The Story of Rain Part Two: Till the Last Drop

 |  September 1, 2015

Read The Story of Rain Part One here.

I was green with envy as I watched the planes land, until I saw the Citylife photographers, their faces featuring different hues of green, disembark. As a foreigner I wasn’t allowed to join the Royal Rain Makers on their mission today due to lack of proper paperwork, but judging from the complexions of my colleagues, I think it turned out for the best. It was no scenic ride, apparently the pilots of the two planes tasked to coax the clouds to rain had had a challenging flight.

Rain01It was July, the nation was in a panic over the lack of rains, and I was visiting the Royal Rainmaking Centre at Wing 41 to look into the issue.

After months of heat always comes the rain. Unless it doesn’t. Nature, no matter how hard we will it, never ceases to surprise us, or throw us into a flurry of panic, which is what happened to us this summer when the rains were MIA.

Last month Citylife explored the issue of drought and water resource management in Thailand and as promised, Part Two of the story aims to focus on efforts being made to restore the balance. As predicted in last month’s issue, by the time this magazine comes out, the rains will have come and the crisis (temporarily) over. However, one thing is for certain: the challenges Thailand faces due to its dependency on reliable rainfall isn’t any less significant because the skies have finally opened up.

This month we talk to the Department of Royal Rainmaking and Agricultural Aviation. In Thailand, rainmaking centres are found nationwide, and this year, having never needed it before, resulted in setting up the first centre in the south. The department’s rainmaking services seem to be ever increasing in demand; a process that was previously only needed in the dry months leading to monsoon season, has now become a year-round effort.

After making sure that our photographers were not going to stain the tarmac, I walked off the runway and into the snug office of the centre to meet its northern director, twenty-year veteran of the job, Nuenghatai Tantiplubthong.

Meet the Rainmakers
The small office was quiet, with a few support staff sitting at their computers, eating snacks and looking relaxed, belying the pressure I was soon to learn they were all under.

“We have a staff of 23 people on-site but the real number is close to 100,” Nuenghatai explained when I asked her to tell me about the workings of the centre. “Currently we have 34 pilots and support staff who fly every day possible. With Line and the internet, we don’t all need to be here. It is very intense right now because of the looming crisis and there is tension in the office every morning when we decide which clouds to seed for the day. Once decisions are made, we all get on with our jobs.”


Each morning the team comes together at the centre, or online, to study satellite images and data from Western Radars, which are used to check the conditions of the clouds. This information, paired with data sent from the Royal Irrigation Department, Meteorological Department and the Ground Water Resource department, as well as requests by farmers and local authorities, is used in decisions made by the Royal Rainmaking staff on which clouds to work on for the day. Each flight is also recorded and their attack areas posted publically online daily on the royal rainmaking website.

According to recent logs, up to 22 flights can be carried out on any given day. An individual seeding flight can cost upwards of 230,000 baht, though multiple runs can drive the per flight cost down. But even so, the business of making rain is far from cheap, and its results not guaranteed. Captain Rawi Hachaturat, a pilot I also talked to, explained that it takes much more than just choosing a cloud and seeding it. “Our flight times really depend on how high we must fly in relation to the other aircraft,” he said. “We have to be in constant communication with air traffic control to avoid crashes. If we fly a Sandwich or Super Sandwich, we must also talk to the other rainmaking planes, if I turn, I must tell them so we can move together – both to avoid crashes, and to ensure the seeding is a success.”

Getting Technical
Every day the department receives calls from local farmers or their local representatives angrily demanding or desperately pleading for help to induce rain. Over 400 individual farmers had called thousands of times this year by the time we talked to the centre. It appeared that farmers believed the rainmaking centre to be their last ditch hope at getting some rainfall. Previously farmers could rely on the Irrigation Office, but with their supply of water reaching critical levels, the responsibility had shifted to the rainmakers.

When His Majesty the King visited drought-stricken Isaan over 45 years ago, his concern led him to work towards adjusting a then-existing technology, initially developed in less humid and colder countries, to fit Thailand’s more humid climes. Previously, cloud seeding was possible for only supercooled clouds, dense with water droplets at temperatures under 0 degrees Celsius.

His majesty’s patented six point process, cutely nicknamed the Sandwich and Super Sandwich, has been recognised as an effective cloud seeding method for hotter climates.

According to Nuenghatai, the techniques are effective, but only under the right elements. Rainmaking basically involves the ‘seeding’ of natural clouds to increase their density and induce heavier rainfall.

Put simply, rainmaking increases the chance of rain by encouraging the amount of particles and moisture in the air to join together via the use of ‘seeding agents’ that work as ‘cloud condensation nuclei’.

Humidity, temperature, the speed and direction of winds, cloud physics, and the amounts of chemicals released at any one time, can all affect the outcome.

The six step process for seeding clouds with temperatures higher than 0 degrees Celsius is used almost every day in Thailand. Each step can be performed independently depending on the status of the clouds and their formations at any given time, but each step continues from the last to ensure greater success.

Triggering: When the skies are clear and there is relative humidity of over 60%, salt is released into the skies at around 10,000 feet to work as cloud condensation nuclei. Water droplets in the air are attracted to the salt and cloud formation is more likely to happen.

Fattening and Moving: When clouds begin to form at around 7,000 to 10,000 feet, calcium chloride, which is highly soluble in water, is released at 8,000 feet, encouraging top growth, where the cloud extends to a height of around 15,000 feet.
This is when the clouds begin to churn and become elongated_ a natural process in cloud growth.

Attacking with Sandwich Technique: During the churning process, two planes release two chemicals at 45 degrees from one another. This is what is known as the King’s Sandwich technology and works specifically for warm clouds. Here salt is released at the top of the cloud and urea is released at the bottom of the cloud. This condenses and cools the cloud base, promoting large water droplets that will fall as rain.

Enhancing: During the first stages of induced rainfall, dry ice can be released under the cloud, keeping the atmosphere cool enough under the cloud to maintain rainfall and further increase the size of the rain droplets.

Later additions to the King’s patented rainmaking technology include methods used for cold clouds at below 0 degrees Celsius.

Attacking with Glasciogenic Seeding Technique (Used after Step 2): This will be used when the clouds targeted are supercool, with water droplets in a liquid state below 0 degrees Celsius. Here, silver iodide is dumped into the cloud from above, usually around 20,000 feet. This increases the number of ice nuclei, promoting growth and initiating rainfall.

Attacking with Super Sandwich Technique (Used after Step 2): This method is used when the clouds are still churning and there are both cool and warm sections to the cloud formation. Here, a combination of the Sandwich and Glasciogenic Seeding techniques are used, with three planes covering all bases, ensuring the cloud is seeded by either method. This involves silver iodide being dumped into the cloud from above via the Glasciogenic Seeding technique along with salt and urea being released following the Sandwich Technique.


For those concerned about toxicity and whether the chemicals are harmful, rest assured, said Neunthatai, the toxicity is nominal. Natural rain water today, more so than in the past, is slightly acidic at around 5.5 pH. Rain induced by seeding chemicals maintain an almost exact level of pH. Also, despite silver iodide having a mild health hazard rating of two, studies conducted in Thailand and abroad show negligible environmental and health impacts from seeded rain, with one report comparing the exposure to silver as less than what we would receive from a single tooth filling. The more successful the seed, the more diluted the chemicals become too, resulting in the majority of chemicals to be so dissipated into the atmosphere, clouds, and rainfall that no serious effects could come of them.

Between March 1st and August 20th, the rainmakers nationwide flew a whopping 4,042 flights, covering over 5,500 air hours. Recently Prime Minister Prayuth Chan-ocha praised the rainmakers, especially the Chiang Mai and Nakhon Sawan centres, both of which, he says, have worked tirelessly to seed clouds resulting in widespread rains releasing an estimated 1,204 million cubic metres of water.

The Challenges
The techniques listed above, if performed accurately, do have the ability to increase cloud density and encourage rainfall. However, according to Nuenghatai, fewer clouds are forming each year which makes these processes less effective and requires much more effort, pushing the costs higher and higher each year.

Nuenghatai does not sit comfortably on her laurels. “There is a noticeable change in the climate in Thailand now,” she explains. “With more pollution, fewer trees and more open soil surfaces, natural cloud formation is becoming less common. In reference to the annual haze, Nuenghatai also points out that the severe level of pollution is causing water molecules to become attached and absorbed by the pollution particles before they get a chance to join with other molecules to form clouds. Air blowing over the mountains that surround the city warms, then traps and compresses the cool air over the city in what is referred to as subsidence inversion.

Everything in that air, including vehicle emissions, smog and the all too common smoke from slash and burn farming, is trapped over Chiang Mai and the surrounding area, becoming a barrier that stops almost all water molecules from naturally forming into clouds.

She has also noticed a sharp increase in demands by farmers and their representatives in previous years. “This year recorded the hottest temperature in the north at 39.6 degrees Celsius,” claimed Nuenghatai. “After 20 years of working with the Royal Rainmakers, things have changed so much. When I was younger, Nimbostratus clouds were everywhere, and they were so easy to seed. They would take just one round of seeding for them to produce lots of rain. Now there are no more Nimbostratus clouds forming, and for each cloud that we seed, we need to seed many times before we see any results. Often we work on a cloud for days, slowly building it up flight after flight.”

“This year is the first time we have seen summer in monsoon time,” continued Nuenghatai. “Clouds are forming less and forming higher; it’s getting too hot for rain to fall.” With the climate change becoming more and more noticeable, Nuenghatai can see the changes first hand.


“One day of rainmaking will not work anymore,” Nuenghatai said. “The environment is changing and we may have to leave rainmaking to nature once again.” Prime Minister Prayuth Chan-ocha has recently admitted that more needs to be done to help save water, prompting communities to dig wells and build reservoirs in order to create long-term solutions for water management and drought mitigation. As the costs of cloud seeding becomes more prohibitive, Thailand needs to look down to terra firma for solutions, rather than only expecting them to come from on high.

Water shortages are becoming a global concern. Thailand has until now escaped unscathed, but with more and more erratic weather patterns, with the rapid deforestation, and with farm practices that over burden the water management resources, we can no longer rely on the Royal Rainmakers to generate enough rain to sustain all of our agricultural needs. Soon there will be stories of floods and the drought will be relegated to a distant memory. Until next year.

For more information on the Royal Rainmakers, and data about their flights, check out: