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.

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Extreme weather leads to public health crises – so health and climate experts must work together


Aparna Lal, Australian National University and Rebecca Colvin, Australian National University

This year has seen a number of extreme weather events around the globe, from hurricanes in the Americas to devastating flooding in South Asia. The loss of lives, homes and livelihoods are made worse by subsequent disease outbreaks: after the South Asian floods, more than 12,000 cases of watery diarrhoea were reported in Bangladesh. Presumably, many more cases are unreported.

As our climate changes, severe weather events (especially intense rainfall) will become the “new normal”. The connection between climate and disease is well established, even in less extreme situations.


Read more: Irma and Harvey: very different storms, but both affected by climate change


This makes it vital that our meteorologists, climate scientists and health systems work closely together. Particularly, health professionals should make better use of weather forecasts to proactively manage disease risk. Climate outlooks – with a longer-term perspective than weather forecasts – can also help with long-range tactical and strategic planning.

The link between climate change and disease

Climate change projections consistently indicate increased climate variability. A more variable climate creates conditions for the spread and control of infectious disease. In particular, changes in the intensity and duration of rain can help spread pathogens through water.

Both floods and droughts can increase waterborne infections, either when clean and dirty water mix during floods, or through inadequate storage and concentration of toxic organisms when water is scarce.


Read more: Flooding from Hurricane Harvey causes a host of public health concerns


These risks are not restricted to countries with limited resources. In Australia, fluctuations in the sea surface temperatures in the Indian Ocean (a phenomenon shown by the “Indian Ocean Dipole”) are linked to spikes in rates of waterborne diseases like cryptosporidiosis, which cause gastrointestinal illness.

NSW Health documents, obtained earlier this year by the ABC, reveal that more than 100,000 NSW residents were issued protective boil-water alerts in the past five years. These residents lived in areas where pathogens like cryptosporidium were found in unfiltered drinking water pumped from rivers, lakes and dams. A more variable climate can increase these risks.

Research suggests we can improve public health outcomes by integrating both climate dynamics and the impact on human health into our management of natural water resources.

We need integrated climate and health systems

Traditional disease surveillance systems rely on early detection of illnesses as they occur, not predicting them before they happen. But outbreaks that follow extreme events are already underway before authorities are notified.

The close relationship between climate signals and some waterborne diseases suggest that advances in numerical weather forecasting and climate science present new opportunities for public health officials.


Read more: How satellites can help control the spread of diseases such as Zika


Forecasting based on climate variables is well established in crop disease management and ecosystem conservation.

Recent technological advancements, such as real-time predictions of disease outbreaks, highlight great potential for forecasting to be used for human health benefit ahead of extreme weather events.

Collaboration is key

At present, health professionals and climate forecasters generally operate separately from each other, as very distinct professions. This can make it very difficult for researchers, public servants and service providers to work effectively together.

Our experience at the ANU Climate Change Institute has taught us that an important early step to fostering cooperation is helping individuals build relationships.


Read more: We’ve got to stop meeting like this


It’s important to create opportunities for people from different sectors to come together so they can exchange knowledge and make personal connections. Emphasising that health and climate experts have many shared goals can help encourage new cross-sector networks and a sense of a shared professional identity. (And realistically, one of the most important things you can do to promote productive exchanges is feed people well.)

There’s a real opportunity to integrate health and climate knowledge bases. This could be what’s known as a “boundary object”: something that can be meaningfully interpreted by people with different training and backgrounds, which helps to span the “boundary” between these sectors or disciplines.

We stand to gain from integration across climate and health

As our understanding of climate patterns grows, there are more opportunities for the health sector to take advantage of sophisticated modelling and prediction.

This is particularly true if disease surveillance and climate and weather forecasting can be combined to assess health risks ahead of extreme weather events, rather than during or after the fact.

The ConversationBy fostering collaboration and the integration of the health and climate sectors, we can improve our capacity to respond to the health risks posed by climate change.

Aparna Lal, Research Fellow, Australian National University and Rebecca Colvin, Knowledge Exchange Specialist, Australian National University

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

Why hot weather records continue to tumble worldwide


Andrew King, University of Melbourne

It sometimes feels like we get a lot of “record-breaking” weather. Whether it’s a heatwave in Europe or the “Angry Summer” in Australia, the past few years have seen temperature records tumble.

This is the case both locally – Sydney had its hottest year on record in 2016 – and globally, with the world’s hottest year in 2016 beating the record set only the year before.

Some of 2016’s heat was due to the strong El Niño. But much of it can be linked to climate change too.

We’re seeing more heat records and fewer cold records. In Australia there have been 12 times as many hot records as cold ones in the first 15 years of this century.

If we were living in a world without climate change, we would expect temperature records to be broken less often as the observational record grows longer. After all, if you only have five previous observations for annual temperatures then a record year isn’t too surprising, but after 100 years a new record is more notable.

In contrast, what we are seeing in the real world is more hot temperature records over time, rather than less. So if you think we’re seeing more record-breaking weather than we should, you’re right.

Why it’s happening

In my new open-access study published in the journal Earth’s Future, I outline a method for evaluating changes in the rate at which temperature records are being broken. I also use it to quantify the role of the human influence in this change.

To do it, I used climate models that represent the past and current climate with both human influences (greenhouse gas and aerosol emissions) and natural influences (solar and volcanic effects). I then compared these with models containing natural influences only.

Lots of hot records, fewer cold ones

Taking the example of global annual temperature records, we see far more record hot years in the models that include the human influences on the climate than in the ones without.

Crucially, only the models that include human influences can recreate the pattern of hot temperature records that were observed in reality over the past century or so.

Observed and model-simulated numbers of hot and cold global annual temperature records for 1861-2005. Observed numbers of record occurrences are shown as black circles with the model-simulated record numbers under human and natural influences (red box and whiskers) and natural influences only (orange box and whiskers) also shown. The central lines in the boxes represent the median; the boxes represent interquartile range.
Author provided

In contrast, when we look at cold records we don’t see the same difference. This is mainly because cold records were more likely to be broken early in the temperature series when there were fewer previous data. The earliest weather data comes from the late 19th century, when there was only a weak human effect on the climate relative to today. This means that there is less difference between my two groups of models.

In the models that include human influences on the climate, we see an increase in the number of global record hot years from the late 20th century onwards, whereas this increase isn’t seen in the model simulations without human influences. Major volcanic eruptions reduce the likelihood of record hot years globally in both groups of model simulations.

Projecting forward to 2100 under continued high greenhouse gas emissions, we see the chance of new global records continuing to rise, so that one in every two years, on average, would be a record-breaker.

Chance of record hot global annual temperatures in climate models with human and natural influences (red) and natural influences only (orange). Grey curve shows the statistical likelihood of a new hot record each year (100% in the first year, 50% in the second year, 33% in the third year, and so on). Grey vertical bars show the timing of major volcanic eruptions through the late-19th and 20th centuries.
Author provided

I also looked at specific events and how much climate change has increased the likelihood of a record being broken.

I used the examples of the record hot years of 2016 globally and 2014 in Central England. Both records were preceded by well over a century of temperature observations, so in a non-changing climate we would expect the chance of a record-breaking year to be less than 1%.

Instead, I found that the chance of setting a new record was increased by at least a factor of 30 relative to a stationary climate, for each of these records. This increased likelihood of record-breaking can be attributed to the human influence on the climate.

More records to come?

The fact that we’re setting so many new hot records, despite our lengthening observation record, is an indicator of climate change and it should be a concern to all of us.

The ConversationThe increased rate at which we are getting record hot temperatures is controlled by the speed of global warming, among other factors. To meet the Paris target of keeping global warming below 2℃ we will have to reduce our greenhouse gas emissions drastically. Besides keeping average global temperatures under control, this would also reduce the chance of temperature records continuing to tumble, both globally and locally.

Andrew King, Climate Extremes Research Fellow, University of Melbourne

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

Tropical thunderstorms are set to grow stronger as the world warms



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A supercell thunderstorm in the US state of Oklahoma.
Hamish Ramsay, Author provided

Martin Singh, Monash University

Thunderstorms are set to become more intense throughout the tropics and subtropics this century as a result of climate change, according to new research.

Thunderstorms are among nature’s most spectacular phenomena, producing lightning, heavy rainfall, and sometimes awe-inspiring cloud formations. But they also have a range of important impacts on humans and ecosystems.

For instance, lightning produced by thunderstorms is an important trigger for bushfires globally, while the hailstorm that hit Sydney in April 1999 remains Australia’s costliest ever natural disaster.


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


Given the damage caused by thunderstorms in Australia and around the world, it is important to ask whether they will grow in frequency and intensity as the planet warms.

Our main tools for answering such questions are global climate models – mathematical descriptions of the Earth system that attempt to account for the important physical processes governing the climate. But global climate models are not fine-scaled enough to simulate individual thunderstorms, which are typically only a few kilometres across.

But the models can tell us about the ingredients that increase or decrease the power of thunderstorms.

Brewing up a storm

Thunderstorms represent the dramatic release of energy stored in the atmosphere. One measure of this stored energy is called “convective available potential energy”, or CAPE. The higher the CAPE, the more energy is available to power updrafts in clouds. Fast updrafts move ice particles in the cold, upper regions of a thunderstorm rapidly upward and downward through the storm. This helps to separate negatively and positively charged particles in the cloud and eventually leads to lightning strikes.

To create thunderstorms that cause damaging wind or hail, often referred to as severe thunderstorms, a second factor is also required. This is called “vertical wind shear”, and it is a measure of the changes in wind speed and direction as you rise through the atmosphere. Vertical wind shear helps to organise thunderstorms so that their updrafts and downdrafts become physically separated. This prevents the downdraft from cutting off the energy source of the thunderstorm, allowing the storm to persist for longer.

By estimating the effect of climate change on these environmental properties, we can estimate the likely effects of climate change on severe thunderstorms.

Stormy forecast

My research, carried out with US colleagues and published today in Proceedings of the National Academy of Sciences, does just that. We examined changes in the energy available to thunderstorms across the tropics and subtropics in 12 global climate models under a “business as usual” scenario for greenhouse gas emissions.

In every model, days with high values of CAPE grew more frequent, and CAPE values rose in response to global warming. This was the case for almost every region of the tropics and subtropics.

These simulations predict that this century will bring a marked increase in the frequency of conditions that favour severe thunderstorms, unless greenhouse emissions can be significantly reduced.

Change in frequency (in days per year) of favourable conditions for severe thunderstorms for 2081-2100, compared with 1981-2000 averaged across 12 climate models under the RCP8.5 greenhouse-gas concentration scenario. Stippling indicates regions where 11 of the 12 models agree on the sign of the change.
CREDIT, Author provided

Previous studies have made similar predictions for severe thunderstorms in eastern Australia and the United States. But ours is the first to study the tropics and subtropics as a whole, a region that is characterised by some of the most powerful thunderstorms on Earth.

What drives the increased energy?

Different climate models, constructed by different research groups around the world, all agree that global warming will increase the energy available to thunderstorms – a prediction underlined by our new research. But we need to understand why this happens, so as to be sure that the effect is real and not a product of faulty model assumptions.

My colleagues and I previously proposed that high levels of CAPE can develop in the tropics as a result of the turbulent mixing that occurs when clouds draw in air from their surroundings. This mixing prevents the atmosphere from dissipating the available energy too quickly. Instead, the energy builds up for longer and is released in less frequent but more intense storms.

As the climate warms, the amount of water vapour required for cloud formation increases. This is the result of a well-known thermodynamic relationship called the Clausius-Clapeyron relation. In a warmer climate this means the difference in the humidity between the clouds and their surroundings becomes larger. As a result, the mixing mechanism becomes more efficient in building up the available energy. This, we argue, accounts for the increase in CAPE seen in our model simulations.

In our new study, we tested this idea in a global climate model by artificially increasing the strength of the mixing between clouds and their surroundings. As expected, this change produced a large increase in the energy available to thunderstorms in our model.


Read more: Australia faces a stormier future thanks to climate change


Another prediction of our hypothesis is that days with both high values of CAPE and heavy precipitation tend to occur when the atmosphere is least humid in its middle levels (at altitudes of a few kilometres). Using real data from weather balloons, we confirmed that this is the case across the tropics and subtropics.

What this means for future thunderstorms

The models predict that the energy available for thunderstorms will increase as the Earth warms. But how much more intense will storms actually become as a result?

The answer to that question is currently uncertain, and answering it is the next job for me, and other researchers around the world.

The ConversationBut it is clear that through our continued greenhouse gas emissions, we are increasing the fuel available to the strongest thunderstorms. Exactly how much stronger our future thunderstorms will ultimately become remains to be seen.

Martin Singh, Lecturer, School of Earth, Atmosphere and Environment, Monash University

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

El Niño in the Pacific has an impact on dolphins over in Western Australia



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Leaping bottlenose dolphins.
Kate Sprogis/MUCRU, Author provided

Kate Sprogis, Murdoch University; Fredrik Christiansen, Murdoch University; Lars Bejder, Murdoch University, and Moritz Wandres, University of Western Australia

Indo-Pacific bottlenose dolphins (Tursiops aduncus) are a regular sight in the waters around Australia, including the Bunbury area in Western Australia where they attract tourists.

The dolphin population here, about 180km south of Perth, has been studied quite intensively since 2007 by the Murdoch University Cetacean Unit. We know the dolphins here have seasonal patterns of abundance, with highs in summer/autumn (the breeding season) and lows in winter/spring.

But in winter 2009, the dolphin population fell by more than half.

A leaping bottlenose dolphin.
Kate Sprogis/MUCRU, Author provided

This decrease in numbers in WA could be linked to an El Niño event that originated far away in the Pacific Ocean, we suggest in a paper published today in Global Change Biology. The findings could have implications for future sudden drops in dolphin numbers here and elsewhere.


Read more: Tackling the kraken: unique dolphin strategy delivers dangerous octopus for dinner


A Pacific event

The El Niño Southern Oscillation (ENSO) results from an interaction between the atmosphere and the tropical Pacific Ocean. ENSO periodically fluctuates between three phases: La Niña, Neutral and El Niño.

During our study from 2007 to 2013, there were three La Niña events. There was one El Niño event in 2009, with the initial phase in winter being the strongest across Australia.

The blue vertical line shows the decline in dolphin numbers (d) during the 2009 El Niño event.
Kate Sprogis, Author provided

Coupled with El Niño, there was a weakening of the Leeuwin Current, the dominant ocean current off WA. There was also a decrease in sea surface temperature and above average rainfall.

ENSO is known to affect the strength of the south-ward flowing Leeuwin Current.

During La Niña, easterly trade winds pile warm water on the western side of the Pacific Ocean. This westerly flow of warm water across the top of Australia through the Indonesian Throughflow results in a stronger Leeuwin Current.

During El Niño, trade winds weaken or reverse and the pool of warm water in the Pacific Ocean gathers on the eastern side of the Pacific Ocean. This results in a weaker Indonesian Throughflow across the top of Australia and a weakening in strength of the Leeuwin Current.

A chart showing sea surface temperature (SST) anomalies off Western Australia. Note the extremes for the moderate El Niño in 2009 (blue rectangle), and the strong La Niña in 2011 (red rectangle)
Moritz Wandres, Author provided

The strength and variability of the Leeuwin Current coupled with ENSO affects species biology and ecology in WA waters. This includes the distribution of fish species, the transport of rock lobster larvae, the seasonal migration of whale sharks and even seabird breeding success.

The question we asked then was whether ENSO could affect dolphin abundance?

What happened during the El Niño?

These El Niño associated conditions may have affected the distribution of dolphin prey, resulting in the movement of dolphins out of the study area in search of adequate prey elsewhere.

A surfacing bottlenose dolphin.
Kate Sprogis/MUCRU, Author provided

This is similar to what happens for seabirds in WA. During an El Niño event with a weakened Leeuwin Current, the distribution of prey changes around seabird’s breeding colonies resulting in a lower abundance of important prey species, such as salmon.

This in turn negatively impacts seabirds, including a decrease in reproductive output and changes in foraging.

In southwestern Australia, the amount of rainfall is strongly connected to sea surface temperature. When the water temperature in the Indian Ocean decreases, the region receives higher rainfall during winter.

High levels of rainfall contribute to terrestrial runoff and alters freshwater inputs into rivers and estuaries. The changes in salinity influences the distribution and abundance of dolphin prey.

This is particularly the case for the river, estuary, inlet and bay around Bunbury. Rapid changes in salinity during the onset of El Niño may have affected the abundance and distribution of fish species.

In 2009, there was also a peak in strandings of dead bottlenose dolphins in WA (between 1981-2010), but the cause of this remains unknown.

Of these strandings, in southwest Australia, there was a peak in June that coincided with the onset of the 2009 El Niño.

Specifically, in the Swan River, Perth, there were several dolphin deaths, with some resident dolphins that developed fatal skin lesions that were enhanced by the low-salinity waters.

What does all this mean?

Our study is the first to describe the effects of climate variability on a coastal, resident dolphin population.

A group of bottlenose dolphins.
Kate Sprogis/MUCRU, Author provided

We suggest that the decline in dolphin abundance during the El Niño event was temporary. The dolphins may have moved out of the study area due to changes in prey availability and/or potentially unfavourable water quality conditions in certain areas (such as the river and estuary).


Read more: Explainer: El Niño and La Niña


Long-term, time-series datasets are required to detect these biological responses to anomalous climate conditions. But few long-term datasets with data collected year-round for cetaceans (whales, dolphins and porpoises) are available because of logistical difficulties and financial costs.

Continued long-term monitoring of dolphin populations is important as climate models provide evidence for the doubling in frequency of extreme El Niño events (from one event every 20 years to one event every ten years) due to global warming.

The ConversationWith a projected global increase in frequency and intensity of extreme weather events (such as floods, cyclones), coastal dolphins may not only have to contend with increasing coastal human-related activities (vessel disturbance, entanglement in fishing gear, and coastal development), but also have to adapt to large-scale climatic changes.

Kate Sprogis, Research associate, Murdoch University; Fredrik Christiansen, Postdoctoral Research Fellow, Murdoch University; Lars Bejder, Professor, Cetacean Research Unit, Murdoch University, Murdoch University, and Moritz Wandres, Oceanographer PhD Student, University of Western Australia

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