Simulating the extreme 2013/2014 winter in a future climate

How would the spell of extreme weather observed over North America and western Europeduring the 2013/2014 winter manifest itself in a warmer climate? Here a forced sensitivity method isused to calculate optimal model tendency perturbations which result in a simulation which has its upperatmospheric circulation shifted in the direction of the January 2014 jet stream pattern. When applied toa simulation run under present-day conditions the main features of the observations of this event arereproduced, such as the more zonal position and increased strength of the midlatitude North Atlantic stormtrack, the anomalous temperature pattern over North America, and the excessive precipitation in parts ofEurope. When this method is applied to a future warmer climate, the North Atlantic storm track changesto a more zonal orientation, but its strength does not see the significant increase that is obtained in thepresent-day simulations. Despite southward advection of polar air into northeastern America, which hasalso occurred during the 2013/2014 winter, the associated drop in temperature is less in the future climatecompared to the present-day climate because of Arctic amplification. The less steep drop in temperaturesover northeastern America leads to a smaller land-sea temperature contrast, less baroclinic instability, anda reduced increase of midlatitude storminess. While one may expect the future increased atmosphericmoisture content to augment the net precipitation, for this specific event, this effect is counterbalanced bythe dynamics, leading to a similar net increase in precipitation in the future simulations compared to thepresent day

Rasmijn, L. M., van der Schrier, G., Barkmeijer, J., Sterl, A., & Hazeleger, W. (2016). Simulating the extreme 2013/2014 winter in a future climate: SIMULATING THE EXTREME 2013/2014 WINTER. Journal of Geophysical Research: Atmospheres, 121(10), 5680–5698.

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