Head in the clouds: how to understand weather better

The weather couldn’t be worse. Nothing but a sea of grey. Not a trace of the Aletsch Glacier. Instead of a glorious alpine panorama, today all the Jungfraujoch can offer its guests are thick clouds. But that hasn’t deterred a handful of tourists from venturing onto the Sphinx observation terrace. The wind is lashing against their faces, and snowflakes are swirling through the air. It is bitterly cold. The visitors from all over the world just about manage to muster a brave smile for the camera. Two storeys further up – and inside, where it’s warm – Ulrike Lohmann and Larissa Lacher are gazing through the window at the clouds and they’re tickled pink. But this is no schadenfreude, it’s the enthusiasm typical of scientists who have a burning passion for their subject.

Lohmann is an atmospheric physicist and a professor at the Institute for Atmospheric and Climate Science at ETH Zurich. She is visiting Lacher, her doctoral student, at the High Altitude Research Station Jungfraujoch. This young scientist is spending four weeks here at the Sphinx Observatory, 3,571 metres above sea level, in order to make climate measurements. She is interested in particles in the air that aid cloud formation. And if today’s weather is anything to go by, they are hardly in short supply up on the mountain.

Desert sand meets glacial ice

The blanket of clouds briefly opens to offer a glimpse of the snow fields outside the window. It’s not much, but enough for Lacher to be able to show her boss the reddish deposits in the snow. The two women dart from one window to the next before the clouds swallow everything up again. What has set the researchers’ pulses racing looks just like dirty snow to visitors from the city. But it’s actually dust from the Sahara. It comes from the last Sahara dust event, which carried sand northwards from Africa in May. The two scientists are interested in how the Saharan sand affects the formation of clouds on the Jungfraujoch. Because fine particles like Saharan dust in the air – known as aerosols – act as condensation nuclei upon which water or ice can accumulate, depending on the temperature and relative humidity. This is how cloud droplets or ice crystals are formed, which eventually combine to make entire clouds. These “warm clouds” mostly consist of relatively small water droplets and are recognisable from their sharp outlines. Ice clouds, on the other hand, are composed of ice crystals that fall out of the cloud more readily on account of their size, which is why they typically have blurred outlines.

Lacher completed her Master’s thesis in Lohmann’s lab, and back then she was already studying Sahara dust events and their impact on the formation of clouds. She did this on Tenerife in the Canary Islands, which lies only 250 kilometres from the Sahara Desert. “Measuring the same Sahara dust event during two parallel measuring campaigns – initially in Tenerife and now here on the Jungfraujoch – that would be a great success”, says Lacher, and her blue eyes light up. Because this would enable her to study the ageing process of the aerosol particles and their influence on the formation of clouds.

Published in collaboration with ETH Zurich

Author: Corinne Hodel is a biologist for the Institute of Zoology at the University of Zurich.

Image: Tropical Cyclone Ian is seen in this NOAA GOES satellite handout image taken at 14:00 GMT January 12, 2014. REUTERS/NOAA/Handout via Reuters.