Winter is coming, and it’s looking mighty mild



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Brrr! It’s cold in here!
Alpha/Flickr, CC BY-SA

Jonathan Pollock, Australian Bureau of Meteorology and Andrew B. Watkins, Australian Bureau of Meteorology

After an exceptionally warm and dry autumn, it’s time to look ahead to see what’s in store for winter. The Bureau of Meteorology’s climate outlooks for winter, issued today, shows above-average temperatures and below-average rainfall are likely across southern Australia. While some of us will relish the prospect of a mild winter, the dry isn’t necessarily good news for everyone.




Read more:
When is it going to snow? Getting a fix on what can make a good season


Warm lead-up to winter

Summer-like conditions continued into early autumn for much of southern Australia, including an exceptional heatwave in early April. Temperatures in autumn were warmer than average across much of the continent. New South Wales, South Australia, Western Australia and Victoria all experienced one of their warmest autumns since at least 1900. Overnight temperatures have also been warmer than average in most parts.

Autumn maximum temperature map.
Bureau of Meterology

Very dry autumn for the southern mainland

For many southern areas autumn wasn’t just warm, it was also extremely dry. New South Wales, Victoria, southwest Western Australia and South Australia all had one of their driest autumns on record.

Many farmers in southern Australia look to the autumn break – the first significant rain event (25mm or more) after summer – to kick off the crop and pasture growing season. The autumn break arrived by mid-May across southern Victoria, eastern New South Wales and southwest coastal Western Australia. However, farmers in northwest Victoria, inland New South Wales, eastern South Australia and much of inland Western Australia didn’t receive an autumn break this year.

One of reasons for the warm and dry autumn in the south was higher than average pressure over southern Australia. The high pressure meant rain bearing cold fronts from the Southern Ocean couldn’t push up into southern Australia.

Autumn rainfall map.
Bureau of Meterology

No strong influence from Pacific or Indian Ocean this winter

So, will this pattern of warm and dry continue? Two of the major drivers of Australia’s climate, the El Niño–Southern Oscillation (ENSO) in the Pacific Ocean, and its equivalent in the Indian Ocean, the Indian Ocean Dipole (IOD), were neutral during autumn, and are likely to remain so throughout winter.




Read more:
Droughts and flooding rains: it takes three oceans to explain Australia’s wild 21st-century weather


Of the eight international climate models surveyed by the Bureau of Meteorology, seven predict winter will see ENSO-neutral sea surface temperatures in the central Pacific, with only one model forecasting a warming to El Niño levels by August.

Models also suggest the Indian Ocean Dipole (IOD) will remain neutral through winter. But there is quite a range of scenarios from the international modelling centres the Bureau assesses. One model is predicting a positive IOD over winter, one model predicting a negative IOD in spring, and the other four are neutral. Typically, when the ENSO and IOD are both neutral there is no strong shift in the outlook towards widespread wetter or drier conditions across most of Australia.




Read more:
Explainer: El Niño and La Niña


Most international model outlooks for the ENSO sea surface temperature index in the central Pacific Ocean (NINO3.4) remain neutral in August.
Model outlooks provided by: BoM (Bureau of Meteorology), CanSIPS (Canadian Seasonal to Interannual Prediction System), ECMWF (European Centre for Medium-Range Weather Forecasts), JMA (Japan Meteorological Agency), Météo France, NASA (National Aeronautics
Most international model outlooks for the IOD sea surface temperature index remain neutral in August.
Model outlooks provided by: BoM (Bureau of Meteorology), CanSIPS (Canadian Seasonal to Interannual Prediction System), ECMWF (European Centre for Medium-Range Weather Forecasts), Météo France, NASA (National Aeronautics and Space Administration), and the

However, when these major drivers are neutral, other factors can have a greater influence on Australian rainfall and temperature patterns. For instance, forecast warmer-than-usual temperatures in the Tasman Sea and the associated lower-than-normal air pressure this winter is likely to contribute to a weakening of westerly winds over southern Australia that would normally draw cold fronts up from the Southern Ocean.




Read more:
The BOM outlook for the weather over the next three months is ‘neutral’ – here’s what that really means


So, what’s the outlook for winter?

As a result of the weakened westerly winds, below-average winter rainfall is likely for western parts of Western Australia, and for most of New South Wales extending across the border into southern Queensland and northern Victoria. For most other parts, the outlook is neutral, meaning roughly equal chances of above- or below-average rainfall.

The outlook for June is looking particularly dry across most of the southern mainland.

The likely reduction in cold fronts, and clearer skies over much of the continent means warmer-than-average temperatures are favoured across southern Australia, with the strongest likelihood (about 80%) in the southeast.

The model suggests there is also an above-normal likelihood of winter “mildwaves” – periods of very mild weather – along Australia’s southeast coast.




Read more:
Winter heatwaves are nice … as extreme weather events go


So, what does this all mean? For farmers and those working in the agricultural sectors, the warmer temperatures mean soils will stay warm longer. This is likely to keep the crop and pasture growing window open a little longer before the cold of winter. Dry conditions are likely to mean a slow and possibly late start to the growing season, potentially pushing the crop harvest later into the warmer months of 2018, when heatwaves can become a problem.

What does this mean for the snow season?

For skiers, a later start to the season becomes more likely with a warm and dry June expected. On the other hand, neutral ENSO conditions typically bring snow cover that’s a little deeper than average by mid-season.

This is a contrast to strong El Niño or La Niña phases, which both typically mean less snow than usual, but for different reasons. El Niño phases mean less rainfall and warmer days during the snow season. La Niña years usually have more rain, but temperatures can be too high for snow to form.

This has happened more often in recent decades because of climate change. Historically, neutral years have had more consistent good snow depths than either El Niño or La Niña years, so late winter should be a good time to hit the slopes.


The ConversationFor more details on the long-range forecast for winter, visit our Climate Outlooks website and subscribe to Climate Outlooks to stay on top of what’s happening with the climate. A complete set of Climate Summaries covering May and autumn 2018 will be available on 1 June.

Jonathan Pollock, Climatologist, Australian Bureau of Meteorology and Andrew B. Watkins, Manager of Long-range Forecast Services, Australian Bureau of Meteorology

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

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Ocean heat waves and weaker winds will keep Australia warm for a while yet


Jonathan Pollock, Australian Bureau of Meteorology; Andrew B. Watkins, Australian Bureau of Meteorology, and Catherine Ganter, Australian Bureau of Meteorology

The Australian Bureau of Meteorology’s latest climate outlook, issued today, suggests the above-average warmth of April is likely to extend into May, and for parts of the south, potentially into winter.

The outlooks for May temperatures show that both days and nights are likely to be warmer than average for much of Australia. Only northeast Queensland is likely to miss out on warmer temperatures, with no strong push there towards warmer or cooler conditions.

The unseasonable warmth, which has broken records in Adelaide and Sydney, appears to be driven by high ocean temperatures, and weaker westerly winds and much lower than average soil moisture across southern Australia.


Bureau of Meteorology

The rainfall outlook for May is mixed, but generally shows no strong shift towards a wetter or drier month for most of Australia.




Read more:
Winter heatwaves are nice … as extreme weather events go


By June the tendency for warmer than normal days may start to wane. This easing of the outlook for above average temperatures as we head into winter is reflected in the full May-July outlook, with only some parts of southern Australia likely to be warmer than average. Southern parts of Western Australia and South Australia have a moderate chance of warmer than average daytime temperatures, with stronger odds over southern Victoria.

The full May to July outlook shows a more balanced picture, with southern Australia more likely to experience higher than average temperatures.
Bureau of Meteorology

Odds don’t favour a strong push towards a particularly wet or dry three months for much of Australia, apart from some areas in the far southeast.

What’s behind the warmth?

The El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are two of Australia’s major climate drivers. ENSO is currently in a neutral phase, meaning its neither El Niño nor La Niña. Our outlooks suggest it is likely to stay neutral leading into winter.




Read more:
Explainer: El Niño and La Niña


The IOD is also neutral, and most models suggest it will remain so over the coming months.

But given it is harder to forecast ENSO and the IOD in autumn compared to other times of the year, climatologists will be monitoring Indian and Pacific Ocean temperature patterns closely as we edge towards winter.

With near-average temperature patterns in the tropical oceans to our east and west, there is no strong shift in the outlook towards widespread wetter or drier conditions for Australia.

Rainfall during May is expected to remain essentially average.
Bureau of Meteorology

However, for temperatures it’s a little different. Sure ENSO and the IOD are playing a minor role right now, but other factors are coming into play.




Read more:
The BOM outlook for the weather over the next three months is ‘neutral’ – here’s what that really means


Ocean heat waves

Ocean temperatures in the Tasman Sea and around New Zealand are much warmer than average – in fact at record levels in the past few months – and are expected to remain warm over the coming months. These warm sea temperatures are associated with a large area of lower than usual air pressure to Australia’s east, which is likely to weaken the westerly winds that normally bring cooler air to southern Australia in autumn and winter.

Another factor in the current and forecast warmth is the very much below average soil moisture across southern Australia. With little moisture available to evaporate and cool the air, and the soils themselves not able to store as much heat, the air above the ground heats more rapidly in the daytime.


Bureau of Meteorology

In addition to our natural climate drivers, Australian climate patterns are being influenced by the long-term trend in global air and ocean temperatures. Winter maximum temperatures have increased by 1℃ over the past century, with three of the top five warmest winters in the past 108 years occurring since 2009. Oceans around Australia have warmed by slightly more, with four of our top five warmest years since 2010.

The ConversationSo while the normal big two drivers of our climate remain benign, it would actually be wrong to assume there will be a quick return to more average temperatures. The outlook released today suggests we may have to wait at least another month until service returns to normal for much of the country.

Jonathan Pollock, Climatologist, Australian Bureau of Meteorology; Andrew B. Watkins, Manager of Long-range Forecast Services, Australian Bureau of Meteorology, and Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology

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

Australia’s 2017 environment scorecard: like a broken record, high temperatures further stress our ecosystems



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It was a hot year for many Australians.
ABCNews/David McMeekin

Albert Van Dijk, Australian National University and Madeleine Cahill, CSIRO

While rainfall conditions were generally good across Australia in 2017, record-breaking temperatures stressed our ecosystems on land and sea, according to our annual environmental scorecard. Unfortunately, it looks like those records will be broken again next year – and again in the years after that.

Indicators of Australia’s environment in 2017 compared to the previous year. Similar to national economic indicators they provide a summary, but also hide regional variations, complex interactions and long-term context.

National Scorecard

Our terrestrial environment has done relatively well in 2017, mainly thanks to good rainfall and leftover soil moisture from the year before. However, such a short summary for a country the size of a continent is bound to hide large regional differences. 2017 was no exception.

Western Australia and the Northern Territory received good rains, with vegetation growth, river flows and wetland area all coming in above average. By contrast, Queensland and particularly New South Wales saw a reversal of the previous year’s gains.

Environmental Condition Score in 2017 by state and territory. The large number is the score for 2017, the smaller number the change from the previous year.
Based on data on http://www.ausenv.online

Climate change is here to stay

There was good news and bad news for our atmosphere in 2017. Humanity’s collective action to fix the hole in the ozone layer is proving successful. The hole is the smallest it has been since 1988.

On the other hand, global carbon dioxide concentrations rose again, by 0.5%. While this was less than in the previous two years, it was still far from enough to stop accelerating global warming.

Globally, 2017 was the second-warmest year on record after 2016. It was the third-warmest year for Australia, and the hottest year on record in southern Queensland. These statistics are all the more remarkable because 2017 was not an El Niño year, during which high temperatures more commonly occur.

The world’s oceans were the hottest they’ve been since measurements started. Sea levels rose by 6.4mm, and sea ice cover at the poles reached another record low. In short, our planet is warming.




Read more:
Climate change’s signature was writ large on Australia’s crazy summer of 2017


The main events

Last year broke the most high-temperature records since 2009, which was at the height of the Millennium Drought – the worst drought since European settlement.

Queensland and northern New South Wales were affected most, with summer heatwaves in February and a second round of bleaching on the Great Barrier Reef. In March, Cyclone Debbie rammed into the Great Barrier Reef and the Queensland coast, bringing torrential rains and widespread flooding in its wake. The cyclone helped cool down the shallow reef waters but also ravaged delicate corals in its path, stirred up sediment and caused rivers to flush more damaging sediment and nutrients out to sea.

Winter was dry and the warmest on record and September also set heat records. Experts predicted the risk of a bad summer fire season, which did not happen, thanks to a combination of mild weather and well-timed rainfall. Nationally though, the number and size of fires were still above average, mainly due to good growing conditions in WA’s arid rangelands.

Tree growth hides loss of forests

Perhaps the most recognisable impact on our terrestrial ecosystems is the disappearance of mature vegetation after fire, drought or land clearing. We should have good data on such important changes, but we don’t.

Australia is large and poorly surveyed, so national mapping relies on satellite image interpretation. We used machine-learning algorithms to update national forest maps with more recent satellite images. These updated maps estimate a nationwide increase in forest area of 510,000ha, roughly the size of Kangaroo Island.

However, this increase is the difference between much larger gains and losses. Most of the forest increases occurred in dry woodlands in NSW and Queensland, most likely due to regrowth after a relatively wet 2016.

Unfortunately, these numbers do not paint a clear picture of the state of our ecosystems. Far more is lost from removing a hectare of dense native forest than is gained from a hectare of regrowth or new planting.

The current national mapping is insufficient to make these distinctions. We now have the satellite mapping data and technologies to do a better job. This should be a priority if we are to understand how our environment is changing and meet our international commitments.

Australia’s Environment Explorer (http://www.ausenv.online) provides summaries of environmental condition by location or region. This example shows local government areas where vegetation cover in 2017 was above average (blue colours) or below average (red colours).

Slow changes can still be deadly

While our climate is clearly changing, it is less clear how rising temperatures are impacting on our ecosystems. Many of our species are well adapted to heat, so the effects of slowly rising temperatures may go unnoticed until it is too late.

Temperatures in excess of 42℃ can kill large numbers of flying foxes, and this happened again in 2017. We know this because they roost together in their thousands and we can count the corpses under the trees.

What heat stress does to other species is far less known. There is evidence of koalas and some large birds suffering from hot days, but we barely understand how increasing temperatures may be chipping away at the cornerstones of our ecosystems: plants, bacteria, fungi, insects and other uncharismatic creatures.

At sea, we can see the impact of high sea temperatures through coral bleaching, visible even from space. Sea surface temperatures also reached record highs off the coast of southeast Australia for the second year in a row.

On top of the steady rise of ocean temperature, sea level and acidity, the East Australian Current is strengthening and reaching ever further into the Tasman Sea. The current carries tropical reef species to Sydney and yellowtail kingfish to Tasmania. The warmer water also ravages the remaining kelp forests and stresses Tasmania’s abalone, oyster and salmon industries.

The future is already here

Last year made it abundantly clear that climate change is here now, and here to stay. We will be seeing new heat records for years to come and, sadly, some species and ecosystems are unlikely to survive the onslaught.

But there are still things we can do to limit the damage. Reducing carbon emissions will still help limit future warming. Avoiding the destruction of native ecosystems should be a no-brainer.

That isn’t just about clearing farm land, which is often singled out. Australia’s population has grown by 31% since 2000. We’re adding the equivalent of a city the size of Canberra every year.

The ConversationEach of us uses space, infrastructure and resources and produces waste at levels far above the global average. If we want our land and oceans to support our privileged lifestyle in future, we have to learn to tread more lightly, and learn it fast.

Albert Van Dijk, Professor, Water and Landscape Dynamics, Fenner School of Environment & Society, Australian National University and Madeleine Cahill, Oceanographer, CSIRO

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

Too wet? Too cold? Too hot? This is how weather affects the trips we make


Jonathan Corcoran, The University of Queensland; Dorina Pojani, The University of Queensland; Francisco Rowe, University of Liverpool; Jiangping Zhou, University of Hong Kong; Jiwon Kim, The University of Queensland; Ming Wei, The University of Queensland; Sui Tao, Chinese University of Hong Kong; Thomas Sigler, The University of Queensland, and Yan Liu, The University of Queensland

What sorts of weather lead us to change our daily travel behaviour? How do we respond to scorching heatwaves, sapping humidity, snow and frost, strong winds, or torrential rain? International research shows weather is important in shaping our everyday movements.

The research evidence suggests that bad weather can lead to planned journeys being rescheduled, rerouted or cancelled. The consequences of these shifts in daily travel choices can include increases in traffic congestion and accidents, travel delays, mental stress, environmental pollution and general travel dissatisfaction.

Because people who travel by bike or walking are most likely to change travel plans in bad weather, some cities are responding with innovations such as heated bicycle lanes and sheltered walkways.




Read more:
This is how Sydney’s transport system has gone off the rails


Why do we care about the weather?

Firstly, how do we explain people’s common obsession with the weather? As Samuel Johnson put it:

It is commonly observed, that when two Englishmen meet, their first talk is of the weather; they are in haste to tell each other, what each must already know, that it is hot or cold, bright or cloudy, windy or calm.

Is this merely a keen (or indeed pathological) interest in the subject?

According to Kate Fox, these conversations are not really about the weather at all: weather-speak is a form of code, evolved to help Anglo-Australian people overcome their natural reserve and actually talk to one another. Weather-speak can be used as a greeting, as an ice-breaker, and/or as a “filler” subject.

But, beyond its use as a conversation prop and social bonding device, weather does play a major role in travel behaviour. And as the impacts of climate change unfold, the severity and frequency of extreme weather conditions are predicted to increase.

Walking across the street calls for caution during an icy winter storm in Chicago.
vonderauvisuals/Flickr, CC BY-NC-ND

A better understanding of the dynamics of the relationship between weather and travel behaviour is thus essential in helping cities develop transport and planning responses appropriate to their conditions.




Read more:
Here’s what bike-sharing programs need to succeed


What do we know about the weather-travel relationship?

It’s complicated. Research on the weather-travel relationship has revealed that effects vary by mode of travel.

Active transport, such as walking and cycling, is the most vulnerable to variations in the weather. Arriving drenched is both uncomfortable and impractical, so we might drive rather than face this prospect. Wet weather forecasts are likely to trigger a travel mode shift as travellers opt for greater comfort and safety.

But the day of the week also affects these decisions. Inclement weather is more likely to reduce weekend and off-peak travel – the so-called discretionary trips – than standard weekday commute trips. Clearly, travel purpose plays a stronger role than weather.

Significant variation exists in the effects of weather on trip-makers with different individual characteristics and household composition. For example, commuters with children are less likely to alter their travel because of the weather. This is possibly due to their household responsibilities.

Geographic variations across the transit network have been observed too. Bad weather has more serious effects in areas with less frequent services and without protected bus and rail stops. Travellers in areas with more frequent services and well-designed shelters appear to be less sensitive to bad weather.

High-density cities appear to reduce the impacts of weather on active transport, with this cyclist braving the rain in Osaka.
Akuppa John Wigham/Flickr, CC BY

In areas with high population densities, the effect of weather also appears to weaken. This is particularly the case for active transportation such as cycling.

How we travel during inclement weather also involves more subtle changes. Trip chaining, or the process of stringing together multiple smaller journeys into a larger one, is reduced in complexity, particularly on rainy days.

In terms of “extreme” weather, not all types have the same effect. Heavy precipitation (snow or rain) and, to a lesser extent, extremely high or low temperatures appear to have a greater effect on travel behaviour than strong winds or high humidity.

Adapting to weather conditions

We cannot change the weather. But we can plan our transport systems to be more resilient and better shield us from the weather when we travel.

If we don’t do this, we will face the same crisis as Transport for London. Since its privatisation, its train services experience delays every autumn and winter due to “leaves on the line” and “the wrong type of snow”.




Read more:
Why does a bit of snow plunge Britain into transport chaos?


Heavy snow can stop traffic altogether, as in New York in winter 2010.
Chris Ford/Flickr, CC BY-NC

What kind of transport adaptations are available and work? The options range from offering passengers a more diverse choice of modes, to improving existing infrastructure. For example, making public transport stations more user-friendly could soften the impact of bad weather.

More seamless interchanges may have a strong effect, as commuters generally find modal transfers stressful. Temperature-controlled, covered or underground transfer stations would protect passengers while between modes of transport.

Active travel infrastructure is particularly important. Cities that are committed to supporting non-motorised transport have implemented or proposed bold policies.

We see examples of this around the world. Increasingly hot Madrid is covering itself in trees to assist pedestrians. Frosty Dutch cities are testing heated bicycle lanes. Arid Doha has floated the idea of cooled bicycle paths. And Singapore plans to expand the city’s network of sheltered walkways.

Projecting roofs and porticoes shield us from the hot sun or precipitation. Vegetation lessens the impacts of both cold wind in temperate and subpolar latitudes and hot sunshine elsewhere.

People out and about in the hot weather of Perth welcome shade and cooling fountains.
Traveller_40/Flickr, CC BY-NC-ND

Beyond these incremental interventions, a fundamental rethink of our urban design approach is necessary. The key to limiting and adapting to the effects of weather on travel may well be the “30-minute city”. But this can only be achieved through high densities and mixed land use – concepts that have so far generated fierce resistance and NIMBYism in Australia.




Read more:
’30-minute city’? Not in my backyard! Smart Cities Plan must let people have their say


The ConversationAnother word of caution. What works in one climate zone might not work in another. This is because human bodies and minds adjust and develop different expectations and tolerance to weather and temperature patterns. For example, the optimal temperature range for cycling is as broad as 4-40°C in continental climates, but as narrow as 15-32°C in subtropical climates.

Jonathan Corcoran, Professor, School of Earth and Environmental Sciences, The University of Queensland; Dorina Pojani, Senior Lecturer in Urban Planning, The University of Queensland; Francisco Rowe, Lecturer in Quantitative Human Geography, University of Liverpool; Jiangping Zhou, Associate Professor, Department of Urban Planning and Design, University of Hong Kong; Jiwon Kim, Lecturer in Transport Engineering, The University of Queensland; Ming Wei, PhD Candidate, The University of Queensland; Sui Tao, Postdoctoral Research Fellow, Institute of Future Cities, Chinese University of Hong Kong; Thomas Sigler, Lecturer in Human Geography, The University of Queensland, and Yan Liu, Associate Professor, School of Earth and Environmental Sciences, The University of Queensland

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

The BOM outlook for the weather over the next three months is ‘neutral’ – here’s what that really means



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It’s more important to know whether there’ll be any weather than what the weather will be.
Photo by Loren Gu on Unsplash, CC BY-SA

Andrew B. Watkins, Australian Bureau of Meteorology and Felicity Gamble, Australian Bureau of Meteorology

Today the Bureau of Meteorology releases its end-of-month seasonal outlook for April to June, updating the initial outlook released on March 15. But you might not have seen much media coverage of it, because we’re not seeing big swings towards the attention-grabbing climate drivers like El Niño or the Indian Ocean Dipole, which can dominate Australia’s climate.




Read more:
Dipole: the ‘Indian Niño’ that has brought devastating drought to East Africa


There are times when the main drivers of our climate are not strong enough to push us towards a season dominated by unusually wet or dry, or hot or cool, weather. This can also happen if different climate drivers are having opposite impacts – they can cancel each other out.

Without a strong push one way or another, our outlook maps are often white. This is a neutral or “50:50” outlook map.

The rainfall outlook map for April–June 2018, issued March 15 (left), shows most of Australia in the neutral/50:50 range (so coloured white). In contrast, the rainfall outlook map for October 2015 (right) shows a low chance of exceeding the median (so brown dominates the map).
Bureau of Metereology

A 50:50 outlook map doesn’t mean we’re taking a guess, or that there’s no indication of what’s happening with our weather and climate. In fact, it’s giving us some key information.

What does a neutral outlook mean?

Let’s focus on rain. A neutral climate outlook means there is a 50% chance of above-average rainfall. In other words, there is an equal chance of getting above-average or below-average rain over the coming season.

But it doesn’t mean that the most likely rainfall is spot-on average. Have a look at the graph below for rainfall in the Murray—Darling Basin. It shows rainfall over 116 years, ordered from lowest to highest. Years with no strong climate driver, or no strong push from the climate system one way or another, are in blue.


Bureau of Meteorology

Most winter–spring periods (29 out of the 40 years, or about three-quarters of all years) fall within the middle 50% of past rainfall totals, as indicated by the 25th and 75th percentile lines. But within that middle 50%, the rainfall in neutral years is fairly evenly spread — it isn’t clustered right in the middle, or dead on average.

This means two things.

First, it means that a neutral year will typically bring quite variable rainfall, with periods of rainfall above or below average. We also know that the above or below patterns tend not to be as widespread across the continent as during stronger La Niña or El Niño periods.

Second – and importantly – it also means there is less chance of extremely wet or extremely dry conditions over large areas; that’s a good sign if drought or flood is a concern.

What doesn’t a neutral outlook mean?

A neutral outlook certainly doesn’t mean climatologists are having a bet each way. We can think about this in terms of a football game.

Some footy games we are fairly sure will be a one-sided affair — based on previous match performance, players’ injuries, whether it’s a home or away game, and so on. On other occasions, those factors aren’t in play and the teams are very evenly matched, so the result could go either way. It doesn’t mean we don’t know much about footy or about the teams that are about to play – it’s just that there is no strong indication that one team is far better than the other.




Read more:
A chaotic beast, probably: wacky weather and climate forecasting


What can I do with a neutral outlook?

So what should you look at during neutral periods to get an idea of what’s possible for the upcoming season? Well, there’s lots of additional information on our climate outlooks website.

For a start, think about your local rainfall at a particular time of year, and what range you typically have in years without flood or drought. Use our rainfall ranges information to see your current rainfall accumulation, and what result you’ll get in a few months’ time if a typical range (wet, dry or average) of rain falls over the season.

The seasonal outlook itself may also be useful. For example, if you need a certain amount of rainfall, say 100mm over the next season, you can check out the likelihood of that happening. Or looking at it the other way round, what rainfall amount has a 25% (less likely) or 75% (more likely) chance of occurring, as shown below.

BOM seasonal outlook.

Other tools worth worth looking at in neutral periods include streamflow forecasts, which can tell you if streamflows are likely to be high, low or average in your region, and soil moisture guidance, to assess your soil moisture for daily and monthly periods.

And, of course, you can find the typical rainfall range for your area in our Climate Data Online. Select “Weather and Climate” at the top and “Monthly” statistics.

BOM Climate Data Online.

All of us – including climatologists – wish the outlooks were always clearly wet or dry, or hot or cool. It would certainly make all our lives a lot easier! But when the climate drivers are not strong, or oppose each other, there’s rarely any chance of a big push towards one outcome – and that information is still useful for making decisions.

A neutral outlook indicates a 50% chance of above-average rainfall. This means there is more chance of good rain than in a season with only 25% probability, but less chance than a season with 75%.

If your appetite for risk is high – if you are a farmer with good soil moisture, full dams and lots of money in the bank – 50% may be enough for you to take a punt on a riskier crop. But if times are tough, 50% may not be anywhere near high enough, so you’d make a more conservative decision. No number is ever too small if the return is high enough: most of us have bought a lottery ticket even though the odds might be one in a million.




Read more:
Curious Kids: What causes windy weather?


At the end of the day, a 50% chance is a number just like any other. When combined with your knowledge of what a typical range of outcomes may be, other bureau information at your fingertips, and your appetite for risk, it can still help you make a climate-smart decision.


You can stay on top of what’s happening with the climate by subscribing to the Bureau of Meteorology’s Climate Outlooks.

The ConversationThis is an edited version of a post that appeared on the Bureau of Meteorology’s blog.

Andrew B. Watkins, Manager of Long-range Forecast Services, Australian Bureau of Meteorology and Felicity Gamble, Senior climatologist, Australian Bureau of Meteorology, Australian Bureau of Meteorology

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

Making climate models open source makes them even more useful



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MiMA: an open source way to model the climate.
Martin Jucker, Author provided

Martin Jucker, University of Melbourne

Designing climate experiments is all but impossible in the real world. We can’t, for instance, study the effects of clouds by taking away all the clouds for a set period of time and seeing what happens.

Instead, we have to design our experiments virtually, by developing computer models. Now, a new open-source set of climate models has allowed this research to become more collaborative, efficient and reliable.




Read more:
Why scientists adjust temperature records, and how you can too


Full climate models are designed to be as close to nature as possible. They are representations of the combined knowledge of climate science and are without a doubt the best tools to understand what the future might look like.

However, many research projects focus on small parts of the climate, such as sudden wind changes, the temperature in a given region, or ocean currents. For these studies, concentrating on a small detail in a full climate model is like trying to find a needle in the haystack.

It is therefore common practice in such cases to take away the haystack by using simpler climate models. Scientists usually write these models for specific projects. A quote commonly attributed to Albert Einstein maybe best summarises the process: “Everything should be made as simple as possible, but not simpler.”

Here’s an example. In a paper from last year I looked at the temperature and wind changes in the upper atmosphere close to the Equator. I didn’t need to know what happened in the ocean, and I didn’t need any chemistry, polar ice, or even clouds in my model. So I wrote a much simpler model without these ingredients. It’s called “MiMA” (Model of an idealised Moist Atmosphere), and is freely available on the web.

MiMA.

The drawbacks of simpler models

Of course, using simpler models comes with its own problems.

The main issue is that researchers have to be very clear what the limits are for each model. For instance, it would be hard to study thunderstorms with a model that doesn’t reproduce clouds.

The second issue is that whereas the scientific results may be published, the code itself is typically not. Everyone has to believe that the model does indeed do what the author claims, and to trust that there are no errors in the code.

The third issue with simpler models is that anyone else trying to duplicate or build on published work would have to rebuild a similar model themselves. But given that the two models will be written by two (or more) different people, it is highly unlikely that they will be exactly the same. Also, the time the first author spends on building their model is then spent a second time by a second author, to achieve at best the same result. This is very inefficient.

Open-source climate models

To remedy some (if not all) of these issues, some colleagues and I have built a framework of climate models called Isca. Isca contains models that are easy to obtain, completely free, documented, and come with software to make installation and running easier. All changes are documented and can be reverted. Therefore, it is easy for everyone to use exactly the same models.

The time it would take for everyone to build their own version of the same model can now be used to extend the existing models. More sets of eyes on one model means that errors can be quickly identified and corrected. The time saved could also be used to build new analysis software, which can extract new information from existing simulations.

As a result, the climate models and their resulting scientific experiments become both more flexible and reliable. All of this only works because the code is publicly available and because any changes are continuously tracked and documented.

An example is my own code, MiMA, which is part of Isca. I have been amazed at the breadth of research it is used for. I wrote it to look at the tropical upper atmosphere, but others have since used it to study the life cycle of weather systems, the Indian monsoon, the effect of volcanic eruptions on climate, and so on. And that’s only one year after its first publication.




Read more:
Climate models too complicated? Here’s one that everyone can use


Making models openly available in this way has another advantage. Using an accessible proof can counter the mistrust of climate science that is still prevalent in some quarters.

The burden of proof automatically falls on the sceptics. As all the code is there and all changes are trackable, it is up to them to point out errors. And if someone does find an error, even better! Correcting it is just another step to make the models even more reliable.

The ConversationGoing open source with scientific code has many more benefits than drawbacks. It allows collaboration between people who don’t even know one another. And, most importantly, it will make our climate models more flexible, more reliable and generally more useful.

Martin Jucker, Maritime Continent Research Fellow, University of Melbourne

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