Screening Caribbean clouds from top to bottom

Clouds reflect the sun’s rays and thus have a cooling effect. But they also retain warmth like a blanket. Scientists are not yet able to say what their net effect is on climate change. It’s even called ‘one of the greatest mysteries’. Delft researchers are trying to help unravel this mystery.

Cloud researcher Dr Louise Nuijens and PhD Students Geiske de Groot and Kevin Helfer at the department of Geoscience & Remote Sensing (CEG Faculty) are taking part in a large-scale project called EUREC4A (Elucidating the role of clouds-circulation coupling in climate) in Barbados. Some 40 institutions from 10 countries are involved in this German-French initiative.

“The choice of the island of Barbados is not coincidental,” says Nuijens. “Barbados’ easterly position in the Caribbean makes it ideal. The clouds, low cumulus that are part of the eastern trade winds, are still pure. They are not affected by mountain ranges or industry, and low cumulus clouds, the ones we are most interested in, are most abundant in the sub-tropics.”

Measuring the size of droplets

The Caribbean clouds will be screened from top to bottom. The scientists will study the dynamics of the atmospheric and oceanic conditions in which the clouds form and dissolve. Four ships will observe clouds from below, five planes will dive into them. Kites with measuring instruments will be launched and probes will be dropped from the air. Satellites and radars will register data from a distance.

Lidar instruments shoot beams of laser light into the atmosphere

The TU Delft scientists will use Lidar technology on the German research vessel Meteor. Lidar instruments shoot beams of laser light into the atmosphere to measure the movement of air around the clouds. Lidar will also enable the scientists to measure the water vapour around the clouds. Water vapour has a significant impact on the way in which clouds grow and behave. Research at Eurec 4a began on 20 January and will run until 20 February.

More accurate

The findings can be incorporated into climate models to make them more accurate. Clouds are already appearing in the most recent models which the international climate panel IPCC will soon be examining.

EUREC4A is the first field study to test hypothesized mechanisms whereby changes in cloudiness with global warming act to amplify this warming, a positive feedback which would increase Earth’s climate sensitivity. These hypotheses have been distilled from several rounds of international climate model intercomparison studies, over a period of decades.