Most downpurs occurred at the peak of summer in July and August when there were normally no rains. People in Abu Dhabi were baffled by the rainfall, which sometimes turned into hail and included gales and lightning.
The scientists were working secretly for United Arab Emirates President Sheikh Khalifa bin Zayed Al Nahyan, the Daily Mail reported. They were using giant ionisers, shaped like stripped down lampshades on steel poles, to generate fields of negatively charged particles.
The Metro System scientists used ionisers to produce negatively charged particles called electrons. These have a natural tendency to attach to tiny specks of dust which are ever-present in the atmosphere in the desert-regions.
These are then carried up from the emitters by convection - upward currents of air generated by the heat release from sunlight as it hits the ground. Once the dust particles reach the right height for cloud formation, the charges will attract water molecules floating in the air, which then start to condense around them.
If there is sufficient moisture in the air, it induces billions of droplets to form which finally means cloud and rain. In a confidential company video, project incharge Helmut Fluhrer, of Metro Systems International, boasted of the success. Fluhrer said: "We have achieved a number of rainfalls."
Last June, Metro Systems built five ionising sites each with 20 emitters, which can send trillions of cloud-forming ions into the atmosphere.