THE WINTER ANOMALY OF RADIO WAVE ABSORPTION IN THE D-REGION AND THE PLANETARY WAVE IN THE STRATOSPHERE

Abstract

Interrelations between stratospheric conditions and the strong absorption of radio waves in the D-region are investigated by using the daily data of the northern hemispheric maps of 10- and 30-mb, and of the ionospheric /min from December 1965 to March 1966. Analyses are based upon the time-longitudinal sections along 60'N circle of temperature and planetary wave in the stratosphere, and of the Jfmrn which is the deviation from the monthly median value, and the positive value of which represents stronger absorption than the normal, on every day at each station. Both the warmer region in the middle stratosphere and the stronger absorptive region in the D-region have a similar horizontal scale of the order of 1000 to 10000 km. It may be mentioned that the occurrence of unusual warming in the middle stratosphere is a sufficient condition for that of an absorption anomaly in the D-region, but not a necessary condition. On the relation between the transient part of the planetary wave at 10-mb surface and stronger absorption, both amplitudes reach nearly simultaneously a maximum in mid-winter for wave number one. Also, the movements of both phases are similar, in speed and direction, during Dec. 1965~middle Feb. 1966 for wave numbers one and two. These results suggest the important role of planetary waves in contributing to the absorption anomaly in the D-region.