The 2015/16 Northern Hemisphere winter season was marked bypeculiarities in the circulation pattern in the high-latitude mesopauseregion. Wind measurements from the Andenes (69° N, 13° E)meteor radar show westward winds below 84 km and eastward winds above. Thiswind pattern in the zonal wind was observable between the end ofDecember 2015 and the end of January 2016, i.e., conditions that are typicalfor the summer were found during winter. Additional meteor radar measurementsat midlatitude stations did not show such a zonal wind reversal butindicate, together with the polar latitude stations, a reversal of thehorizontal temperature gradient. This is confirmed by global satellitemeasurements. Therefore, it is plausible that the polar latitude summer-likezonal wind reversal in December–January is in accordance with the reversedhorizontal temperature gradient assuming a thermal wind balance between mid-and polar latitudes. The reversed horizontal temperature gradient itself isinduced by stationary planetary waves at lower and midlatitudes in themesosphere, leading to a weakening of the residual circulation above theEuropean sector.
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