Rapid Arctic warming and its link to the waviness and strength of the westerly jet stream over West Asia

Abstract

Rapid sea-ice loss and warming of the Arctic within the past few decades have contributed to changes in the strength and location of midlatitude jet streams. Using ERA-Interim data for the period 1979–2018, warming of the Arctic compared to midlatitudes and its impact on the waviness and strength of the westerly jet stream over West Asia are investigated. Pre- and post-Arctic amplification periods are defined as 1979–1993 and 2004–2018, respectively. Near-surface temperature variability is decreased in the Arctic in the post-Arctic amplification period when a larger area of open ocean has been exposed to the atmosphere. In both pre- and post-Arctic amplification periods, near-surface temperature variabilities in spring and summer were less than half as much of its variability in winter. During the period 1979–2018, both the Arctic and West Asia have warmed, with much higher warming of the Arctic in autumn and winter. Indeed, in contrast to the continental cooling pattern observed in parts of North and Northeast Asia, West Asia has warmed in recent decades. Following a decrease in the meridional temperature gradient, the upper-tropospheric jet stream over West Asia has been reduced in the post-Arctic amplification period in all seasons except autumn. In the post-Arctic amplification period, the zonal wind shear has been also reduced over West Asia in all seasons, while waviness of the Z500 isopleth has been increased in winter. A higher meridional mid-tropospheric waviness is found over the study region (20–75°E) in summer compared to winter because in summer the western part of this region is influenced by a strong subtropical high pressure, while its eastern part is influenced by the Indian monsoon and associated trough of low pressure. • Near-surface temperature variability is decreased in the Arctic in the post-Arctic amplification period • In contrast to cooling of some midlatitude regions, West Asia has warmed in recent decades • Upper-tropospheric jet stream over West Asia has been reduced in the post-Arctic amplification period • Zonal wind shear has been reduced over West Asia in all seasons, but waviness of Z500 isopleth has been increased in winter