Stratosphere–troposphere coupling during extreme weather change in Alaska in January–February 1989: case study

We analyze extreme cold and warm weather events in Alaska during January–February 1989, first described in 1990. Unlike previous studies focused on tropospheric processes, we compare contrasting surface temperatures, including stratospheric variability. Total ozone, zonal and meridional winds, vertical velocity, sea level pressure, potential vorticity, and tropopause pressure are considered based on reanalysis data and observed temperature. Relationships between abrupt surface temperature changes and atmospheric variables were established based on changes in their geographic and vertical distributions and linear correlation estimates. On the coldest day, 25 January (–43°C at Barrow, northernmost Alaska), an anomalous increase in total ozone over Alaska, accompanied by stratospheric warming, transformation of the vertical temperature profile, and deep tropopause fold, was associated with the formation of a temperature minimum of –40°C to –50°C in the polar troposphere. That suggests that areas with extremely high total ozone may be associated with strong surface cooling in the polar regions. The lack of a significant sea level pressure anomaly and weak surface winds in Barrow imply a relatively smaller tropospheric contribution to the severe cooling compared to the stratosphere and the tropopause. The anomalous warming in Barrow on 6 January (–8°C) and 4 February (–3°C) occurred due to the advection of warm air by southerly flows associated with distant cyclonic and anticyclonic circulation systems. Among the parameters analyzed, surface temperature at Barrow was strongly anticorrelated with total ozone ( r = –0.74) and positively correlated with surface v -wind ( r = 0.61), highlighting the important role of the stratosphere and surface meridional wind in local weather variation during this period.