Twenty-Seven-Day Zonal Wind Fluctuations in the Troposphere and Lower Stratosphere under the Influence of Solar Activity

Abstract

Longitudinal, latitudinal, and altitudinal features of the zonal wind in the Northern Hemisphere under the influence of 27-day variations of solar activity (SA) were studied. The research aims to improve the accuracy of weather forecasts and deepening our knowledge about dynamic processes of the interaction of atmospheric layers. Zonal wind data by 5° latitude from the website https://psn.noaa.gov at the longitudes of Europe and North America from 15 altitude levels (from 1000 to 10 hPa) and SA data from the website https://www-app3.gfz-potsdam.de were used. Twenty high-amplitude 27-day SA cycles during the decline phase of the 23rd 11-year solar cycle from 2002 to 2004 were studied. The average 27-day wind changes for each latitude and altitude are calculated by the superposed epoch analysis separately for the winter and summer seasons. For the first time, 27-day latitudinal and altitudinal variations of zonal wind with an amplitude of ~8 m/s, capable of influencing the weather in the extratropical atmosphere, were established. Despite the significant difference in the background wind field in winter and summer, the response of the wind field to SA influence is similar for both seasons. The maximum wind changes occur in the southern part of the polar atmospheric cell and the northern part of the Ferrell cell (50°–70° N) and gradually decrease in magnitude to the south and north. Wind changes are many times smaller in the tropical troposphere. At the boundaries of the global circulation cells, the direction of disturbed wind changes to the opposite. Changes in the position of jet streams by more than 1° in latitude and changes in the size of atmospheric circulation cells are also observed. In terms of height, the largest changes in the wind at all latitudes occur in the upper troposphere. There is a close relationship between the magnitude of the perturbed wind and changes in the tropopause height. The impact is realized through two-way dynamic stratospheric-tropospheric interaction, primarily in the area of the polar night jet and polar front jet stream. The presence of significant wind changes for the summer season indicates an important role not only of planetary-scale Rossby waves but also of shorter-wavelength waves. At the same time, their upward propagation can be ensured by nonlinear interaction between them.