Catching the Sun


Get to know Jean-Marcel Rivonirina, a winner of the 2022 EUMETSAT Early Career Scientist Award

Jean-Marcel Rivoniriva, a winner of the 2022 EUMETSAT Early Career Scientist award, wants to better characterise cloud variability and understand their effects on UV radiation, using data provided by EUMETSAT’s Meteosat geostationary satellites.

Last Updated

01 November 2023

Published on

15 September 2023

As anyone who has been sunburnt on an overcast day can attest, clouds can be far from perfect in blocking out harmful ultraviolet (UV) rays. And, under certain conditions, cloud cover can even increase UV levels on the ground, a paradox that Jean-Marcel Rivonirina wants to better characterise in the South Indian Ocean region, supported by data from EUMETSAT’s Meteosat mission.

“Cloud types such as high-altitude cirrus and broken clouds can, in some circumstances, scatter UV rays in ways that can temporarily raise UV levels on the ground far higher than we would expect to see even under clear skies,” explains Rivonirina, who is a PhD student at the Institute and Observatory of Geophysics of Antananarivo at the University of Antananarivo, Madagascar, and the University of La Réunion’s Laboratoire de l'Atmosphère et des Cyclones.

“This can be very hazardous, especially when people do not recognise the danger or protect themselves from the Sun.”

Jean-Marcel Rivonirina

Jean-Marcel Rivonirina studied physics during his undergraduate studies, and then pursued a meteorology doctorate after learning about the potential impacts the field can make on lives and livelihoods. As a winner of the 2022 EUMETSAT Early Career Scientist Award, Rivonirina is a guest of honour at this year’s EUMETSAT Meteorological Satellite Conference in Malmö, Sweden. “Winning the EUMETSAT Early Career Scientist prize is an honour for me and my university. It recognises the crucial role Meteosat data has for countries in and around the Indian Ocean. I am very much looking forward to taking part in the conference in Sweden, and want to thank EUMETSAT for this incredible opportunity,” he added.  

Photo courtesy of Jean-Marcel Rivonirina.

Keeping pace

Because clouds are very dynamic in nature, predicting these conditions is very challenging.

“The aim of our research is to better characterise cloud variability and understand their effects on UV radiation over the Indian Ocean, where very few studies have been carried out to date,” Rivonirina explains.

“In order to do this, we need to gather as much information about the current state of the atmosphere as possible, including characteristics like cloud type and cloud fraction – the percentage of the sky that is covered by clouds at a specific location and time.

“We use two complementary techniques: one using satellite data provided by geostationary satellites such as Meteosat, which has excellent spatial coverage and provides observations every 15 minutes. Another is ground-based cameras in permanent observatories, which have a good resolution but low spatial coverage.”

Combining data from camera and satellite sensors of vastly differing spatial dimensions is a big challenge, requiring the use of specially developed algorithms that can help present data in a way that enables specialists to track the distribution, movement, and properties of clouds.

“Bringing these datasets together not only enhances the amount of data available on cloud cover, it also enables us to corroborate independent observations, improving their accuracy,” Rivonirina adds.

“It’s become a huge passion of mine to work in this area: our research will hopefully improve short- and medium-term weather forecasts over the Indian Ocean, and over time also contribute to studies of climate change.”


Adam Gristwood