资源环境科技发展态势分析平台

In this paper we present ionospheric disturbances during the simultaneous presence of two to three Large Meteorological Systems, classified as hurricanes and tropical storms, in the Atlantic Ocean from August to November 2016. The ionospheric disturbances were detected by very low frequency (3-30 kHz) signals from two North American transmitters observed in Algiers (36.75 degrees N, 03.47 degrees E). The results show clear anomalies in the amplitude both at nighttime and at daytime. At nighttime, the anomalies were observed in association with all Large Meteorological Systems even at low stage of storm intensity (tropical depression). The anomalies showed periodicities between 2 and 3 hr with a strong decrease in the signal amplitude. The wave-like features were confirmed by the mother wavelet analysis of the normalized signal amplitude. These signal anomalies may result from traveling ionospheric disturbances generated by tropical storms and hurricanes associated gravity waves.

Plain Language Summary Hurricanes and tropical storms are severe atmospheric weather phenomena that can affect drastically the human life. The effect of this kind of events is not only limited to ground level but also extends through the atmosphere to the high altitudes. One of the most important features of these events, which has an impact on the atmospheric dynamic and possibly climate variability, is the gravity waves (GWs). GWs propagate upward and outward and have been detected up to the top of the ionosphere. This work gives a clear evidence of the GWs effect on the lower region of the ionosphere (50-90 km) and in the middle atmosphere (mesosphere), that have been comparatively less studied. With very low frequency signal analysis we found that the GWs are able to modify the propagation of the radio signals even if the perpendicular distance of the storm center to the signal path is larger than 1,000 km. Additionally, the wavelet analysis of the very low frequency signal amplitude for several days showed a wave-like activity between periods of 2 to 3 hr, which are typical to GWs.