Rain Making: Urgent Action Needed



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For Cumulonimbus (rain) clouds to form there must be three things. Moisture, an unstable atmosphere, and some sort of trigger action to like turbulence or orographic lift to start the process going. Even if moisture is present, unless there are sufficient nuclei in the form of dust, smoke, salt crystals, for water vapour to condense on, within the cloud, it is useless. When the water vapour condenses to liquid it releases Latent Heat (remember your physics?), which make the cloud warmer than the ambient air, making it build up and rise to form a massive Cumulonimbus cloud, sometimes rising up to 40,000 or even 50,000 ft. in the tropics. The spraying of suitable nuclei such as Silver Iodide or Salt crystals inside or above the cloud by aircraft, is what cloud seeding is about. There are three stages of a Cumulonimbus cloud. The Developing stage, Mature stage and Dissipating stage.


On 7th September morning, I flew from Ratmalana to Sigiriya and back in a light Cessna aircraft. It was extremely turbulent (mechanical action) and there was a layer of 'fair weather' cumulous cloud from 5000ft to 7000ft all the way along our route. While flying inside a 'Developing' and 'Mature' Cumulonimbus cloud is extremely dangerous and foolhardy, flying inside 'fair weather' cumulous clouds can be safely done by light aircraft. (In fact light aircraft could withstand higher amount of 'G' forces than big passenger jets.) To me it looked as the clouds were ripe for seeding. I have been 'cloud hopping' for almost fifty years.


We read in the newspapers that there were some Thai experts advising the Government on cloud seeding. Who are they? And what Government Department are they advising? None of them were in the air, that day, looking for potential rain clouds. Have they gone back? I believe that to combat the prevailing drought we need to have a home grown team, with local scientists, pilots and suitable aircraft and equipment, which are available with the SLAF or the private sector.


What upsets me most is that we sit and theorize about the 'pros' and 'cons' of rain making, from ground, without getting airborne and experimenting with the resources we have. India is doing it in a big way. It is reliably learnt that when India requested Sri Lanka to allow their rain making aircraft to park in the Island in between flights a few years ago, certain short sighted officials had refused permission. Had that happened, our scientists and pilots could have gained from the experience.


Technology has improved so much that we now have on board Global Positioning Systems (GPS) that could show us the cloud's location and a wind read out to show where the cloud is going to. This will enable us to selectively seed the clouds. We could experiment in a small way and gain some valuable experience. After all, the proof of the pudding is in its eating.


CAPT. G A FERNANDO


 
 
 
 
 
 
 
 
 
 
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