Rossby waves sources over the Eastern Northern Pacific and their impact on the global atmosphere from a set of CMIP6 large ensembles

The Rossby Wave Sources (RWS), RWS trigger wave-like patterns arising from the upper troposphere of the north-eastern Pacific region, causing a response around the Northern Hemisphere with alternating regions of positive and negative correlation values between RWS and geopotential height at 500 hPa (Z500). Increased RWS intensity during summer is related to negative temperature anomalies over western North America, and positive
temperature anomalies over eastern North America, concurrently with increased precipitation over the western subtropical Atlantic and Northern Europe during summer. Colder than normal conditions in the North Pacific Ocean intensify the RWS and its impact on the global atmospheric circulation. We use 7 CMIP6 large ensembles for the period 1950-2014 to analyse how they reproduce the response in the global atmosphere to RWS over the North-eastern Pacific Ocean. The waveguides that RWS produce from the North-eastern Pacific around the globe show that CMIP6 large ensembles have displaced crests and troughs from the North-eastern Pacific compared to the locations of ERA5, although all of them show the spread of the signal worldwide.
This location displacement of crests and troughs relies on how intense compared to ERA5 is the bias of the modelled westerly subpolar jet stream intensity reaching Europe from the North American continent. Models with a stronger bias in intensity show that the negative RWS-Z500 correlations over Scandinavia are weakened. Correspondingly, the same applies to the south-to-north component of the bias at 200 hPa. As in ERA5, the CMIP6 large ensembles show that warmer than normal SST over the North Atlantic, constraint the teleconnection only to the North American continent.