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Plasma irregularities around 150-km altitude at centimetre scales with SYISR (Yue et al., 2024).

Plasma irregularities around 150-km altitude at centimetre scales with SYISR (Yue et al., 2024).

Published: 11 November 2025

ISSI International Team #571 report

by Fabio Crameri

Highlights

From the Teams

Space Weather

Mesosphere

Atmosphere

Connecting Earth and Space to Understand Day-to-Day Changes in the Upper Atmosphere

Between the air we breathe and the vastness of space lies one of the least understood parts of our planet’s atmosphere — the mesosphere and lower thermosphere (MLT). This region, roughly 50 to 120 kilometres above the Earth’s surface, might seem remote, but it plays a crucial role in shaping the environment that satellites, astronauts, and communication systems rely on.

ISSI International Team #571, co-led by Dr. Jorge L. Chau from the Leibniz Institute of Atmospheric Physics in Germany and Prof. Dr. Huixin Liu from Kyushu University, Japan, set out to unravel how this “gateway to space” behaves — and why it changes so much from one day to the next, especially at low latitudes near the equator.

A global effort to study an atmospheric frontier

The team brought together specialists in atmospheric dynamics, chemistry, and space physics to explore how different layers of the atmosphere talk to each other. Their collaborative work included one virtual kickoff meeting and two in-person workshops in Switzerland and China, fostering discussions that crossed both disciplines and continents.

At the heart of their mission were three key questions:

How can we measure and describe daily changes in the MLT at low latitudes?
How do weather systems lower in the atmosphere influence these changes?
How do variations in the MLT affect the upper atmosphere and ionosphere and, in turn, our communication and navigation systems?

Highlights and discoveries

Over the project’s duration, the team examined several remarkable atmospheric events and processes, including:

An unusual westward wind event observed around the March equinox of 2023.
The MLT’s contrasting behaviour during strong and weak polar vortex conditions.
The formation of sporadic E layers — thin layers of ionisation that can disrupt radio waves.
The impact of solar storms, including the intense 2024 events, on the MLT and ionosphere.

Data visualisation showing vertical and horizontal structures of the extreme Easterly wind event in the March equinox in 2023 after Suclupe et al., 2024 and Sato et al., 2025.

Vertical and horizontal structures of the extreme Easterly wind event in the March equinox in 2023 (adapted from Sato et al., 2025).

Their collaboration has already yielded more than a dozen scientific papers. Among the highlights:

A study (Sato et al., 2025, Geophysical Research Letters) explained the rare March 2023 westward wind event using a new high-resolution reanalysis covering the entire middle atmosphere.
Innovative use of the Japanese JAWARA reanalysis dataset to improve understanding of MLT dynamics.
New insights from the Chinese Sanya Incoherent Scatter Radar (SYISR) — a state-of-the-art instrument capable of probing small-scale irregularities in the ionosphere and their link to atmospheric disturbances.

First detection of plasma irregularities around 150-km altitude at centimetre scales with SYISR (Yue et al., 2024).

First detection of plasma irregularities around 150-km altitude at centimetre scales with SYISR (Yue et al., 2024).

Together, these advances help explain how weather patterns in the troposphere and stratosphere ripple upward to influence space weather and satellite operations, and how processes in near-Earth space can, in turn, feed back into the atmosphere below.

Why it matters

Understanding the MLT and its day-to-day variability is more than an academic challenge. This region acts as a bridge between the Earth’s weather and space weather, meaning that what happens there can directly affect systems we rely on daily, from positioning by Global Navigation Satellite System (GNSS) to satellite communications.

By combining theory, observation, and models, Team #571 is helping to build a more complete picture of how the Earth and space are interconnected. Their work provides essential insights for predicting and mitigating the effects of space weather on our modern technological world.

For the team’s publication list and more details, go to: https://teams.issibern.ch/mlt-lola/

ISSI International Team #571 demonstrates how bringing together global expertise — from radar specialists in China and Europe to atmospheric modellers in Japan, Europe, and North America — can lead to new insights into the dynamic region that links our planet to space.

For more on ISSI’s International Teams Programme and its support for cross-disciplinary collaboration, visit https://www.issibern.ch/scientific-opportunities/international-teams/

A Spiral Amongst Thousands

Credits ESA/Webb, NASA & CSA, A. Martel