Breaking through the clouds

Scaling up

At the micro-level, cloud formation begins when air saturated with water vapour condenses around aerosols, such as grains of dust in the atmosphere. At larger scales, it means predicting and tracking cloud movements at continental levels.

“These differences in scale require huge numbers of observations and massive computing power,” Fourrié says. 

“But increasing the number and resolution of cloud observations has the potential to substantially improve everything from the prediction of thunderstorms and flash floods, to refining studies of climate change. Therefore, better characterising clouds from formation to dissipation, and from top to bottom, is a major priority for meteorologists.” 

MTG’s suite of cutting-edge instruments will enable meteorologists to better spot factors that drive the seeding of anvil-shaped cumulonimbus storm clouds, and predict their impacts on future weather and cloud formation. Observations from MTG, Metop-SG, and related programmes such as new additions to the European Union’s Copernicus satellite programme, will also help meteorologists observe and track the life cycles of all cloud types, including more common fair weather clouds such as cotton wool-like cumuliform clouds. 

“For example, we currently lack detailed satellite observations over large parts of the ocean, such as of the throughflow of humidity that often drives the genesis of thunderstorms and heavy precipitation,” Fourrié says. “Data provided by MTG will help fill these gaps, providing invaluable information for fine-detail regional scale models such as AROME (Applications of Research to Operations at MEsoscale), a numerical weather prediction model created and operated by Météo-France.

“Clouds not only make rain, sleet, and snow, they also contribute significantly to the amount of the sun’s energy that is reflected back to space, while conversely absorbing heat that radiates from the surface, preventing it from freely escaping the Earth’s atmosphere. Different clouds may have a warming or cooling effect depending on their type, height, the time of day, or the season. As they are so common, small changes in the properties of cumuliform clouds can have massive impacts on the Earth’s energy balance.

“A related challenge is that clouds are also a major source of uncertainty in climate change models and it is very important to understand them in order to better respond to global heating.” 

Scheduled for launch at the end of 2023, MTG's Infrared Sounder instrument will vastly increase the type and amount of observations available for numerical weather prediction models, Fourrié says.

“For AROME, we currently bring together around 20 different pieces of data for each assimilated observation of the imager. But MTG will provide more than 1,000 pieces of information per observation location, spanning temperature, humidity, clouds, chemical composition, and much more.

“To make good forecasts, it is necessary to have the best and most accurate observations of the initial conditions. It will be a rapid revolution because MTG will provide a huge amount of information in unprecedented detail.” 

Preparing for MTG data bounties

Teams at CNRM are already putting MTG’s future capabilities to the test, by assimilating existing data to estimate the impact of new instruments. Now, Fourrié says it is a race against time to be ready for when MTG takes to the skies. 

“It is a huge technical challenge to receive this data, and a huge scientific challenge to filter the most useful observations for our models,” she says. “We need to integrate observations from above, below, and between clouds and to build synergies between these datasets in order to better understand clouds. 

But the rewards of doing so will be immense.

“Everyone here is very excited about the upcoming launch of EUMETSAT’s next-generation satellites,” says Fourrié. “As numerical weather predictions become more precise, it will become possible to not only better predict severe weather such as very heavy rainfall, but also better characterise what that means for people living in the affected areas. Will there be floods? Which areas are going to be affected the most? How should authorities respond?

“The data provided by MTG and Metop-SG will also support improvements in forecasting in general. The better we characterise the initial conditions, the more robust our computer simulations become, and the better we will be able to predict how things will develop in the future.

“People, businesses and authorities can use this information to plan, schedule, and lead better lives; everyone makes use of these meteorological reports in some way. All of the evidence we have seen so far suggests it is going to be great!”

The much-anticipated launches of MTG and Metop-SG satellites seem a world away from Fourrié’s days as an EUMETSAT fellow in the early 2000s, when she helped to pioneer some of the first data assimilation algorithms for regional numerical prediction models ahead of the launch of Meteosat Second Generation satellites. 

“My fellowship was a great opportunity to develop the knowledge and skills needed to assimilate meteorological data, and also provided some wonderful exchanges with the EUMETSAT community that continue to this day,” she recalls. 

“There have been some amazing advancements in forecasting since then – and MTG and Metop-SG programmes will continue this revolution. It’s a very exciting time to be a meteorologist and, as a team leader, to train young scientists in an important and fast-moving field. It’s rewarding, fruitful, and gratifying for everyone in the team to exchange with experts far beyond meteorological services, and see how our work is contributing to improved weather forecasts and other critical endeavors.”

Author:

Adam Gristwood