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

Abstract

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 ( f o Es ), amplitudes of 2–32-day f o Es oscillations and filtered 16-day f o Es oscillations is conducted on the basis of f o Es measurement data for 1965–1989 from the world ionosonde network. Averaged monthly values of the zonal wind u ¯ 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 u ¯ index and the interpolated values of f o Es and 4–24-day f o Es 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 f o Es wave perturbation field in the Northern Hemisphere. A connection between the annual prevailing directions of 4–24-day f o Es 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 f o Es oscillation field.