Department of Geophysics The regional characteristics of couplings between ionosphere and lower atmosphere through gravity waves Prof. Z. Xiao Department of Geophysics Peking University Beijing, 100871 China

For discussions We have evidences of the responses of the ionosphere to typhoons. The response does show certain special common features Two stations in China (Changchun and Wulumuqi) with the same latitude but about 40 degree difference in longitude showed very different occurrence frequencies of spread-F. Changchun is near the east coast of the Country while wulumuqi deep in the Chinese mainland. the occurrence of spread-F seems to be influenced by surface meteorology factors (waves in the lower atmosphere as seeds and others?) It seems that gravity waves in the lower atmosphere not only cause the TIDs in the ionosphere (this is well known), but also influence the morphological features of ionosphere so the ionosphere should have certain regional characteristcs

Left-upper: record of ionosphere Doppler shift during a typhoon Left-upper: record of ionosphere Doppler shift during a typhoon. The typhoon landed on mainland around 16h(LT). Notice the period evolution and spread-F during the night left-lower: another typhoon which were near the mainland and became strongest around the night of 21st and not far from the mainland right-lower: comparison of the occurrence of spread-F at Changchun and Wulumuqi for all seasons. Noticd that spread-F occurred much more frequent at Changchun