Richa Sharma/IANS

New Delhi, Jun 29: If it doesn't rain, it might still pour! That's what some Indian scientists are hoping to achieve with a national cloud seeding programme at a time when there's uncertainty about the arrival and intensity of the monsoon this year.

Scientists at the Pune-based Indian Institute of Tropical Meteorology (IITM) are set to create artificial rain with this programme.

Cloud seeding is the process of introducing chemicals (either dry ice or more commonly, silver iodide aerosols, potassium and sodium chloride) into the upper part of clouds to try to stimulate the precipitation process and get rain.

"Scientists at the IITM have started the experiment to create artificial rain. It is a three-year project launched in May and, based on the feedback, the government will take a call on its implementation," Shailesh Nayak, secretary at the Earth Sciences Ministry, told IANS.

The IITM, a premier research institute under the government, launched the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (Caipeex) on May 17, 2009, to study cloud seeding.

"It is a national programme which will help in providing a scientific basis for the operational way of cloud-seeding. For the last 20 years we have been experimentally undertaking cloud-seeding activity successfully and an 11-year cloud seeding project between 1973 and 1984 showed increase in rainfall by 20 percent," J.R. Kulkarni, programme manager at Caipeex, told IANS.

The experiment will be carried out in three phases. During the first phase (May-October), the scientists have been observing different monsoon clouds over the country using an aircraft with special equipment.

"The aircraft is equipped with a special instrument to measure cloud parameters - temperature, wind, liquid water droplets - and aerosol background. This data will provide us with properties of clouds in different parts of the country," said Kulkarni.

The IIMT has already studied clouds in western and northern parts of India and the team is likely to finish the southern region by June end.

During the second phase (June-September 2010), random cloud seeding experiments will be carried out, using the aircraft equipped for seeding and the one containing the special equipment.

"Based on the properties of clouds, we will start the seeding programme across India. The seeding aircraft will spray hygroscopic particles (salts) that can broaden water droplets in clouds and hasten the onset of precipitation formation," said Kulkarni.

In the third phase (2011-12), scientists will measure and analyse the seeding impact.

"A dense network of automatic rain gauges will be installed in the experimental area to measure the rainfall. Rain water samples will be collected from the seeded and non-seeded clouds. The chemical analysis of rain water samples will be carried out to understand the effect of seeding on the precipitated water," he said.

"The experiment will give us an idea which areas are conducive for cloud-seeding and the amount of increase in rainfall after the experiment," he added.

Many other organisations, including the Indian Institute of Technology-Kanpur, the National Aerospace Laboratory, Bangalore, the Indian Air Force and the Indian Navy, are participating in the project.

China presently has the largest cloud seeding system in the world. It used cloud seeding in Beijing just before the 2008 Olympic Games in order to clear the air of pollution. In February 2009, China also used iodide sticks to artificially induce snowfall over Beijing after four months of drought.

A total of 24 countries currently practse weather modification operationally.