General features of 4–24-day waves in sporadic E-layer variations and their connection with equatorial stratospheric QBO Original Research Article

This paper summarizes the results of our research in sporadic E-layer (Es) dynamics with planetary wave periods (2–32 days) in the Northern Hemisphere and its connection with equatorial stratospheric quasi-biennial oscillation (QBO). The interpolation of averaged daily values of Es highest frequency (image), amplitudes of 2–32-day image oscillations and filtered 16-day image oscillations is conducted on the basis of image measurement data for 1965–1989 from the world ionosonde network. Averaged monthly values of the zonal wind image in the equatorial stratosphere at the 19–31 km height interval are used as the index of quasi-biennial oscillation of atmospheric circulation. A correlation analysis between the annual averaged values of image index and the interpolated values of image and 4–24-day image oscillations showed significant correlation in the sector of longitude from 30° to 270° (to the East of Greenwich) and latitude from 15°N to 75°N. We have developed an original algorithm for detecting a spatial motion in scalar field of any interpolated geophysical parameter in a specific local area. The algorithm is used to obtain zonal and meridional projections of local displacement of the 4–24-day image wave perturbation field in the Northern Hemisphere. A connection between the annual prevailing directions of 4–24-day image wave perturbations and the QBO phase (eastern or western) of atmospheric circulation is revealed on the basis of correlation analysis. The strongest correlation is discovered in the area around 60° N, 120° E in the case of filtered 16-day foEs oscillation field.