Cloud seeding : Making it rain
If you were among the thousands caught by surprise — minus umbrella — in the unseasonal downpours last fortnight wondering what is going on with the weather, you are not alone.
From the beginning of April till now, more than 47 cloud seeding operations — manmade interference to enhance rainfall — have taken place in the UAE. The most concentrated of these, 85 per cent, according to sources Khaleej Times spoke to at the National Centre for Meteorology and Seismology (NCMS), have taken place in the last two weeks of April — in an effort to bolster water supplies. And already in 2013, cloud seeding occurrences are 30 per cent more than the entire previous year.
What is cloud seeding?
To understand in detail exactly how cloud seeding works, a familiarity with science and geography is helpful. But simply put, cloud seeding is the injection of salt crystals into puffy (cumulus) clouds to create more rain. And once clouds are injected — by planes which go up to the clouds and launch salt flares into them — and the droplets grow bigger, a collision of droplets happens. This is called coalescence. When the droplets become too big and moisture can no longer be retained, the droplets come down as rain. The ground only receives rain 20 minutes after each seeding event. And how heavily it rains, how heavy a downpour we experience, depends not just on the size of the cloud but crucially also on air pressure.
Now for all of these 47 operations that took place in April, the stage was already set. It was cloudy to begin with. And unstable weather conditions that lead to cloud cover are a major prerequisite to conduct any cloud seeding operation.
The presence of clouds makes it possible for planes to go up into the sky and launch iodine into fluffy cumulus clouds, as flat clouds do not work. As against some popular misconceptions, cloud seeding is not the creation of rain which is not in the control of the meteorological department. It’s actually the enhancement of rainfall, for which cloud cover must naturally exist.
The distinction is crucial to understand the effects of weather manipulation. And while the increased rainfall is not solely due to cloud seeding, Abu Dhabi – Al Guha, 100 kilometres south of Al Ain – had 136 millimetres of rain in April, itself unusual for this time of the year. According to experts at the NCMS, the arid country, which has a restricted water supply, is suffering from a dearth of water resources, which is why the government is anxious to increase cloud seeding operations so more water can be collected.
The jury is still out on how much of that rain is due to cloud seeding, while the cost of these operations is allegedly not for public consumption.
A Brief History
Cloud seeding in the UAE began 10 years ago when the government, together with the National Center of the Atmospheric Research (NCAR) in the USA and the University of the Witwatersrand in South Africa, started a programme to introduce cloud seeding technology. And thus began what is called rainfall enhancement via hygroscopic seeding. So far, in terms of seeding events, as they are called, this year has been the busiest.
To cloud seed, as explained by a meteorologist at the NCMS: “You need clouds that have bumpiness”. Bumpiness in the clouds is good, he says, adding that’s what they look for. It’s like an instinct before embarking on an operation.
“A good updraft will cause bumpiness.” So when you’re in flight and you experience turbulence mid-air, those conditions (called ‘clean air turbulence’) can be favourable to seeding.
The crystals injected into clouds are potassium chloride and sodium chloride. The phenomenon is akin to leaving table salt on your kitchen counter overnight and a day more. If you pay attention, you will see the salt left on the counter will turn dark and wet, because of the accumulated moisture and dirt from the kitchen air. The moisture is attracted to salt, and the principle works the same way for the fluffy clouds.
To conduct these operations, four planes are currently used to fire flares into the clouds and disperse tiny crystals that will pull moisture to them and cause puddles on the ground.
Most people are curious about the concept of cloud seeding but there is little clarity regarding what exactly the concept is, says a climate change official at the NCMS.
The coming days are not seen as reason to worry. As in summer months evidently, as many as four days a week are forecasted to have “frequent formations of clouds, and this is good news for us as it encourages seeding operations,” especially along The Hajar mountains in northeastern Oman and eastern areas of the UAE.
Cloud seeding history
The country has the largest cloud seeding system in the world. To clear the air of pollution, cloud seeding was used in Beijing just before the 2008 Olympics. In February 2009, the snowfall in Beijing lasted for approximately three days and led to the closure of 12 main roads around Beijing. Beijing has claimed it had its earliest snowfall in 1987 due to cloud seeding.
Cloud seeding operations have been conducted by the government of Tamil Nadu since the 1980s, in times of severe drought. About a decade ago both the Karnataka and Maharashtra governments conducted cloud seeding.
In the United States, cloud seeding is used to increase precipitation in areas experiencing drought, to reduce the size of hailstones that form in thunderstorms, and to reduce the amount of fog in and around airports.
Cloud seeding began in France during the 1950s with the intent of reducing hail damage to crops. A similar project is on in Spain. The success of the French programme was supported by insurance data. In Germany, civic engagement societies organise cloud seeding on a region level.
The seeding activities over central and western Tasmania since the 1960s appear to have been successful, with some areas achieving rainfall increases as high as 30 per cent in autumn.
The cloud seeding project, which began in July 2010 and cost $ 11 million has been successful in creating rainstorms in Dubai and Abu Dhabi.
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