A Warming Climate's Wandering Jet: Investigating Jet Stream Waviness with Hemispheric and Regional Lenses

In the context of a warming Arctic, the behavior of jet streams, as they increasingly meander, is becoming more intricate and variable. In this study, we analyzed approximately 50 models, in total, from the CMIP6 project and ERA5 reanalysis to quantify jet stream waviness and its response to climate change. We found varying trends and spatiotemporally dependent significance levels in jet stream meandering, particularly in the Northern Hemisphere, linked to rising CO₂ levels and natural climatic variability.

Building on this foundation, our research delved into the complex patterns of jet stream meandering. We analyzed The Diagnostic Evaluation and Characterization of Klima (DECK) experiments within the CMIP6 framework—AMIP, piControl, and a scenario with a 1% per year CO₂ concentration increase—including 21, 18, and 13 models, respectively. These specific datasets and models provided a robust foundation for unraveling the climatic factors affecting the jet stream's trajectory and variations. Spanning from 1979 to 2014, our analysis uses daily geopotential height readings to quantify jet stream waviness and assess the impact of climate change.

The analysis centers on normalizing arc lengths to measure jet stream waviness using the meandering index (M-Index). Additionally, the study investigates median and minimum waviness in Eurasia, the North Atlantic, North America, and the North Pacific to explore regional effects. These insights reveal significant seasonal variations and trends in jet stream behavior, crucial for understanding the impact of climate change on atmospheric dynamics.

In conclusion, this study aligns with the IPCC AR6, thoroughly investigating the complex nature of jet stream meandering and illuminating the roles of CO₂ and natural variability. By adhering to the diverse metrics outlined by the IPCC, our research methodically quantifies jet stream trends with the help of M-Index calculations. This thorough exploration dissects the complex interplay between global warming and atmospheric behavior, demonstrating the depth and analytical rigor that is characteristic of climate research aligned with IPCC standards.