Study on the Detectability of Typhoon-Generated Acoustic-Gravity Waves

In this paper, the detectability of the ionospheric response to the typhoon-generated acoustic-gravity waves was studied through the statistical analysis of the HF Doppler shift records which come from the corresponding observation station at Peking University （39.4°N, 116.2°E） and a comparison with corresponding typhoon data. It is shown that the HF Doppler frequency sounding can be an effective tool for detecting the acoustic-gravity waves excited by typhoon, and the detectability is as high as up to 22 out of 24 for the present study. The detailed analysis of the HF Doppler records at different stages of the typhoon influenced period was made under the quiet conditions. Then, a comparison was made with the results of Huang （2 out of 12） and the possible causes of the differences between these two studies were analyzed. The non-linear propagation process of the main disturbances is reappeared by the method of numerical simulation, and the simulation results are in good agreement with observation results and the linear theory of acoustic-gravity waves propagated in the atmosphere. This confirmed that the detectability should be high in general. Also it is shown that the differences of detectability may be due to the fact that the detectability keeps a close correlation with the difference of relative locations of the source of typhoon and Doppler observation sites, and the propagation pattern of the medium-scale TIDs in the ionosphere.