The study of the impact of polar warming on global atmospheric circulation and mid-latitude baroclinic waves using a laboratory analog

The results of experimental and numerical modeling of Arctic warming in a laboratory dishpan configuration are presented. The Arctic warming is reproduced by varying the size of a local cooler in the "atmospheric" regime, in which the flow structure is similar to the general atmospheric circulation. The laboratory Arctic warming results in a relatively weak response of the meridional and zonal circulation except in the polar region, where the polar-cell analog becomes weaker, shifts closer to the middle radii, and is mainly located in the upper layer. The structure of analogs of Hadley and Ferrel cells is the same for all considered configurations. The decrease in the velocity of the zonal flow (analog of westerly wind) and the change in baroclinic wave activity at laboratory middle latitudes was less than 10 %. The most important result of this study is a noticeable transformation of the mean temperature field. Namely, the central region and most of the lower layer become warmer, while most of the upper layer and the peripheral (equatorial) part of the lower layer become colder. The nature of this phenomenon is closely related to the changes in radial heat fluxes. The weakening and upward shift in the polar-cell analog caused by laboratory Arctic warming provides a significant reduction in the negative heat flux near the bottom. This inevitably leads to a temperature increase in the bottom layer. It is also shown that Ekman pumping due to non-slip boundary conditions at the surface of the cooler has a strong influence on the structure and intensity of the polar-cell analog.