Tag Archives for dry

The winter was dry, the spring will likely be dry – here’s why


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

Winter still has a few days to run, but it’s highly likely to be one of Australia’s warmest and driest on record. While final numbers will be crunched once August ends, this winter will probably rank among the top ten warmest for daytime temperatures and the top ten driest for rainfall.

While it was drier than average across most of the country, it was especially dry across South Australia, New South Wales and southern Queensland. Small areas of South Australia and New South Wales are on track for their driest winter on record.



Read more:
Recent Australian droughts may be the worst in 800 years

In contrast, parts of southern Victoria, western Tasmania and central Queensland were wetter than usual.

Preliminary winter 2019 rainfall deciles.
Bureau of Meteorology

Thirsty ground

Soil moisture normally increases during winter (except in the tropics, where it’s the dry season), and while we saw that in parts of Victoria, for most of Queensland and New South Wales the soil moisture actually decreased.

Dry soils leading into winter have soaked up the rain that has fallen, resulting in limited runoff and inflows into the major water storages across the country.

A glass half empty

Sydney’s water storages dropping below 50% received considerable public attention, and unfortunately a number of other regional storages in New South Wales and the Murray Darling Basin are much lower than that.

The winter ‘filling’ season in the southern Murray Darling Basin has been drier than usual for the third year in a row, and storages in the northern Murray Darling basin are extremely low or empty with no meaningful inflows.

Some rain in the west

Some regions did receive enough rainfall to grow crops this cool season. However, northern New South Wales and southern Queensland didn’t see an improvement in their severe year-to-date rainfall deficiencies over winter.

In fact, the area of the country that is experiencing year-to-date rainfall in the lowest 5% of historical records expanded.

In better news, the severe year-to-date deficiencies across southwest Western Australia shrank during winter.

Indian Ocean Dipole the culprit

Sustained differences between sea surface temperatures in the tropical western and eastern Indian Ocean are known as the Indian Ocean Dipole (IOD). The IOD impacts Australian seasonal rainfall and temperature patterns, much like the more well known El Niño–Southern Oscillation.

Warm sea surface temperatures in the tropical western Indian Ocean and cool sea surface temperatures in the eastern Indian Ocean, along with changes in both cloud and wind patterns, have been consistent with a positive Indian Ocean Dipole since late May.

International climate models, some of which forecast the positive IOD as early as February, agree that it is likely to continue through spring.

Typically, this means below average rainfall and above average temperatures for much of central and southern Australia, which is consistent with the current rainfall and temperature outlook from the Bureau’s dynamical computer model. The positive IOD is likely to be the dominant climate driver for Australia during the next three months.

Comparison of international climate model forecasts of the IOD index for November 2019.
Models from the Australian Bureau of Meteorology, Canadian Meteorological Centre, European Centre for Medium-Range Weather Forecasts, Meteo France, National Aeronautics and Space Administration (USA) and the Met Office (UK)

A dry end to 2019 likely

Chances are the remainder of 2019 will be drier than normal for most of Australia. The exceptions are western Tasmania, southern Victoria and western WA, where chances of a wetter or drier than average end to the year are roughly equal.

The spring 2019 outlook showing low chances of above average rainfall for most of the country.
Bureau of Meteorology

Warmer than average days are very likely (chances above 80%) for most of the country except the far south of the mainland, and Tasmania.

Nights too are likely to be warmer than average for most of the country. However, much of Victoria and Tasmania, and southern parts of South Australia and New South Wales have close to an even chance for warmer than average minimum temperatures.

Due to the warm and dry start to the year, the east coast of Queensland, New South Wales, Victoria and Tasmania, as well as parts of southern Western Australia, face above normal fire potential this coming bushfire season.

More outlooks more often

The term weather describes conditions over shorter periods, such as from minutes to days, while the term climate describes the more slowly varying aspects of the atmosphere.

From today, the Bureau of Meteorology is closing the forecast gap between weather and climate information with the release of weekly and fortnightly climate outlooks.

For the first time, rainfall and temperature outlooks for the weeks directly after the 7-day forecast are available. One- and two-week outlooks have been added to complement the existing 1-month and 3-month outlooks.



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The new outlook information for the weeks ahead also features how much above or below average temperatures are likely to be, and the likelihood of different rainfall totals.

The Bureau’s outlook videos explain the long-range forecast for the coming months.
Bureau of Meteorology

You can find climate outlooks and summaries on the Bureau of Meteorology website here.The Conversation

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

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

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Dry lightning has set Tasmania ablaze, and climate change makes it more likely to happen again


Nick Earl, University of Melbourne; Peter Love, University of Tasmania; Rebecca Harris, University of Tasmania, and Tomas Remenyi, University of Tasmania

Every year Tasmania is hit by thousands of lightning strikes, which harmlessly hit wet ground. But a huge swathe of the state is now burning as a result of “dry lightning” strikes.

Dry lightning occurs when a storm forms from high temperatures or along a weather front (as usual) but, unlike normal thunderstorms, the rain evaporates before it reaches the ground, so lightning strikes dry vegetation and sparks bushfires.

Dangerous, large fires occur when dry lightning strikes in very dry environments that are full of fuel ready to burn. Cold fronts in Tasmania, which often carry fire-extinguishing rain, have recently been dry, making these fires worse. The fronts draw in strong hot, dry northerly winds, fanning the flames.



Read more:
Fires in Tasmania’s ancient forests are a warning for all of us

Research has found that as climate change creates a drier Tasmania landscape, dry lightning – and therefore these kinds of fires – are likely to increase.

History and detection in Tasmania

Lightning has always started fires across Tasmania. Fire scars and other paleo evidence across Tasmania show large fires are a natural process in some places. However, frequent large, intense fires were rare. Now such fires are being fought almost every year.

Contrary to anecdotal belief, our recent preliminary work suggests that lightning activity has not increased over recent decades. So why do fires started by lightning appear to be increasing?

As temperatures rise, evaporation rates are increasing, but current rainfall rates are about the same. In combination this means the Tasmanian landscape is drying. The landscape is more often primed, waiting for an ignition source such as a dry-lightning strike. In such conditions, it only takes one.

When dry lighting strikes

Lightning struck just such a landscape in late December 2018, starting the Gell River bushfire in southwest Tasmania. This uncontrollable fire burnt about 20,000 hectares in the first half of January and is still burning. These large fires deplete the state’s resources, fatigue our volunteer and professional fire fighters and can have disastrous effects on natural systems.

With no significant rain falling over Tasmania since mid-December, the island is breaking dry spell records and thousands of dry lightning events have occurred. On January 15 alone over 2,000 lightning strikes sparked more than 60 bushfires.

Most of these were controlled rapidly, a credit to Tasmania’s emergency responders. One of the worst-hit areas was the Tasmanian Wilderness World Heritage Area, where many bushfires continue to burn in inaccessible locations.

This is putting some of Tasmania’s most pristine and valuable places in danger of being lost. The state stands to lose its most remarkable old-growth forests, like Mount Anne, which is home to some of the world’s largest King Billy Pines, a species endemic to Tasmania.

Increasing dry area

Ongoing climate change is making dry spells longer and more frequent, increasing the fire-prone area of Tasmania. Almost the whole state is becoming vulnerable to dry lightning.

Some regions of the west coast of Tasmania used to have very little to no risk of bushfires as they were always damp. However, this is no longer the case, resulting in species coming under threat.

Unlike most of Australia’s vegetation, many of Tasmania’s alpine and subalpine species evolved in the absence of fire and therefore do not recover after being burnt. Endemic species like Pencil Pine, Huon Pine and Deciduous Beech may be wiped out by one fire.

So what does the future hold? Using data from Climate Futures for Tasmania, we can peek into the future. Our models indicate that climate change is highly likely to result in profound changes to the fire climate of Tasmania, especially in the west.

Climate change already playing a role

With a warming climate, the rain-producing low-pressure systems are moving south and many storms that used to hit Tasmania are drifting south, leaving the island drier. This, combined with increasing evaporation rates, result in rapid drying of some areas. Areas that historically rarely experienced fire will become increasingly prone to burn. The drying trend is projected to be particularly profound throughout western Tasmania.

By the end of the century, summer conditions are projected to last eight weeks longer. This drying means that lightning events (and therefore dry lightning) will become an ever-increasing threat and the impact of these events will become more significant.

Higher levels of dryness will mean when bushfires occur the potential for these to burn into the rainforest, peat soils and alpine areas will be significantly increased.



Read more:
How far away was that lightning?

These changes are already happening and will get progressively worse throughout the 21st century. Climate change is no longer a threat of the future: we are experiencing it now.The Conversation

Nick Earl, Postdoctoral associate, School of Earth Sciences, University of Melbourne; Peter Love, Atmospheric Physicist, University of Tasmania; Rebecca Harris, Climate Research Fellow, University of Tasmania, and Tomas Remenyi, Climate Research Fellow, Climate Futures Group, Antarctic Climate and Ecosystems CRC, University of Tasmania

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

Why a wetland might not be wet


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Wetlands can have decades-long dry periods.
Felicity Burke/The Conversation, CC BY-SA

Deborah Bower, University of New England; Ben Vincent, University of New England; Darren Ryder, University of New England; John Thomas Hunter, University of New England; Lindsey Frost, University of New England; Manu Saunders, University of New England, and Sarah Mika, University of New England

Lake Eyre is one of Australia’s most iconic wetlands, home to thousands of waterbirds that migrate from all over Australia and the world. But it is often dry for decades between floods.

Many people think wetlands are swamps or ponds that die when dry. But unlike many places worldwide, most Australian wetlands have natural wet-dry cycles, with dry spells that can last for decades. Dry phases are necessary for the life cycle of the wetland itself, as well as for many of the plants and animals that live there.



Read more:
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So, if wetlands are still wetlands when they’re dry, how do you spot one? And what do we need to know about these unique places to protect their wonderful and unique biodiversity?

Fogg Dam wetlands in the Northern Territory are a riot of colour during monsoon season.
Geoff Whalan/Flickr, CC BY-NC

When the rains come

Floods are vital for a wetland. As one fills, water depth can increase rapidly, the temperature falls, and dissolved oxygen is high as turbulent raindrops or floodwaters fill the basin. Within a few hours of wetting, animals and plants that can tolerate the dry periods will hatch, sprout or resume life, and a new aquatic food web begins.

Algae begin blooming, the soil releases nutrients, and tiny aquatic animals like rotifers hatch from dried eggs. Within a week, copepods and other small crustaceans hatch and adult insects like dragonflies arrive to lay their eggs. Huge numbers of waterbirds may flock to the wetland to enjoy the abundant algae and crustaceans. Other critters emerge from hideouts in crayfish burrows, beneath leaf litter or buried in shallow sediment.

When wetlands flood they fill rapidly with life.
Felicity Burke/The Conversation, CC BY

After filling, new plants emerge in distinct zones depending on water depth and how often and long they are wet. Wetland plants produce oxygen and store carbon, two services essential for life on earth. They have evolved many ways to survive through dry times and thrive during the wet.

Some plants, like pondweed, are so adapted to aquatic life that a single stem can grow thin branching leaves underwater and thicker broader leaves above water. This helps the plant to access oxygen underwater while simultaneously maximising the sunlight it receives above water. Both are necessary for growth and survival.



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As the wetland dries, water temperatures increase, dissolved oxygen drops and aquatic animals either leave or prepare to survive the dry times.

Some, like mosquito larvae, have adapted to stagnant water. They breath through siphons on their tail to survive this final drying stage. Once the wetland is completely dry, microbes take over to start breaking down any remaining organic matter and the cycle starts again.

Macquarie Marshes in NSW moves between wet and dry.
Margaret Donald/Flickr, CC BY-ND

Many plants and animals in the wetland die and decompose, enriching the earth. These very fertile soils are the reason why wetlands are so often drained for cropping and grazing. If undisturbed, these nutrients are stored in the soil until the next flood. When completely dry, the wetland may only be evident as a depression of fine soil with a perimeter of sedges or reeds.

Wetlands may stay dry for many decades, while eggs and seeds wait and rest until the next flood. Some eggs (such as shield shrimp) are small enough to be dispersed by the wind, or hitch a ride on waterbirds leaving the area.

The plants, animals and microbes occupying wetlands improve the surrounding landscape, providing pollination, pest control, carbon and nutrient storage, and waste removal. Wetlands store 35% of carbon in only 9% of the earth’s surface, reducing floods and recharging groundwater. Understanding how plants and animals will adapt to the extended dry periods predicted with climate change is increasingly important.

Under dry earth, many plants and creatures wait for the rains to come again.
Felicity Burke/The Conversation, CC BY

A drying climate is particularly concerning for high altitude wetlands that are very restricted in the Australian landscape. They occur on the New England Tablelands and Monaro Plateau and can be rapidly degraded by grazing, cropping, diverting or storing water, or fires that can each destroy thousands of years of peat growth in a few days. Losing these wetlands brings us a step closer to losing threatened species such as the Giant dragonfly and Latham’s snipe that rely on these unique upland wetlands.



Read more:
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Wetlands are largely threatened by lack of understanding that the quiet dry periods fuel the booming wet periods. It is critical that we know where wetlands are in the landscape, so we can protect them during wet and dry phases. Protecting wetlands even when they’re not wet sustains vital seed and egg banks that kickstart complex food webs linking land and water across Australia’s iconic wetland ecosystems.The Conversation

Deborah Bower, Lecturer in Ecosystem Rehabilitation, University of New England; Ben Vincent, Research officer, University of New England; Darren Ryder, Professor of Aquatic Ecology and Restoration, University of New England; John Thomas Hunter, Adjunct Associate Professor in Landscape Ecology, University of New England; Lindsey Frost, Technical Officer, University of New England; Manu Saunders, Research fellow, University of New England, and Sarah Mika, Research fellow, University of New England

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

Peak Water & Food Supplies


The link below is to an article that takes a look at what is being called ‘peak water,’ as groundwater supplies begin to dry up around the world and its impact on global food supplies.

For more visit:
http://www.guardian.co.uk/global-development/2013/jul/06/food-supply-threat-water-wells-dry-up

Water Crisis: Rivers Running Dry


The following is an article reporting on the overuse of rivers and a number of rivers that are running out of water.

For more visit:
http://environment.nationalgeographic.com/environment/photos/rivers-run-dry/