Investigating thunderstorms to better predict when they might strike
Thunder claps, lightning bolts, wind and hail – all the opera of an ordinary thunderstorm – aren't entirely understood by climate scientists. As the planet warms, thunderstorms are expected to become more intense, but no one can say for certain how the winds will blow.
Climate scientist Dr Martin Singh intends to find out, with the help of Australian Research Council funding.
“I'm concentrating on those small-scale thunderstorms that might be a few kilometres across," he said. "When you look out your window and you see lightning and a big cloud – that’s the kind of thing.”
He's particularly interested in tropical and equatorial thunderstorms – these often take place in monsoon season. Monsoons are thousands of kilometres across, and responsible for helping feed more than two billion people; individual thunderstorms within the monsoon influence its behaviour, but their impact isn't well understood.
“Global climate models don’t see thunderstorms,” Dr Singh explains. “The way the models work, you chop up the world into boxes, and you solve a set of equations for each box that determine how the atmosphere is moving. And those boxes have to be quite big, because of the size of our computers. Typically, they tend to be in the order of 100 kilometres by 100 kilometres. And that’s way bigger than a thunderstorm.”
The models produced for the Intergovernmental Panel on Climate Change are an important resource for climate scientists. Dr Singh hopes his investigations into “the ingredients for thunderstorms” will help make the predictions of these models more certain.
An important ingredient is “convective available potential energy”. This measures “how much energy is available in the atmosphere right now”.
“It’s a kind of hypothetical. If you took a bubble of air and you lifted it up to the upper atmosphere, how fast would it be moving by the time it got there?”
Local environmental conditions also influence the outcome.
Dr Singh’s ARC research involves constructing simulations to understand the mechanisms behind intense tropical thunderstorms. He'll test his research against what's happening in the climate now, “because we can’t observe the future climate”.
He's studying the tropics because “more people live there, and they tend to be less wealthy, so they are less able to adapt. And it's where we know a lot less about the atmosphere. And that’s because in the tropics, not only are thunderstorms numerous, but they have an important influence on the climate.”
In sub-Saharan Africa, monsoon failure leads to famine. Although many researchers have tried to understand how climate change will affect the region, their results are contradictory.
“Depending on what model you choose, drought is going to be the norm or actually it's going to get wetter – and we don’t know which it is,” Dr Singh says.
Thunderstorms are also double-edged. They can bring welcome rain, but if a storm “comes at the wrong time, they can ruin your yield for the year”.
In some regions lightning sparks bushfires, which contribute to global warming, but lightning also contributes to plant growth.
“Lightning is so energetic, it can break up nitrogen molecules in the atmosphere and create nitrogen oxides,” Dr Singh explains.
These nitrogen oxides eventually find their way into the soil, where they can be used by plants.
“Plants need nitrogen to create their proteins, and they can’t get that out of the air, because the nitrogen there has a very strong bond, but they can get it out of nitrogen oxides in the soil.”
The most deadly thunderstorms typically happen in impoverished countries where people can be highly vulnerable to natural disasters. Bangladesh, in particular, is known to have suffered through some of the most deadly storms in history.
“You get huge hailstorms, there's a lot of livestock that don’t have shelter, and even people who don’t have shelter,” Dr Singh says. “And they can’t withstand that – so you get a lot of deaths and a lot of livestock deaths.”
In Australia, thunderstorms have been responsible for massive insurance claims – Dr Singh cites a storm that dumped 500,000 tonnes of hail in Sydney in 1999, pummelling cars and houses and setting an insurance record ($2.3 billion).
Are thunderstorms getting worse?
“They haven’t been very well observed in the past,” he says, “so it's very difficult to work out if there is a real increase in trend. If you think about insurance losses, the biggest trends are caused by society becoming more affluent, so there’s more things to damage. Insurance losses certainly have gone up, but we can’t necessarily attribute that to a change in the thunderstorms themselves.”
Thunderstorms don't frighten Dr Singh. Whenever he sees one on the horizon, “I like to sit on the porch and watch it come in”, he says.
“I do enjoy them. They're very beautiful things, I think.”