-range radar networks in use today. In Chapters 3 and 4 the deployment of
small, low-cost, X-band radars will be presented for the following environments:
heavily populated areas (e.g. Palermo town and harbor, see Sec. 3.2 and 4.2; Turin town,
see Sec. 4.4);
specific dry and semi-arid regions where it is crucial to improve observation of low-
level meteorological phenomena (e.g. western Sicily, Sec 4.3)
deep valleys surrounded by high mountais region (e.g. Valle d'Aosta, see Sec. 3.1).
2.2 X-band, “short” wavelength technology for short-range monitoring
Cost, radiation safety issues and aesthetic issues motivate the use of small antennas and low-
power transmitters that could be installed on either low-cost towers or existing infrastructures
such as rooftops of existing buildings or telecommunication poles. This requires that the radars
are physically small and that the radiated power levels are low enough so as not to pose an
actual or perceived radiation safety hazard. We have opted for a very small parabolic antenna
(D = 0.6 m) which corresponds to a 3 dB cross-range spatial resolution of 1 km at 20 km range
(two third of the used range, which is 30 km). The antenna is hidden below a 1 m diameter
radome (Fig. 1, left picture) and rotates at ~120° per second using a single elevation.
One precipitation map is made available every minute by averaging 16 rotations (out of the
22 available) 9 consecutive rays and 2 range-bins, hence resulting in a total of 144 samples.
