How weather radar can keep tabs on the elusive magpie goose


Magpie Geese taking off from a mango orchard in the Northern Territory.
Rebecca Rogers, Author provided

Rebecca Rogers, Charles Darwin University

You’re probably familiar with weather radar that shows bands of rain blowing in to ruin your plans for the day, or the ominous swirling pattern of a cyclone.

But rain isn’t the only thing that shows up on the radar screen. Anything moving through the sky will – like a large group of birds in flight.

Ecologists have begun to realise that weather radar data have huge potential to reveal the movements of flying animals all over the country.

At the forefront of this research is the magpie goose, an occasionally controversial waterbird prized by some and detested by others.

It’s a lovely day in northern Australia, and you are a magpie goose. These waterbirds are an ideal test case for weather-radar tracking.
Shutterstock

Chasing angels

To understand how we got to this point, first we need to go back 80 years. Prior to World War II, engineers were racing to improve radar systems to detect enemy aircraft when they noticed strange unexplained rings on their screens that they called angels.

Some of these angels, they realised later, were caused by groups of birds and bats taking off and flying through the radar beam. Since this discovery, there has been a steady increase in researchers using weather radar to understand how and why animals move through the air.

How weather radar works

Radar works by sending out a sweeping beam of radio waves and listening for echoes. It processes these echoes to map the positions of objects around it.

With weather radar, the radar beam won’t only bounce off raindrops – it will also reflect back from birds. Some weather radars send out these pulses at a precise frequency, which allows them to use the Doppler effect to determine how fast objects are moving towards or away from the radar.

Meteorologists have ways to filter out clutter caused by flying animals, so they can see where it is raining. Ecologists are doing the reverse, filtering out rain from the raw data collected by weather radars in order to track the movements of birds, bats and even insect swarms.

Weather radars cover a good part of the Australian continent, which makes them very useful for tracking birds.
Rogers et al. (2019) – Austral Ecology

Most weather radars can give us a three-dimensional picture of what is happening in the air every 5–10 minutes. In Australia the data is archived for years and even decades in some places, and it is all available free of charge for researchers. This means we can not only understand how animals are using the airspace now, but also how these movement patterns may have changed over time.

Is it a bird? Is it a plane?

So how do we actually tell whether those pixels on the screen are caused by rain, birds or something less common like bushfire smoke?

This is where things can get a bit more tricky. For some cases, like tracking bats coming out of a cave or roost tree, the job for the ecologist is fairly simple. For roosting species like these, we often observed very characteristic rings on the radar similar to the angels described by those early radar engineers. Examples of the rings can be found all over Australia caused by flying foxes.

Flying animals leave traces in weather radar images. The image at left shows an ‘angel echo’ caused by flying foxes coming out of a roost in NSW, while the one on the right reveals ‘blooms’ of activity on the Darwin radar, likely to be caused by magpie geese and other waterbirds taking off for their morning feeding flights.
Rogers et al. (2019) – Austral Ecology

For broadly distributed species, like the magpie geese found all across northern Australia, the picture is not so easy to interpret. These animals tend to produce patterns best described as blooms of activity: they appear across the radar image, spreading out and then blending together like a bunch of flowers blooming all at once.

These patterns can look similar to rain clouds to the untrained eye. However, with some understanding of how the radar works and the behaviour of the birds – like when they are active or how high they fly – we can quickly begin to narrow down what might be causing different patterns on radar images.

Why track magpie geese?

Magpie geese cross paths with humans in many different ways.

They are hunted by Indigenous people for food, they are considered a pest for mango farmers and a strike risk for planes, and they could be vectors for disease.

Tracking magpie geese can help us better understand this native species and ensure it thrives long into the future.




Read more:
Most native bird species are losing their homes, even the ones you see every day


Like many waterbirds, magpie geese have distinct daily patterns of movement, which makes them ideal candidates for trialling the use of weather radar to track Australian birds.

In Darwin, blooms of activity occur all over the radar in the morning and evening when magpie geese are taking off from wetlands and mango orchards for their daily feeding flights.

By using GPS tracking collars and annual survey data, we are starting to see how these patterns in the radar data correspond to real behaviour. These results are showing how weather radar could be repurposed to track the movement of magpie geese – and after that, many other kinds of birds in Australia.The Conversation

Rebecca Rogers, PhD Candidate, Charles Darwin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

All hail new weather radar technology, which can spot hailstones lurking in thunderstorms


Joshua Soderholm, The University of Queensland; Alain Protat, Australian Bureau of Meteorology; Hamish McGowan, The University of Queensland; Harald Richter, Australian Bureau of Meteorology, and Matthew Mason, The University of Queensland

An Australian spring wouldn’t be complete without thunderstorms and a visit to the Australian Bureau of Meteorology’s weather radar website. But a new type of radar technology is aiming to make weather radar even more useful, by helping to identify those storms that are packing hailstones.

Most storms just bring rain, lightning and thunder. But others can produce hazards including destructive flash flooding, winds, large hail, and even the occasional tornado. For these potentially dangerous storms, the Bureau issues severe thunderstorm warnings.

For metropolitan regions, warnings identify severe storm cells and their likely path and hazards. They provide a predictive “nowcast”, such as forecasts up to three hours before impact for suburbs that are in harm’s way.


Read more: To understand how storms batter Australia, we need a fresh deluge of data


When monitoring thunderstorms, weather radar is the primary tool for forecasters. Weather radar scans the atmosphere at multiple levels, building a 3D picture of thunderstorms, with a 2D version shown on the bureau’s website.

This is particularly important for hail, which forms several kilometres above ground in towering storms where temperatures are well below freezing.

Bureau of Meteorology 60-minute nowcast showing location and projected track of severe thunderstorms in 10-minute steps.
Australian Bureau of Meteorology

In terms of insured losses, hailstorms have caused more insured losses than any other type of severe weather events in Australia. Brisbane’s November 2014 hailstorms cost an estimated A$1.41 billion, while Sydney’s April 1999 hailstorm, at A$4.3 billion, remains the nation’s most costly natural disaster.

Breaking the ice

Nonetheless, accurately detecting and estimating hail size from weather radar remains a challenge for scientists. This challenge stems from the diversity of hail. Hailstones can be large or small, densely or sparsely distributed, mixed with rain, or any combination of the above.

Conventional radars measure the scattering of the radar beams as they pass through precipitation. However, a few large hailstones can look the same as lots of small ones, making it hard to determine hailstones’ size.

A new type of radar technology called “dual-polarisation” or “dual-pol” can solve this problem. Rather than using a single radar beam, dual-pol uses two simultaneous beams aligned horizontally and vertically. When these beams scatter off precipitation, they provide relative measures of horizontal and vertical size.

Therefore, an observer can see the difference between flatter shapes of rain droplets and the rounder shapes of hailstones. Dual-pol can also more accurately measure the size and density of rain droplets, and whether it’s a mixture or just rain.

Together, these capabilities mean that dual-pol is a game-changer for hail detection, size estimation and nowcasting.

Into the eye of the storm

Dual-pol information is now streaming from the recently upgraded operational radars in Adelaide, Melbourne, Sydney and Brisbane. It allows forecasters to detect hail earlier and with more confidence.

However, more work is needed to accurately estimate hail size using dual-pol. The ideal place for such research is undoubtedly southeast Queensland, the hail capital of the east coast.

When it comes to thunderstorm hazards, nothing is closer to reality than scientific observations from within the storm. In the past, this approach was considered too costly, risky and demanding. Instead, researchers resorted to models or historical reports.

The Atmospheric Observations Research Group at the University of Queensland (UQ) has developed a unique capacity in Australia to deploy mobile weather instrumentation for severe weather research. In partnership with the UQ Wind Research Laboratory, Guy Carpenter and staff in the Bureau of Meteorology’s Brisbane office, the Storms Hazards Testbed has been established to advance the nowcasting of hail and wind hazards.

Over the next two to three years, the testbed will take a mobile weather radar, meteorological balloons, wind measurement towers and hail size sensors into and around severe thunderstorms. Data from these instruments provide high-resolution case studies and ground-truth verification data for hazards observed by the Bureau’s dual-pol radar.

Since the start of October, we have intercepted and sampled five hailstorms. If you see a convoy of UQ vehicles heading for ominous dark clouds, head in the opposite direction and follow us on Facebook instead.

UQ mobile radar deployed for thunderstorm monitoring.
Kathryn Turner

Unfortunately, the UQ storm-chasing team can’t get to every severe thunderstorm, so we need your help! The project needs citizen scientists in southeast Queensland to report hail through #UQhail. Keep a ruler or object for scale (coins are great) handy and, when a hailstorm has safely passed, measure the largest hailstone.

Submit reports via uqhail.com, email, Facebook or Twitter. We greatly appreciate photos with a ruler or reference object and approximate location of the hail.

How to report for uqhail.

Combining measurements, hail reports and the Bureau of Meteorology’s dual-pol weather radar data, we are working towards developing algorithms that will allow hail to be forecast more accurately. This will provide greater confidence in warnings and those vital extra few minutes when cars can be moved out of harm’s way, reducing the impact of storms.


Read more: Tropical thunderstorms are set to grow stronger as the world warms


Advanced techniques developed from storm-chasing and citizen science data will be applied across the Australian dual-pol radar network in Sydney, Melbourne and Adelaide.

The ConversationWho knows, in the future if the Bureau’s weather radar shows a thunderstorm heading your way, your reports might even have helped to develop that forecast.

Joshua Soderholm, Research scientist, The University of Queensland; Alain Protat, Principal Research Scientist, Australian Bureau of Meteorology; Hamish McGowan, Professor, The University of Queensland; Harald Richter, Senior Research Scientist, Australian Bureau of Meteorology, and Matthew Mason, Lecturer in Civil Engineering, The University of Queensland

This article was originally published on The Conversation. Read the original article.