Asymmetry in the response of central Eurasian winter temperature to AMO

Abstract

The asymmetry in the teleconnection of the central Eurasian winter surface air temperature (SAT) with the Atlantic multidecadal oscillation (AMO) is discussed using observations and model simulations. Observations indicate that the winter SAT over central Eurasia (30°–70°E, 30°–50°N) shows significant positive anomalies during the warm AMO period but weak and insignificant anomalies in the cold AMO period. In general, the warm winters in central Eurasia are associated with large-scale negative sea level pressure anomalies in Europe, anomalous southwesterly winds at 850 hPa over Europe, the “+ − +” geopotential height anomalies at 500 hPa in the south of Greenland, northern Europe, western Asia, and the slant north–south “+ −” pattern jet stream anomalies at 200 hPa in the north and south of the Caspian Sea. Reverse patterns occur during cold winters. These statistically significant features are observed in the warm phase of AMO. Reversed circulation anomalies are observed during the cold phase of AMO; however, these anomalies are weak and not statistically significant. Furthermore, the asymmetry in the atmospheric response to AMO is well supported by simulations with a suite of GFDL atmospheric model idealized experiments and four CMIP5 models historical experiments. Both observations and simulations indicate that Rossby waves propagating from the North Atlantic eastward to Eurasia emerge in the warm AMO and disappear in the cold AMO. Thus, the different propagations of Rossby waves, induced by the different surface thermal conditions of the warm and cold AMO, are the potential connection between the North Atlantic Ocean and central Eurasian climate, and may explain the asymmetry.