O Alentejo tem um déficit hídrico recorrente. Impedir a chuva porque calha numa altura inconveniente para alguém... Para mim, está tudo dito. Aqui em Nisa as charcas estão quase todas secas, mas esta até é uma região de aquíferos bons. Noutros sítios não há essa sorte.
Mas o objectivo aqui era não estragar as vinhas... Do modo que isto vai, algum dia quando se prevê tempestades põe-se tudo a "disparar" para o ar e será muito mau para os Storm Chasers
De qualquer forma continuo muito céptico, penso que os tipos nos EUA para impedir aquele granizo extremo que eles tem (muito mais violento que aqui) então gastariam metade do arsenal militar em Oklahoma em vez de guerras espalhadas pelo mundo.
Usually, the number of ice crystals in the cloud is small and, upon the existence of appropriate conditions, they grow rapidly to hailstones with large sizes.
The most popular hail suppression concepts are:
Seeding increases significantly the ice embryos concentration so that the artificial and natural ice particles compete with each other for available liquid water. The supercooled water redistributes between all ice embryos and thus resulting hailstones are small. Falling to the ground, they melt to rain or sleet.
Seeding accelerates precipitation development, resulting in the “rainout”of still small hydrometeors from convective turrets that have not yet developed updrafts strong enough to support the growth of hail. Thus, the cloud supercooled water content (from which hail might otherwise grow) is reduced.
Seeding accelerates hail embryos growth at lower level in the cloud, where liquid water content is smaller and updrafts are weaker. Then the hail falls out of the cloud both in smaller sizes and earlier than if that would have taken place naturally.
ADMINISTRATIVE ORGANIZATION OF THE PROJECTS
The ANELFA was born in 1951. It is a nonprofit association federating a dozen of regional entities
(département) located in hail damaged areas. Each local
association collects the funding for its participation to the
ANELFA project. The members of the local associations
and of the ANELFA are politicians, agronomists, and
leaders of agricultural organizations. In the départements
covered by this association, 660 seeding stations are spread
out in local networks with an odd 10 km mesh. The area is
distributed over four regions and represents a total of
SPAIN: The “Consorcio por la Lucha Antigranizo de
Aragon” has the responsibility of managing the seeding
operations. The Project is developed in two areas situated in
Zaragoza and Teruel (Ebro Valley area).The first area
named Valjalón, is in a mountainous region with frequent
hailstorms and comprises 30 remote ground generators with
an odd 20 km mesh. This target area represents about
6,500 km². The second area, named Bajo Aragón, is placed
in a part of Teruel and Zaragoza over a mountainous area
and has 21 remote ground generators for seeding operations.
The protected area is about 2500 km².
SEEDING AND MEASUREMENTS
Each station is equipped with a manual
vortex ground generator which burns a 1% solution of AgI-
0.5 NaI in acetone. The hail forecast is made by MétéoFrance according to a special agreement with the ANELFA.
The non-randomized seeding begins at least 3 hours before
forecast hailfalls and lasts until the end of the risk period.
There are some 20 days with hail warning per year for each
local network, an event lasting around 10 hours.
In the ten past years, the 660 stations have released a
mean amount o
Since 1988, more than 1000 hailpads with a density of 1
hailpad every 8 km have been recording the physical
parameters of hailfalls in the area.
Each station is equipped with an automatic
ground generator which burns a 1.2 % solution of AgI-0.5
NaI in acetone. The hail forecast is made by the University
of León which is in charge of the scientific aspect of the
project. The non-randomized seeding begins at least 1 hour
before forecast hailfalls and lasts until the end of the risk
period. The seeding period starts around May 15 and ends
by September 30. There are about 50 days with hail warning
per campaign. These past years, stations have released a
mean amount of 250 kg of silver iodide per hail season.
100 hailpads with a density of 1 hailpad every 5 km are
distributed homogeneously in the area and the network was
set up in 2003.
A 5 cm radar in Zaragoza is used both for forecast and
Hail prevention (severe storm suppression in fact) as part of Natural Disaster reduction activity is of great public and economic importance. The latest scientific and technical achievements of Russian rocket seeding technology are realised in an Operational Hail Protection and Research Program in the Province of Mendoza, Argentina. Digitised MRL-5 weather radars (X and S bands) operate under a Computer software control and allow the recording of storm data on CDs for further reviewing of the operations. Software calculates the seeding area, how many rockets should be launched for covering the seeding area, which launching sites are going to intervene in the action, as well as the azimuth angels for firing off the rockets. All these decisions could be adjusted by the operator, depending on his own experience and skill.
The Bulgarian hail suppression system was set up in 1968
as a structure of the Ministry of Agriculture. The Agency
carries out its activities by analysing and monitoring the
weather conditions using MRL5-IRIS Doppler radars and
In Bulgaria, the method of delivery of reagent - artificial
ice-forming nucleus (AgI) in clouds by rockets has been
adopted. It enables the direct and continuous dispersion of
reagent in seeding cloud areas at regular intervals during
the whole period of hail danger.
The overall hail suppression activity is carried out by the
RAPIRA system. The system is designed to process and
display the weather radar information from MRL5-IRIS, to
process the aerological sounding data, to command and
control the cloud seeding with seeding reagent and to
command the anti-hail rockets launching.
Real time meteorological radar information is transferred
to the National Civil Protection Service and the Air Force.
In order to prevent hail damages, it is necessary to
transform the dangerous convective clouds so as not to
allow the formation of large hailstones.
Seeding increases significantly the ice embryos
concentration so that the artificial and natural ice particles
compete with each other for available liquid water. The
supercooled water redistributes between all ice embryos
and thus resulting hailstones are small. Falling to the
ground, they melt to rain or sleet – this is called beneficial
MRL5-IRIS is a modern Doppler radar system for automatic
volumetric scanning of the atmosphere and data archiving.
The system includes three radar stations and an
information centre in Sofia, fitted up with IRIS Analysis and
6 remote posts with IRIS Display. Real time volumetric
radar information is transmitted to other command posts
and the information centre in Sofia.
Gerofil, pronto, já estive a ler mais uma coisas, e não seriam foguetes que dissipam tempestades como inicialmente destes a entender mas semeadura de nuvens (cloud-seeding) com iodeto de prata ou gelo seco.
Impedir que chova já por si, seria muito complicado, quanto mais evitar cair granizo.. Posso estar enganado, mas a mim parece-me uma vtipo banha da cobra! É que simplesmente não estamos falando de litros ou quilos de gelo, falamos de toneladas e toneladas, enfim esqueçam lá isso!!