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Tapio Schneider, Tobias Bischoff, and Hanna Płotka, 2015: Physics of Changes in Synoptic Midlatitude Temperature Variability. J. Climate, 28, 2312–2331.

doi: http://dx.doi.org/10.1175/JCLI-D-14-00632.1

Physics of Changes in Synoptic Midlatitude Temperature Variability

Tapio Schneider and Tobias Bischoff

ETH Zurich, Zurich, Switzerland, and California Institute of Technology, Pasadena, California

Hanna Płotka

ETH Zurich, Zurich, Switzerland


This paper examines the physical processes controlling how synoptic midlatitude temperature variability near the surface changes with climate. Because synoptic temperature variability is primarily generated by advection, it can be related to mean potential temperature gradients and mixing lengths near the surface. Scaling arguments show that the reduction of meridional potential temperature gradients that accompanies polar amplification of global warming leads to a reduction of the synoptic temperature variance near the surface. This is confirmed in simulations of a wide range of climates with an idealized GCM. In comprehensive climate simulations (CMIP5), Arctic amplification of global warming similarly entails a large-scale reduction of the near-surface temperature variance in Northern Hemisphere midlatitudes, especially in winter. The probability density functions of synoptic near-surface temperature variations in midlatitudes are statistically indistinguishable from Gaussian, both in reanalysis data and in a range of climates simulated with idealized and comprehensive GCMs. This indicates that changes in mean values and variances suffice to account for changes even in extreme synoptic temperature variations. Taken together, the results indicate that Arctic amplification of global warming leads to even less frequent cold outbreaks in Northern Hemisphere winter than a shift toward a warmer mean climate implies by itself.

Keywords: Atmospheric circulation, Synoptic climatology, Anthropogenic effects, Climate change, Climate variability

Received: September 11, 2014; Final Form: December 2, 2014

Corresponding author address: Tapio Schneider, ETH Zurich, Sonneggstr. 5, 8092 Zurich, Switzerland. E-mail: tapio@ethz.ch

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