Balloons on a Climate Mission: Searching for Clues in the Stratosphere

5 June 2025

The launch of the weather balloon on 27 May was the first of many this year – marking the start of a unique measurement campaign which will continue until October, with weekly launches. Its aims include investigating the influence of the Asian summer monsoon on the stratosphere over Europe across an entire season.

During the balloon campaign, several miniature sensor packages will rise to an altitude of over 30 kilometers, directly recording the vertical distribution of various trace gases, aerosols, and cloud particles. These precise measurements will also help verify measurements from satellite instruments and check the results of climate models.

The balloons carry a range of different measuring instruments. Some transmit their data directly to the climate researchers' ground station. Others take air samples in the troposphere, which are then examined later in the laboratories of the Institute of Climate and Energy Systems (ICE-4). "As a result of the decreasing air pressure, the balloon expands more and more at higher altitudes until it finally bursts. The devices are tracked and can then be recovered after they land," explains atmospheric researcher Christian Rolf, who is coordinating the campaign.

Long-term effects on the climate

The balloon campaign follows on from the PHILEAS aircraft campaign in 2023. This campaign also focused on the climate impact of the Asian monsoon. In this large-scale weather system, thunderstorms accumulate and transport heavily polluted air from the lower atmosphere in Southeast Asia up to an altitude of 15 kilometers. From there, the polluted air spreads westward to the eastern Mediterranean and eastward across the Pacific Ocean.

The monsoon has no direct influence on the weather in Europe. It is the long-term effects on the climate that are at stake here. “The Asian monsoon region is characterized by strong vertical transport,” explains Christian Rolf. "Air masses near the ground, containing all the local emissions, are thus quickly transported vertically to the tropopause. From there, the air masses slowly spread across the entire northern lower stratosphere, so that we can also measure the influence and air from the Asian monsoon here."

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Further Information

Report on the ICE-4 website

Major balloon campaign at ICE-4 has started

The weather balloon launch on 27th May 2025 was the first of many this year. This unprecedented campaign effort, which will continue with weekly launches until October, is going to explore, among other goals, the influence of the Asian Summer Monsoon on the stratosphere above Europe across more than an entire season.

Press release 12 October 2023

PHILEAS campaign successfully completed

HALO research aircraft has provided valuable contributions to research into the effects on the climate of the Asian Summer Monsoon and the wildfires in Canada