Abstract
AbstractClimatology of lunar semidiurnal (LSD) oscillations is constructed using a decade of meteor radar observations over low and equatorial latitudes, and their response to sudden stratospheric warming (SSW) events is discussed. Meteor radar‐measured hourly zonal and meridional winds in the 80–100 km region over Thumba (8.5°N, 76.9°E) and Kototabang (0.2°S, 100.3°E) have been used to extract the LSD amplitudes during the years 2006–2015 and 2002–2012, respectively. The similarities/discrepancies in the climatology of LSD over low and equatorial latitudes as compared to Vial and Forbes lunar tidal model outputs are discussed. The present results obtained using four individual cases over Thumba and Kototabang indicate that the amplitudes of LSD show pronounced enhancement during polar vortex weakening (PVW) events rather than the conventional SSW events. Case studies presented in this study are characterized by simultaneous occurrence of enhanced LSD amplitudes and reduced solar semidiurnal (SSD) amplitudes, together with the presence of a quasi 16 day (Q16D) wave. Thus, present results corroborate the existence of nonlinear interaction between the Q16D wave and the SSD in the equatorial latitude and low‐latitude mesosphere lower thermosphere (MLT) region during PVW/SSW events and their potential contamination to LSD amplitudes. Further, using ground‐based magnetometer measurements from the dip equatorial site Tirunelveli (8.7°N, 77°E, 0.23° dip angle), LSD amplitudes in EEJ intensities are also estimated. An excellent association is found between the temporal evolution of LSD amplitudes in zonal winds at MLT region and in the intensity of EEJ, providing a paradigmatic example of MLT‐ionosphere coupling.
Published Version
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