Maleny Weather

Listening to the news yesterday, you might have been forgiven for thinking it was April 1, not March 30th

The BBC soberly reported that scientists were considering using wind-driven ships to spray salt into the air to make clouds whiter so they could reflect more solar energy and help reduce global warming.

Stranger still, it turns out this is just one of the ingenious ideas discussed in a special edition of the Royal Society’s journal devoted entirely to the pros and cons of geo-engineering, large-scale interventions to help modify the Earth’s climate.

Others include blocking sunlight by floating mirrors in space, using rockets to spray sulphur into the upper atmosphere, and seeding the oceans with iron to trigger plankton blooms that would draw carbon from the water before locking it away on the sea bed as the plankton died and sank to the bottom.

The cloud-seeding idea is explored in a section called “Sea-going hardware for the cloud albedo method of reversing global warming”.

It explains: “Wind-driven spray vessels will sail back and forth perpendicular to the local prevailing wind and release micron-sized drops of seawater into the turbulent boundary layer beneath marine stratocumulus clouds. The combination of wind and vessel movements will treat a large area of sky.

“When residues left after drop evaporation reach cloud level they will provide many new cloud condensation nuclei giving more but smaller drops and so will increase the cloud albedo to reflect solar energy back out to space.”

But before you think it’s ok to leave all the lights on and take your 4 x 4 out for a spin, the Royal Society makes it clear such schemes would only tackle the symptoms, not solve the problem.

“None of these technologies will provide a ‘get out of jail free card’,” said Martin Rees, President of the Royal Society. “They must not divert attention away from international efforts to reduce emissions of greenhouse gases.”

Flash floods happen suddenly (hence the name), forming in less than six hours. This sets them apart from “regular” floods, such as river floods, which can often be predicted days in advance. They are caused when a heavy rain falls over low-lying areas, especially when the soil is already saturated. They happen when rainfall intensity and duration match up, in a very bad way.

More than half the fatalities happen when people try to cross flooded intersections in their cars. This is because people are generally not very good at judging the depth and danger of flooded streets. (They can’t actually see the roadway surface, which might be a big deep hole.) While two feet of water doesn’t seem like much at all, especially if you are safely inside a big, heavy car, it is enough to carry you and the car away. (Another fact we tend to forget: cars are buoyant.)

According to the NOAA , “Water weighs 62.4 lbs. per cubic foot [1,010 kg per cubic meter] and typically flows downstream at 6 to 12 miles an hour [10 to 20 kph]. When a vehicle stalls in the water, the water’s momentum is transferred to the car. For each foot the water rises, 500 lbs. [226 kg] of lateral force are applied to the car. But the biggest factor is buoyancy. For each foot the water rises up the side of the car, the car displaces 1,500 lbs. of water. [For each meter the water rise up the side of the car, the car displaces 2,040 kgs of water.] In effect, the car weighs 1,500 lbs. [2,040 kg] less for each foot [meter] the water rises.”

Do not be tempted to drive across a flooded roadway.(”Don’t drown; turn around.”) If you find your vehicle stalled in a flooded road way, leave it and seek higher ground. (”Better wet than dead.”)

This video on YouTube of a flash flood in Merriwa, NSW, shows just how quickly a flash flood can occur.

A wetter than normal season is favoured for south-east Queensland, with temperatures cooler than normal according to the Bureau of Meteorology

At least 35 people have been killed and hundreds of houses are underwater after a dam burst near the Indonesian capital Jakarta. An emergency services spokesman says the dam on the south-western outskirts of the capital burst in the early hours of the morning after heavy rain

Over the past week there was little change in the weather on the Range. A high of 1025hPa in the Tasman Sea and a deep low in the Coral Sea, that for a short while became TC “Jaspin”, brought southerly maritime trade winds on to our shores. Days were dry and humid with temperatures in the mid twenties. It was not until Saturday that winds strengthened from an interaction between the high in the Tasman Sea and the ex-TC “Jaspin”. Sunshine and showers, heavy at times, were the order of the day. Total week’s rainfall came to 6.8 mm, bringing the month’s total to-date to 209.8 mm. The week’s evaporation was 11.6 mm and Bright Sunshine shone for 50.8 hours.