In a landmark achievement poised to advance our understanding of extreme weather phenomena, Associate Professor Koji Iwano and his dedicated research team at Okayama University of Science have been honored with the prestigious 2025 MEXT Award for Science and Technology in the Research Category. This recognition by Japan’s Ministry of Education, Culture, Sports, Science and Technology underscores the team’s pioneering contributions to the measurement of air-sea momentum, heat, and carbon dioxide (CO₂) transfers specifically under the volatile and extreme conditions characteristic of typhoons. Their groundbreaking research promises to significantly enhance the precision of typhoon intensity forecasts and refine models related to climate change, factors critically important for disaster mitigation and environmental policy.
Central to this research is an innovative approach to studying the air-sea interface under typhoon conditions, a domain historically marked by scientific challenges due to the turbulent and complex nature of the interactions. The team has succeeded in creating realistic simulations that replicate how momentum and energy transfer between ocean and atmosphere during severe tropical cyclones, filling a critical gap in the understanding of atmospheric-oceanic coupling. Their results elucidate for the first time the intricate mechanistic relationships governing the transfer of heat, momentum, and CO₂ at the air-sea boundary as influenced by varying wind speeds and dynamic wave patterns encountered in powerful storms.
This study, titled “Investigation of Momentum, Heat, and CO₂ Transport Mechanisms at the Air-Sea Interface Under Typhoon Conditions,” was conducted through a collaborative effort involving Professor Naohisa Takagaki from the Graduate School of Engineering at the University of Hyogo and Professor Emeritus Satoru Komori from Kyoto University. Together, they have exploited interdisciplinary insights from fluid mechanics, atmospheric sciences, and environmental physics to push the frontier of experimental meteorology. Their holistic approach combines both theoretical analyses and real-world simulation platforms, creating an unprecedented experimental framework.
One of the most remarkable aspects of their research is the construction and utilization of Japan’s only large-scale indoor typhoon simulation tank. This unique facility can generate airflow over water surfaces at speeds reaching up to 70 meters per second — velocities akin to those seen in the eye wall of a severe typhoon. By replicating wave-breaking ocean surfaces and extreme wind stresses within a controlled laboratory environment, the research team overcomes the limitations and risks inherent in in-situ field measurements during typhoons. This controlled setting enables meticulous observation and quantification of momentum flux, thermal exchange, and gas transfer phenomena that were previously unattainable.
Their experiments reveal a fascinating nonlinear behavior in the transfer coefficients as wind speeds cross certain thresholds. Specifically, momentum transfer coefficients increase steadily with wind speed up to about 30 m/s, beyond which they plateau, contrary to prior assumptions of continuous growth. This saturation suggests a shift in the physical regime governing frictional forces between the air and sea surface. Conversely, heat transfer coefficients, which remain nearly constant at lower wind speeds, exhibit a marked acceleration above this 30 m/s threshold, indicating a decoupling of heat and momentum flux dynamics under extreme conditions. This nuanced understanding sheds light on how air-sea heat exchange intensifies during the strongest storm phases, likely impacting storm intensification processes.
Beyond momentum and heat, the team’s measurements also cover the transfer of CO₂, a greenhouse gas intricately involved in climate regulation. Precise quantification of CO₂ exchange during typhoons is vital to global carbon cycle models because these intense storms facilitate rapid and complex interactions between oceanic carbon reservoirs and the atmosphere. The indoor tank experiments demonstrate that extreme winds modulate the solubility and diffusivity of dissolved gases, highlighting the dual role of typhoons in both atmospheric dynamics and oceanic biogeochemical cycles.
Associate Professor Iwano emphasizes the critical need for these refined measurements to advance coupled atmosphere-ocean modeling systems. Current global models often fail to accurately resolve air-sea exchanges under the highest wind speeds, contributing to uncertainties in predicting typhoon tracks and intensities. By integrating the newly derived transfer coefficients and mechanistic insights from their experiments, meteorological models can approach a new level of fidelity. Improved modeling translates directly into better disaster preparedness and response strategies, potentially saving lives and reducing economic impacts.
The research also opens intriguing avenues for innovative typhoon mitigation strategies. By understanding the physics of air-sea interactions at fine resolution, the prospect emerges to explore artificial interventions on ocean surfaces, such as modifying wave patterns or altering surface roughness, to influence storm development. While these concepts remain speculative, the foundational work conducted by Iwano and colleagues lays the necessary groundwork for future applied meteorological engineering.
Reflecting on the significance of receiving the MEXT Award, Associate Professor Iwano articulates profound gratitude. He recognizes the rarity of large-scale experimental setups in modern science, where computational simulations often predominate. This accolade validates the enduring importance of empirical, high-precision laboratory experiments in elucidating complex environmental systems. With continued support, the team is committed to expanding this research program, fostering young scientists, and addressing pressing questions at the intersection of atmospheric physics and climate science.
In summary, the 2025 MEXT Award bestowed upon Associate Professor Koji Iwano and his collaborators signifies a milestone in atmospheric and oceanic science. Their successful employment of a large-scale indoor typhoon simulator to quantify momentum, heat, and CO₂ exchange under extreme wind conditions marks a major step forward in comprehending the air-sea coupling that drives typhoon dynamics. Their findings refine fundamental scientific knowledge, enhance predictive capabilities for some of nature’s most destructive forces, and open pathways for innovative environmental interventions with broad societal impact.
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Article Title: Investigation of Momentum, Heat, and CO₂ Transport Mechanisms at the Air-Sea Interface Under Typhoon Conditions
News Publication Date: April 15, 2025
Image Credits: Okayama University of Science
Keywords: Air-sea interaction, typhoon intensity, momentum transfer, heat transfer, CO₂ exchange, indoor typhoon simulation tank, extreme wind conditions, climate modeling, coupled atmosphere-ocean models, fluid dynamics, environmental physics
