A Thermal Wind Perspective of Driving Changes in Jet Stream Patterns

Abstract

It is evident that the jet streams are becoming more erratic and unstable in a changing climate. We investigate changes both in position and speed of the midlatitude jet streams at 300 hPa in  31 Atmospheric Model Intercomparison Project (AMIP) runs and the ERA5 reanalysis dataset investigating the ability of the thermal wind concept to explain changes in place and the regime of the jet streams, which are disturbed by Arctic amplification, is the core of this work. All data covers the period 1979-2014.  It is revealed that the changes in jet stream magnitude and position in the multi-model mean (MMM) can largely be explained by the thermal wind. We also discovered that the AMIP models reproduce trends in jet position and strength seen in  ERA5. Yet it is a must to state that when inspecting individual models, we find that some models can reproduce ERA5 trends in NH. The large variance in modelled trends, however, leads to a poorly represented MMM. In the end, the jet stream plays a significant role in shaping global weather patterns and is affected by changing climate as becoming more wobbly and unstable. The potential impact of Arctic warming on the jet stream and how it may lead to more extreme weather events in the mid-latitudes is taken under inspection from the window of thermal wind concept with this study.