Researchers at Kyushu University have made an intriguing discovery about the turbulence in the thermosphere – it shares the same physical laws as the wind in the lower atmosphere. Moreover, the wind in the thermosphere predominantly follows a cyclonic pattern, rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
These findings unveil a groundbreaking unified principle for the Earth’s diverse environmental systems and hold the potential to enhance the accuracy of both Earth and space weather forecasts.
At some point, we’ve all tuned in to catch the latest weather forecast, but the intricate research behind understanding how Earth’s air moves is undeniably complex.
“At the fundamental level, we study the interplay of kinetic energy in the atmosphere at different sizes and scales; that energy is mostly in the form of wind and turbulence. Over the decades, a massive amount of data has given us insight into how this energy flows and dissipates to affect the weather in the troposphere, the lowest layer of the atmosphere,” explains Professor Huixin Liu of Kyushu University’s Faculty of Science, who led the study. “My research focuses on the movements in the upper atmosphere, specifically the thermosphere, where we explore the corresponding laws governing the dynamics and energy flow in the region.”
The thermosphere, situated approximately 80-550 km above sea level, serves as the gateway to space and plays a significant role in space operations. Housing the International Space Station and numerous satellites, this critical region is also responsible for the creation of beautiful auroras.
In a collaborative effort, Liu partnered with meteorology researcher Dr. Facundo L. Poblet from the Leibniz Institute of Atmospheric Physics at the University of Rostock. Dr. Poblet’s expertise lies in studying the dynamics and turbulence in the lower atmosphere, specifically below the altitude of 100 km.
“My research is in space physics, and I wanted to see if we could apply his meteorological methods to my research domain,” explains Liu.
The team meticulously analyzed thermosphere wind data from two satellites: the Challenging Minisatellite Payload (CHAMP) and the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE). Utilizing this data, they calculated the third-order structure function of the wind, a statistical quantity that offers insights into the underlying turbulence. To their amazement, they made a groundbreaking discovery that the thermosphere exhibits a similar scaling law to that of the lower atmosphere.
“This means that both the thermosphere and the troposphere – despite having drastically different atmospheric compositions and dynamics – follow the same physical laws. How the energy flows and dissipates in these two regions are very similar,” continues Liu.
Despite significant progress in understanding the thermosphere, the intricate interplay of turbulence and waves at different scales has largely remained inscrutable. The team is delighted that their findings have illuminated this relatively unexplored aspect of near-space dynamics.
“Similar to atmospheric weather forecasting, comprehending the energy distributions in the thermosphere is vital to advance our understanding of space dynamics,” concludes Liu. “We hope these findings can be used to improve space weather forecasting and ensure the continued functionality and safety of satellite-based technologies essential to everyday life.”
Journal reference:
- Facundo L. Poblet, Huixin Liu, Jorge L. Chau. Third-Order Structure Functions of Zonal Winds in the Thermosphere Using CHAMP and GOCE Observations. Geophysical Research Letters, 2024; DOI: 10.1029/2024GL108367