SYDNEY • Circling thousands of feet above Tasmania's farmland in a light aircraft, Ms Christina Nebel prepares to release tiny chemical particles as part of a cloud-seeding scheme estimated to have helped boost rainfall on the Australian island by at least 5 per cent.

The programme is one of a handful globally that are riding a wave of renewed interest in the decades- old technology, as drought hits places ranging from the United States to the Philippines, with the spectre of a strong El Nino weather pattern threatening worse to come.

"We are looking for fronts crossing Tasmania," said Ms Nebel, a cloud-seeding officer at renewable energy producer Hydro Tasmania.

Tasmania is blessed with near- perfect conditions for the process, with clouds containing a large amount of cold water vapour whipping in off the Southern Ocean.

This means the scale of success of its programme, which has its roots in the 1960s, could be difficult to replicate elsewhere.

Nonetheless, atmospheric experts said the technology is enjoying a renewed emphasis as governments fret over scorching weather and as populations grow.

"What is driving the attention is that winter cloud seeding holds some promise and, in many places, including the western US, water shortages are becoming severe," said Professor Terry Deshler from the University of Wyoming.

While many of the world's cloud- seeding programmes are small and unlikely to have more than a limited impact, China has a large-scale initiative in place. The nation launched its "human affected weather" programme in 1958 and has done extensive research in cloud seeding.

It aims to induce more than 60 billion cubic metres of additional rain each year by 2020 using the technique, as it looks to fight chronic water shortages. REUTERS