The subtropical westerly jet is a high-altitude, fast-moving air current that flows from west to east in the subtropical region of the Earth's atmosphere. It's an important part of the atmospheric circulation that influences weather patterns and climate conditions worldwide. Scientists have noticed that this jet has been shifting northward as a result of global warming. They've been trying to figure out why, focusing on two main factors: changes caused by temperature and those driven by swirling air patterns called eddies. But it's been hard to say which factor is more important. A new study by the Institute of Atmospheric Physics of the Chinese Academy of Sciences may have some answers. Researchers looked at data from the past 40 years and found that during winter in the Northern Hemisphere, temperature changes seem to be the main reason for the jet's shift north. They think this happens because changes in temperature structure are the fundamental rule governing how air moves around the globe.
They suggested that about 72% of the jet's northward movement is due to changes in temperature, while about 28% is due to swirling air patterns.
"In the context of climate change, the northward shift of the zonal-mean subtropical westerly jet in the boreal winter results from the interplay of multiple mechanisms, but pinpointing the primary controlling factors is essential for refining our research thought," said Dr. SHENG Chen, lead author of the study published in Journal of Geophysical Research-Atmospheres, "Our research suggests that changes in how heat moves in the atmosphere are a big part of it." This study builds on the team's previous research within the Potential Vorticity Circulation framework, which examines how air movements affect weather patterns. The new findings suggest that the northward shift of the subtropical westerly jet likely indicates changes in how different parts of the Northern Hemisphere interact with each other in terms of air circulation and weather systems. Fast-moving air current with swirling air patterns called eddies (Image by SHENG Chen)
