Is Mesospheric Quasi Biennial Oscillation Ephemeral?

The time evolution of mesospheric quasi biennial oscillation (MQBO) in the 82–98 km altitude region using long‐term meteor radar observations over low and equatorial latitudes and TIMED Doppler Interferometer (TIDI) observations is discussed for the first time. The wavelet spectra of monthly mean zonal winds over Serpog (6.4°S, 106.7°E; 1993–1998), Koto Tabang (0.2°S, 100.3°E; 2003–2012) and Thumba (8.5°N, 76.9°E; 2006–2015) show the transient nature of the MQBO amplitudes, thus, questioning its perpetuity in the mesosphere‐lower thermosphere (MLT). The time period of the MQBO as well as its amplitude show variability with time. The latitude‐height structures of the MQBO at four time periods (24, 26, 28, and 30 months) are constructed using TIDI measurements, which show diverse latitudinal structure. The significance of the present study lies in bringing out the time evolution of the MQBO and addressing a few outstanding issues on its ephemerality and discrepancies in its amplitudes. Plain Language Summary In the stratosphere and mesosphere of the earth's atmosphere over the equatorial region, there exists a periodic oscillation in the zonal winds with time period varying from 22 to 34 months. This periodic oscillation popularly known as the quasi biennial oscillation (QBO) is well characterized in the stratosphere. However, there have been contrasting observations of the QBO amplitudes and their latitudinal distribution in the mesosphere. Some of the recent studies also questioned about its intermittency as well as its seasonality. In the present study using long‐term observations of zonal winds in the 82–98 km altitude region over the three locations, Serpog (6.4°S, 106.7°E), Koto Tabang (0.2°S, 100.3°E), and Thumba (8.5°N, 76.9°E), the mesospheric QBO is characterized in terms their amplitude and time period. The observed discrepancies in the reported amplitudes and the variability in the time period of the mesospheric QBO are discussed. Using space‐based TIDI observations, the latitudinal distribution of the mesospheric QBO amplitudes at four time periods are also discussed. Key Points The time evolution of the mesospheric quasi biennial oscillation (MQBO) is investigated using long‐term meteor radar observations The results show the intermittent nature of the MQBO Latitudinal distribution of the MQBO in the mesosphere‐lower thermosphere zonal winds is discussed