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Hot Canada! How Climate Change Impacts the Weather

Professors Christian Jakob and Michael Reeder explain how heatwaves form ... and why they weather is a part of climate change we should pay closer attention to.

Hot Canada! How Climate Change Impacts the Weather
Wildfires spread in British Columbia, Canada on July 4, 2021
Christian Jakob, Michael Reeder*

Eight days ago, it rained over the western Pacific Ocean near Japan. There was nothing especially remarkable about this rain event, yet it made big waves twice.

First, it disturbed the atmosphere in just the right way to set off an undulation in the jet stream - a river of very strong winds in the upper atmosphere - that atmospheric scientists call a Rossby wave (or a planetary wave). Then the wave was guided eastwards by the jet stream towards North America. Along the way the wave amplified, until it broke just like an ocean wave does when it approaches the shore. When the wave broke it created a region of high pressure that has remained stationary over the North American northwest for the past week.

This is where our innocuous rain event made waves again: the locked region of high pressure air set off one of the most extraordinary heatwaves we have ever seen, smashing temperature records in the Pacific Northwest of the United States and in Western Canada as far north as the Arctic. Lytton in British Columbia hit 49.6℃ this week before suffering a devastating wildfire.

What makes a heatwave?

While this heatwave has been extraordinary in many ways, its birth and evolution followed a well-known sequence of events that generate heatwaves.

Heatwaves occur when there is high air pressure at ground level. The high pressure is a result of air sinking through the atmosphere. As the air descends, the pressure increases, compressing the air and heating it up, just like in a bike pump. Sinking air has a big warming effect: the temperature increases by 1 degree for every 100 metres the air is pushed downwards.

High-pressure systems are an intrinsic part of an atmospheric Rossby wave, and they travel along with the wave. Heatwaves occur when the high-pressure systems stop moving and affect a particular region for a considerable time. When this happens, the warming of the air by sinking alone can be further intensified by the ground heating the air – which is especially powerful if the ground was already dry. In the northwestern US and western Canada, heatwaves are compounded by the warming produced by air sinking after it crosses the Rocky Mountains.

How Rossby waves drive weather

This leaves two questions: what makes a high-pressure system, and why does it stop moving?

As we mentioned above, a high-pressure system is usually part of a specific type of wave in the atmosphere – a Rossby wave. These waves are very common, and they form when air is displaced north or south by mountains, other weather systems or large areas of rain.

A man cools off in Lynn Creek in North Vancouver during Canada's heatwave — Photo: Darryl Dyck/The Canadian Press/ZUMA Press

Rossby waves are the main drivers of weather outside the tropics, including the changeable weather in the southern half of Australia. Occasionally, the waves grow so large that they overturn on themselves and break. The breaking of the waves is intimately involved in making them stationary. Importantly, just as for the recent event, the seeds for the Rossby waves that trigger heatwaves are located several thousands of kilometres to the west of their location. So for northwestern America, that's the western Pacific. Australian heatwaves are typically triggered by events in the Atlantic to the west of Africa.

Another important feature of heatwaves is that they are often accompanied by high rainfall closer to the Equator. When southeast Australia experiences heatwaves, northern Australia often experiences rain. These rain events are not just side effects, but they actively enhance and prolong heatwaves.

What will climate change mean for heatwaves?

Understanding the mechanics of what causes heatwaves is very important if we want to know how they might change as the planet gets hotter.

We know increased carbon dioxide in the atmosphere is increasing Earth's average surface temperature. However, while this average warming is the background for heatwaves, the extremely high temperatures are produced by the movements of the atmosphere we talked about earlier. So to know how heatwaves will change as our planet warms, we need to know how the changing climate affects the weather events that produce them. This is a much more difficult question than knowing the change in global average temperature.

How will events that seed Rossby waves change? How will the jet streams change? Will more waves get big enough to break? Will high-pressure systems stay in one place for longer? Will the associated rainfall become more intense, and how might that affect the heatwaves themselves?

Our answers to these questions are so far somewhat rudimentary. This is largely because some of the key processes involved are too detailed to be explicitly included in current large-scale climate models.

Climate models agree that global warming will change the position and strength of the jet streams. However, the models disagree about what will happen to Rossby waves.

From climate change to weather change

There is one thing we do know for sure: we need to up our game in understanding how the weather is changing as our planet warms, because weather is what has the biggest impact on humans and natural systems.

To do this, we will need to build computer models of the world's climate that explicitly include some of the fine detail of weather. (By fine detail, we mean anything about a kilometre in size.) This in turn will require investment in huge amounts of computing power for tools such as our national climate model, the Australian Community Climate and Earth System Simulator (ACCESS), and the computing and modelling infrastructure projects of the National Collaborative Research Infrastructure Strategy (NCRIS) that support it.

We will also need to break down the artificial boundaries between weather and climate which exist in our research, our education and our public conversation.


* Christian Jakob, Professor in Atmospheric Science, Monash University and Michael Reeder, Professor, School of Earth, Atmosphere and Environment, Monash University

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

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Green

In Argentina, A Visit To World's Highest Solar Energy Park

With loans and solar panels from China, the massive solar park has been opened a year and is already powering the surrounding areas. Now the Chinese supplier is pushing for an expansion.

960,000 solar panels have been installed at the Cauchari park

Silvia Naishtat

CAUCHARI — Driving across the border with Chile into the northwest Argentine department of Susques, you may spot what looks like a black mass in the distance. Arriving at a 4,000-meter altitude in the municipality of Cauchari, what comes into view instead is an assembly of 960,000 solar panels. It is the world's highest photovoltaic (PV) park, which is also the second biggest solar energy facility in Latin America, after Mexico's Aguascalientes plant.

Spread over 800 hectares in an arid landscape, the Cauchari park has been operating for a year, and has so far turned sunshine into 315 megawatts of electricity, enough to power the local provincial capital of Jujuy through the national grid.


It has also generated some $50 million for the province, which Governor Gerardo Morales has allocated to building 239 schools.

Abundant sunshine, low temperatures

The physicist Martín Albornoz says Cauchari, which means "link to the sun," is exposed to the best solar radiation anywhere. The area has 260 days of sunshine, with no smog and relatively low temperatures, which helps keep the panels in optimal conditions.

Its construction began with a loan of more than $331 million from China's Eximbank, which allowed the purchase of panels made in Shanghai. They arrived in Buenos Aires in 2,500 containers and were later trucked a considerable distance to the site in Cauchari . This was a titanic project that required 1,200 builders and 10-ton cranes, but will save some 780,000 tons of CO2 emissions a year.

It is now run by 60 technicians. Its panels, with a 25-year guarantee, follow the sun's path and are cleaned twice a year. The plant is expected to have a service life of 40 years. Its choice of location was based on power lines traced in the 1990s to export power to Chile, now fed by the park.

Chinese engineers working in an office at the Cauchari park

Xinhua/ZUMA

Chinese want to expand

The plant belongs to the public-sector firm Jemse (Jujuy Energía y Minería), created in 2011 by the province's then governor Eduardo Fellner. Jemse's president, Felipe Albornoz, says that once Chinese credits are repaid in 20 years, Cauchari will earn the province $600 million.

The Argentine Energy ministry must now decide on the park's proposed expansion. The Chinese would pay in $200 million, which will help install 400,000 additional panels and generate enough power for the entire province of Jujuy.

The park's CEO, Guillermo Hoerth, observes that state policies are key to turning Jujuy into a green province. "We must change the production model. The world is rapidly cutting fossil fuel emissions. This is a great opportunity," Hoerth says.

The province's energy chief, Mario Pizarro, says in turn that Susques and three other provincial districts are already self-sufficient with clean energy, and three other districts would soon follow.

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