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7. Weather Control

Russian and American scientists have in the past tried to control the weather, for example by seeding clouds with chemicals to try to produce rain when and where it is needed. On the timescale of several decades, new weather control techniques may become feasible which would allow control of extreme weather such as hurricanes. It is considered one of the ways of adaptation to the changing climate and preventing disasters such as hurricanes, flood and droughts. Let us see how feasible it is by looking at some examples of experiments on weather control and the views and opinions of experts.
 

NewScientist.com news service, 25 July 2005
Oil on troubled waters may stop hurricanes
Zeeya Merali
Preventing hurricanes
The researchers suggest that, during a tropical storm, aeroplanes could deliver harmless surfactants to the ocean surface " reducing surface tension in water and stopping droplets from forming " perhaps preventing a hurricane developing.


But some climate physicists remain unconvinced. "I am very doubtful about this approach," says Julian Hunt at University College London, UK. He has studied turbulence both theoretically and in the laboratory and thinks that the high wind speeds are caused by an entirely different mechanism.


In a paper submitted this month to the Journal of Fluid Dynamics, Hunt suggests that variations in the turbulence between different regions of the hurricane cause sharp jumps in wind speed.


Chorin stresses that his team has not carried out experimental tests on the application of this work with tropical storms, but feels that it could be explored in the future.                                    

Things Asian, 22/06/2004
Rainmaking in China

"I would say that nearly every time it has rained in Beijing or northern China this year, man-made technologies to enhance precipitation have been used," Hu Zhijin, a cloud expert at the China Academy of Meteorological Sciences, told AFP. "Since April it has rained more times in Beijing than in previous years, but as far as the volume is concerned, we haven't had that much more."


Hu said rain enhancement technology was still an immature science. So far there are no analytical models or methodologies capable of producing data that conclusively shows the technology is effective.

A 2003 report by the US National Academy of Sciences also concluded that after over 30 years of trying, "there is still no convincing scientific proof of the efficacy of intentional weather modification efforts." Such reports, however, have not fazed Chinese officials, who, faced with growing water shortages, have ordered that man-made methods like cloud-seeding be used whenever and where ever clouds form over the nation's arid north.


CLOUD SEEDING TO AUGMENT RAINFALL TO FIGHT AGAINST DROUGHTS FLOODS AND HAIL STORMS
By Prof.T.Shivaji Rao

INDIAN EXPERIMENTS ON COLD CLOUDS
In fact Bombay Times in its Edition dt.23-6-1995 presents the successful artificial rain making experiments conducted by Shantilal Meckoni who successfully produced additional rainfall in Kutch region of Gujarat and in the Vaitarna and Tansa drinking water lakes of Bombay by sprinkling silver iodide over hot coke in ground generators.  This rain induction method involves placing silver iodide powder in a furnace to evaporate upwards into cooled water in the clouds into ice flakes that fall down to earth as heavy rainfall.  The parameters required for this experiment are: humidity must be more than 70%; wind velocity about 15kms per hour, cloud thickness must be about 10,000ft. and temperature in the cloud should be minus 5°C.  The experiment conducted at Tansa lake produced more than 70mm rain in 2 hours duration.  For each experiment just 250gms of silver iodide and a small amount of coke for the furnace is needed to maintain a temperature of about 1200°C  and blower is used for the purpose.  Meckoni says that Israel and Russian Governments conduct these experiments even when there is natural rainfall because they want to increase the water availability by making the clouds grow in size by merging with the neighbouring smaller clouds and also by processing more moisture from the updrafts created by the latent heat released during the experiments.  There are no side effects as the iodide disintegrates and the silver remains only in very minuscule quantities that are within the safe limits.  Meckoni learnt this science of rain induction from a visiting professor from Jerusalem University and chose Kutch, for his first experiments.

Meckoni and Shivaji Rao conducted cold cloud seeding by using ground generators once in July 1993 at the Osman Sagar lake at Hyderabad at the request of the AP State Government with successful results.  Similar experiments were conducted at Anantpur in July 1995 at the request of the State Government and the results were good and the rain fall for the year was obtained even before the end of South West monsoon.  Again Shivaji Rao conducted both warm cloud seeding by sprinkling common salt from an aircraft into the cumulus clouds and also used ground generators by sprinkling silver iodide over the very hot coals in the oven to seed the cold clouds during the middle of October at Visakhapatnam at the request of the Municipal Corporation.


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