This research studies the medium timescale (6–30 days) ionospheric response over the Wuhan area to solar radiative, recurrent geomagnetic, and lower atmospheric forcing. The ionospheric response is examined by wavelet analysis of the total electron content (TEC) over the Wuhan area from 2001 to 2020. Ionospheric oscillations with periods centering at the harmonic oscillations of the 27-day solar rotation (e.g., 27 days, 13.5 days, 9 days, and 6.75 days) are focused upon. The results show that the quasi-27-day TEC oscillations at the middle latitude have a better overall correlation with solar radiation than recurrent geomagnetic activity, but the correlation between TEC and recurrent geomagnetic activity has a significant increase at the solar minimum stage. As for ionospheric oscillations with periods shorter than 15 days, these oscillations correlate better with recurrent geomagnetic activity. Moreover, a quasi-27-day TEC oscillation event at the middle latitude caused by convective activity from the lower atmosphere was studied. This suggests that lower atmospheric forcing is also an important factor causing ionospheric oscillations. In addition, the ionospheric oscillations over the Wuhan area also show unique regional characteristics, as the regional ionosphere does not respond well to the Kp oscillation with periods shorter than 20 days, particularly, 13.5 days.

We studied the characteristics of quasi-two-day wave (QTDW) using the meridional wind in the mesosphere and lower thermosphere (MLT) obtained from a meteor radar over Kototabang (KB, 0.2S, 100.3E) from 2003 to 2012. Atmospheric oscillations have a crucial impact on atmospheric dynamics, which contributes to more accurate space weather forecasting, thus providing a more secure space environment for human space exploration activities such as remote sensing and satellite navigation. QTDWs are typical atmospheric oscillations in the upper stratosphere, mesosphere and lower thermosphere. The occurrence time, amplitudes, periods and vertical wavelengths of QTDW events are analyzed statistically. Data obtained from the TIMED Doppler Interferometer (TIDI), which can measure wind and temperature and is onboard the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite, are used to analyze the global distribution and spatial structure of QTDWs with different zonal wavenumbers. The characteristics of the QTDWs over KB are compared with the QTDWs at the middle latitudes using the meridional wind data from a meteor radar over Wuhan (114.4E, 30.6N), Beijing (116.5E, 39.9N) and Mohe (121.1E, 50.1N). The amplitudes of the QTDW and spectral analysis are calculated by the least squares fitting method. Our results demonstrate that QTDWs are present almost all year around over KB. The occurrence time, amplitudes, periods and vertical wavelengths of QTDW events with different zonal wavenumbers are determined in this study. We also find that the statistical characteristics of the QTDWs in KB are different from those at middle latitudes. The westward zonal wavenumber −4 (W4) events gradually increase with increasing latitude, whereas westward zonal wavenumbers −1, −2, and −3 (W1, W2 and W3, respectively) events all decrease with increasing latitude.

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Clouds, aerosols and atmospheric molecules are major components of the atmosphere. In the fields of atmospheric physics such as target detection, wireless optical communication and remote sensing, these atmospheric components have a strong attenuation effect on laser transmission. Based on the successive scattering method for solving the radiative transfer equation, the laser transmission model between airborne wireless optical communication terminal and ground-to-air unmanned aerial vehicle (UAV) target in complex atmospheric background is established in this paper. Considering the fact that cirrus cloud, atmospheric molecules and aerosols exist in the real atmospheric background, the variations of direct transmission power, first-order scattering transmission power of 1.55 μm laser emitted by the airborne wireless optical communication terminal with UAV target height are calculated numerically under complex atmospheric background. The effects of the aircraft located at different locations, effective radius of ice crystal particles in cirrus cloud, as well as the horizontal distance between the aircraft and UAV target on received laser transmission power are also analyzed. In the first three examples (i.e., aircraft is above, below, and inside cirrus cloud), laser direct transmission power (LDTP) is much larger than first-order scattering transmission power (FSTP); when the UAV target rises into the cloud, the FSTP is significantly enhanced as a result of the effect of diffraction light. The fourth example is for calculating the variations of LDTP and FSTP with UAV target height for different effective radii of ice crystals. The results show that the LDTP decreases with the increase of effective radius, whereas the FSTP presents an opposite scenario. The fifth example is for calculating the variations of LDTP and FSTP with UAV target height for different horizontal distances. The results show that the LDTP and FSTP decrease with the increase of the horizontal distance, which is obviously realistic. In summary, it is concluded that the laser transmitted power through cirrus clouds is strongly dependent on aircraft position: above, below, or inside cirrus cloud; the horizontal distance between the aircraft and UVA target, and effective radii of ice crystals have great influences on LDTP and FSTP. Compared with the atmosphere above the clouds, the molecules and aerosols below the clouds make the laser power have a strong attenuation. The results given in this paper provide theoretical support for further studying the laser communication experiment in ground-to-air links, UAV formation, command and networking technology in complex atmospheric background.

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