“It’s so beautiful! But you can also see tiny details in the clouds that impact the amount of light they let through,” says Ekman, professor of meteorology at Stockholm University.

She opens a photo on her computer. It was taken in the Arctic, the large area of sea and land surrounding the North Pole. Swirling clouds billow over the white polar ice. The sun is low in the sky and fissures in the ice reveal dark sea water.

As a Wallenberg Scholar, Ekman wants to ascertain the impact polar clouds have on global warming. To this end, she is developing a new mathematical model that describes how clouds are formed.

Clouds can cool or warm

Clouds play a key role in the global climate. They can have a cooling effect by blocking out sunlight, or a warming one by preventing the Earth’s heat from escaping. The extent to which clouds have a warming or cooling effect depends on factors such as their shape, altitude and water content.

Overall, clouds currently have a cooling effect on the Earth’s surface. But most current climate models suggest their cooling effect will diminish in a warming climate. This is uncertain, however, not least as regards clouds over the polar regions. Ekman elaborates:

“We know fairly little about clouds in the polar regions, and they are oversimplified in the climate models. This is partly because cloud descriptions are based on measurement data from other parts of the world.”

Cloud formation is the result of complex processes in which small- and large-scale phenomena interact. On the small scale there are physical processes in which water vapor condenses to form cloud droplets. Cloud development is simultaneously impacted by large-scale movements in the atmosphere, such as air currents and temperature variations. These processes cannot be described precisely in climate models; they have to be simplified in various ways.

To date, in the absence of meteorological data from the Arctic and Antarctic, researchers have based these simplified descriptions on data from other climate zones. They have done so even though environmental conditions in the polar regions are unique, and cloud formation is therefore different there.

In recent years, Swedish and foreign researchers have greatly increased measurements in the polar regions. There are also satellites orbiting the Earth, gathering data that is highly relevant to clouds and their properties. Ekman considers that the time is ripe to use all this information.

Building better cloud models

Her research involves developing a new numerical model that describes cloud formation in the Arctic and Antarctic more directly and in greater detail than previously. The model includes processes that are otherwise usually ignored. The simplifications that must be made are being done better. The research team is comparing the model with the real-life situation using the monitoring and satellite data that are now available on the Arctic and Antarctic.

“These radar measurements reveal the presence of a cloud, which gradually rises, and in the simulation below we see that the model captures this as well,” says Ekman, showing results where the team has compared an early version of the cloud model with data from radar monitoring.

The Arctic is warming up dramatically. I want to find out whether clouds are playing a part in this.

Among other things, the new model will include an improved description of aerosols. These are airborne particles that are needed for clouds to form. They impact both the quantity of cloud droplets formed and how well clouds reflect sunlight. The model also takes account of interactions between clouds and the sea and ice surface.

The research team will be paying particular attention to the situations where warm air enters the area or cold air leaves it, since this is when most cloud formation in the Arctic takes place. The model also enables them to examine how clouds are impacted by factors that change in a warmer climate, such as the quantity of airborne particles and large-scale winds.

Gathering a range of expertise

Integrating different aspects of cloud formation in the way that Ekman is doing is no easy task. Meteorologists have traditionally focused on large-scale dynamics, and physicists and chemists have concentrated on the details. Ice modeling specialists have confined their studies to ice and oceanographers to the sea. But Ekman believes that collaboration is the route to progress.

“You can’t isolate the atmosphere or the sea from their surroundings. That’s what is so enjoyable about atmospheric research – the fact that so many elements are involved. I’m also glad I’ve been able to recruit a scientific programmer, who is working on the technical aspects of the model. It’s a really important job.”

The type of model that Ekman is developing is usually used to study processes in a limited area: approximately 10 kilometers x 10 kilometers. One vital task is to upscale the model without losing important information. The team is aiming to achieve the scale used in global climate models: 100 kilometers x 100 kilometers.

“We now have so much computational capacity that it ought to work. This will enable us to compare the global models with our detailed model and see if we can make them better, so we can make more reliable projections about the future climate,” she says.

Text Sara Nilsson
Translation Maxwell Arding
Photo Magnus Bergström