The Best Australian Science Writing 2014 (12 page)

Today's forecast is the same as it's been for days: showers and a gusty storm. Locals tell me this 2012–13 wet season has been disappointingly dry, and showers and gusty storms have been in
short supply. One probable reason is the tropical cyclones to the west and east that have been sucking atmospheric energy and moisture away from the Top End.

First, Western Australia had Mitchell, Narelle and Peta. Now, in late January 2013, ex-Tropical Cyclone Oswald is rampaging through Queensland, having taken an unusual southward turn while crossing Cape York. It has spawned record-breaking rain, unprecedented flooding and half-a-dozen tornadoes.

These are just some ingredients in what the Climate Commission would later dub ‘The Angry Summer'. The BOM confirms this January has been Australia's hottest, with a national mean maximum temperature of 36.9° Celsius. The heatwave early in the month was the longest on record, with 14 of the nation's 112 high-quality climate stations experiencing their hottest day ever, the most in a single summer. A national average record was also set for the number of consecutive heatwave days – seven at more than 39° Celsius.

So while other Australians shelter or swelter, Darwinites bemoan the lack of a good storm. Still, O'Neill is upbeat. It doesn't look good today for the city, he says, but around Adelaide River, some 100 kilometres to the south, things may get interesting. The laptop reveals no storms there. And right here the sky looks awfully blue to me. I ask him why he's picked that spot. ‘I probably have a good knack for finding storms,' he says. ‘Knack is a combination of gut feeling and knowledge. Field knowledge over the years has taught me a lot. It's not a case of just looking at the radar and jumping in the car. A lot of work goes into what I do.'

That work includes studying a bunch of local, national and international forecasts online that are built on a whole slew of criteria. ‘In my head I overlay the satellite image, the radar and all the charts to make one picture. From that, and from what's happening now, I calculate what will be happening in four hours' time and decide where to go.'

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Web-based weather information is key to Mike O'Neill's lightning research. Twenty years ago,
Australian Geographic
(for whom I'm chasing storms as part of an assignment) published a major feature on the BOM's work. The fact that the bureau didn't have a website then is testament to how far its services have evolved in two decades. But there's another story here. An equally radical shift in our climate and weather has shadowed changes at the bureau. The two stories are inseparably intertwined.

Most scientists have no doubt that our planet is warming and its climate is changing as a result. They believe most of the warming derives from human activity, mainly the burning of fossil fuels. And the gases given off by this enhance the greenhouse effect – the atmosphere's ability to trap heat. Temperatures across Australia and in the surrounding oceans have risen by 1° Celsius since 1910. Most of the rise has been since the 1950s during the post-World War II global oil boom.

‘The enormous excess heat energy accumulating as a result of the greenhouse effect is intensifying the global climate and weather system,' the bureau said in its submission to the 2013 Senate Inquiry into the country's preparedness for extreme weather events. Furthermore, ‘long-term observations show that some extreme weather events are now more common and severe than in the recent past'.

Neil Plummer, the bureau's assistant director of climate information services, says the climate is evolving before our eyes. ‘Things are changing quicker now than we have seen any time before in the historical record.'

In brief, heatwaves in Australia are now longer and hotter than previously recorded and rainfall is more intense in places. Extreme heat stokes bushfires, heavier rain brings more flooding and, if it falls as hail, more damage. The evidence of this is plain
to see: the 1999 Sydney hailstorm was Australia's costliest, at $4.3 billion; the 2009 Black Saturday bushfires in Victoria struck towards the end of the ‘millennium drought' of 1997–2009, which was the worst since settlement; the Queensland floods of 2010– 11 came during one of the strongest La Niña events on record; and the remains of Cyclone Oswald drenched Queensland and northern New South Wales in 2013 – at around the same time that heatwave-boosted bushfires raged in Victoria, New South Wales and Tasmania. Ex-Tropical Cyclone Oswald's rain broke numerous records: Gladstone, in Queensland, received 820 millimetres in four days – more than the town's record for a whole month.

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An increasingly sophisticated line-up of science, technology and talent at the BOM has been monitoring, analysing, predicting and publicising the changing climate and the accompanying dramatic weather events. Underpinning all of these functions – and lying at the heart of all meteorological work – are observations.

This applies particularly to forecasting. To predict future weather, you need to know what it's doing now. The more detailed the observations, the more precise the forecast. ‘We observe the ground surface, the atmosphere, the state of the ocean and the atmosphere above the ocean,' says Sue Barrell, the bureau's assistant director of observations. ‘At ground level it's things like the temperature on the ground, soil moisture and the characteristics below the ground. It's the profile of temperature up through the atmosphere, right up to the stratosphere. It's the particles in the ozone, the composition of the atmosphere, things like CO
₂
and ozone.'

Observations don't stop at the stratosphere; they go on out into space, providing information about the Earth's magnetic
field, solar activity and solar radiation. To amass this data, the bureau deploys a formidable array of hardware. This includes high-tech Doppler radar as well as conventional radar; automatic and staffed weather stations; radiosonde balloons; marine buoys; and solar and terrestrial radiation monitoring observatories. There are also volunteer weather-watching ships, automatic weather sensors on commercial aircraft and robotic under-water gliders.

Above all, there are satellites. The US, Japan, Korea and China are some of the countries operating geostationary and polar-orbiting satellites, and the data are shared internationally. ‘Our bread-and-butter satellites in Australia are the Japanese geostationary satellites,' says Barrell. ‘From them we get imagery hourly or half-hourly that covers the whole hemisphere.'

Observations of current weather give what meteorologists call the initial conditions. From the initial conditions, a computer-based model – mathematical equations that simulate the behaviour of the atmosphere – calculates future conditions. A humungous computer does the number crunching.

For the purpose of modelling, the globe's surface and the atmosphere above it are divided into a three-dimensional grid or mesh. The numerical model checks all the weather elements at each point on this grid – some 20 million of them. From the initial conditions, it creates a forecast for a short time ahead. This then becomes the new initial state for another short forecast. The process is repeated over and over to the limit of the required forecast.

‘You move in what are called time steps,' says Kamal Puri, leader of the bureau's Earth system modelling research program. ‘Typically, depending on how fine your mesh is, these time steps can be about 10 minutes long. So you keep moving forward 10 minutes, then 10 minutes again, and 10 more minutes, until you get to 10 days ahead.'

This process would give perfect predictions but for one hitch: the initial conditions can never be exact; they always contain uncertainties and flaws. With each time step, these become magnified.

‘The errors in the initial conditions can grow very rapidly, and after about 10 days or two weeks you lose most of the predictability,' Puri says. ‘So the shorter the range of the forecast, the more accurate it is, but this short range is now moving further and further out. In the old days it was just one day. Now you're pushing to four or five days and beyond because of all the improvements.'

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‘Three big things have happened in the past 20 years that have affected what we are capable of doing now and how good we are,' says Rob Vertessy, director of meteorology. ‘First is the proliferation of data, chiefly from satellites. The satellite era has flourished and we get a phenomenal amount of data at very high resolution now. It has been a fundamental game changer. It's been aided by the internet: big, fat pipes of data coming in from all over the world.' Thirty-three geostationary and polar-orbiting satellites – 23 more than in 1993 – feed a stream of images to a dozen ground stations around Australia and its Antarctic bases. Not only are there more satellites today, they're also better. But what has really changed profoundly is the bureau's ability to exploit the data they provide.

Looking at the bureau's website, you might think that all satellites provide are pictures of land, sea and clouds. But there's more to it than that. From satellite images, meteorologists now extract information on solar radiation, sea surface temperature, vegetation, volcanic ash, temperature, water vapour and wind.

‘A lot of science is required to extract that material,' says Sue
Barrell. ‘We put a lot of effort into developing the algorithms and enhancing the products that come from the satellite data.'

Radar is also contributing to the data stream. Since 1992 the bureau has boosted its radar numbers from 38 to 66. A dozen are Doppler machines that not only show precipitation intensity, but also wind flow at different heights. This allows forecasters to see the structure of individual thunderstorms and gauge their ferocity. The second big leap has been in modelling and computing. The bigger data flow could not be processed without better models and more computing muscle. Once these were in place, forecasting accuracy shot up.

‘Twenty years ago we were doing forecasts probably out to three or four days, if we were lucky,' says Alasdair Hainsworth, assistant director of weather services. ‘Now we're doing it out to seven days. The statistics show that the seven-day forecasts are about as accurate as the four-day forecasts were 20 years ago.'

With greater skill has come fine detail or, to use the technical term, greater resolution. This means being able to tailor forecasts for ever-smaller areas. Kamal Puri explains it in terms of the mesh size of the global grid.

‘Ten years ago we would have had a mesh size typically of 100–200 kilometres,' he says. ‘Now we are getting close to a global model running at about 10–15 kilometres. That is a dramatic improvement.'

The third big leap has been in understanding the physics of the Earth's climate system. Twenty years of climate research has found its way into forecasting models, which now more faithfully reflect the system's complexity. This has refined not only short-term forecasts but also longer-term services such as the bureau's three-month seasonal outlook.

For its short-term (seven-day) forecasts, the bureau uses a series of models collectively called the Australian Community Climate and Earth-System Simulator (ACCESS), which Puri
helped develop. ACCESS is what's known as a coupled model, since it takes into consideration both atmospheric and ocean conditions. After it began operating in 2010, the error rate in short-term forecasts dropped sharply.

For long-term seasonal forecasts, the bureau uses another coupled model, the Predictive Ocean Atmosphere Model for Australia (POAMA). The first version of this model went live in 2002, producing routine forecasts of El Niño conditions, and is now being used routinely as part of the bureau's service.

The BOM's burgeoning skill set has sparked an explosion of services, many unthinkable 20 years ago. The statistics are mind-boggling. Every year the bureau delivers more than 330 000 weather forecasts, 36 000 tidal predictions and 350 000 aviation forecasts and warnings.

Its website, which went live in 1996, is its biggest outlet for this information. As well as myriad services for general users – forecasts, warnings, charts, satellite and radar images – it offers specialist programs for farmers, the defence forces, aviation, shipping, mariners, miners, water managers and commercial meteorological agencies. You can get information (with warnings, where relevant) on climate, tides, wave height, tsunamis, river flows, cyclones, bushfires, coral bleaching, space weather and volcanic ash. Some of this material comes packaged in two relatively new programs, one providing water data (on rivers, storages and aquifers) and the other environmental data.

The site gets more than 33 billion hits a year, with numbers spiking during tropical cyclones and floods. It's Australia's top site for weather information. And it continues to evolve. Currently the bureau is rolling out NexGen, its revamped modelling system.

‘NexGen encompasses a new forecasting system, new visualisations, a complete makeover of the forecasting services on our website to make it more user-friendly, adding the ability to point
and click anywhere on the map and generate a forecast,' says project manager Howard Jacobs, an exuberant tech whiz with an infectious zeal for what he does. Through its Forecast Explorer graphical viewer tool, NextGen will eventually offer seven-day forecasts for some 650 locations nationwide. And it will zoom in on 6 × 6 kilometre areas, giving severe-weather warnings where necessary.

It doesn't stop there: just over the horizon are yet more amazing gizmos. Jacobs worked on one of them, named MetEye, in 2012–13, and an ‘experimental' version of its service has now gone live. He calls it Google Maps for weather. It will replace Forecast Explorer and allow users to customise their weather maps, combining features such as forecasts, radar images, cloud, temperature, rainfall figures, wind, waves and tides for their chosen location.

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All the skills the BOM can now mobilise to peer into the distant future are revealing an unsettling scenario, one where climbing temperatures continue to cook our weather and climate into an increasingly volatile stew.