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.

How TV weather presenters can improve public understanding of climate change



File 20170925 21172 q4lddb

shutterstock

David Holmes, Monash University

A recent Monash University study of TV weather presenters has found a strong interest from free-to-air presenters in including climate change information in their bulletins.

The strongest trends in the survey, which had a 46% response rate, included:

  • 97% of respondents thought climate change is happening;

  • 97% of respondents believed viewers had either “strong trust” or “moderate trust” in them as a reliable source of weather information;

  • 91% of respondents were comfortable with presenting local historical climate statistics, and just under 70% were comfortable with future local climate projections; and

  • 97% of respondents thought their audiences would be interested in learning about the impacts of climate change.

According to several analyses of where Australians get their news, in the age of ubiquitous social media TV is still the single largest news source.

And when one considers that social media and now apps are increasingly used as the interface for sharing professional content from news organisations – which includes TV news – the reach of TV content is not about to be challenged anytime soon.

The combined audience for primetime free-to-air TV in the five capital city markets alone is a weekly average of nearly 3 million viewers. This does not include those using catch-up on portable devices, and those watching the same news within the pay TV audience. And there are those who are getting many of the same news highlights and clips through their Facebook feeds and app-based push media.

Yet the ever-more oligopolistic TV industry in Australia is very small. And professional weather presenters are a rather exclusive group: there are only 75 such presenters in Australia.

It is because of this, rather than in spite of it, that weather presenters are able to command quite a large following. And they are highly promoted by the networks themselves – on freeway billboards and station advertising. This promotion makes weather presenters among the most trusted media personalities, while simultaneously presenting information that is regarded as apolitical.

At the same time, Australians have a keen interest in talking about weather. It tends to unite us.

These three factors – trust, the impartial nature of weather, and Australian’s enthusiasm for the weather – puts TV presenters in an ideal position to present climate information. Such has been the experience in the US, where the Centre for Climate Change Communication together with Climate Matters have partnered with more than 350 TV weathercasters to present simple, easy-to-process factual climate information.

In the US it is about mainstreaming climate information as factual content delivered by trusted sources. The Climate Matters program found TV audiences value climate information the more locally based it was.

Monash’s Climate Change Communication Research Hub is conducting research as a precondition to establishing such a program in Australia. The next step is to survey the audiences of the free-to-air TV markets in the capital city markets to evaluate Australians’ appetite for creating a short climate segment alongside the weather on at least a weekly basis.

As in the US, TV audiences are noticing more and more extreme weather and want to understand what is causing it, and what to expect in the future.

The Climate Change Communication Research Hub is also involved in creating “climate communications packages” that can be tested with audiences. These are largely based on calendar and anniversary dates, and show long-term trends using these dates as datapoints.

The calendar dates could be sporting dates, or how climate can be understood in relation to a collection of years based on a specific date, or the start of a season for fire or cyclones. There has been so much extreme weather in recent years that there are plenty of anniversaries.

Let’s take November 21, 2016 – the most severe thunderstorm asthma event ever to impact Melbourne. It saw 8,500 presentations to hospital emergency departments and nine tragic deaths.

There is no reason why this event can’t be covered this year in the context of climate as a community service message. As explained in the US program, just a small increase in higher average spring temperatures leads to the production of a higher count of more potent pollen. Also, as more energy is fed into the destructive power of storm systems, the prospect of breaking up pollen and distributing it efficiently throughout population centres is heightened.

The need to be better prepared for thunderstorms in spring is thus greater, even for those who have never had asthma before.

For its data, the Climate Change Communication Research Hub will be relying on the information from the Bureau of Meteorology and the CSIRO, but will call on the assistance of a wide range of organisations such as the SES, state fire services, and health authorities in conducting its research.

In February 2018, the hub will hold a workshop with TV weather presenters as part of the Australian Meteorological and Oceanographic Society conference. At the conference the planning for the project will be introduced, with a pilot to be conducted on one media market to be rolled out to multiple markets in the second year.

The ConversationThe program is not intended to raise the level of concern about climate change, but public understanding of it. As survey after survey shows, Australians are already concerned about climate change. But more information is needed about local and regional impacts that will help people make informed choices about mitigation, adaptation and how to plan their lives – beyond tomorrow’s weather.

David Holmes, Director, Climate Change Communication Research Hub, Monash University

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