Long‐Term Study of Quasi‐16‐day Waves Based on ERA5 Reanalysis Data and EOS MLS Observations From 2005 to 2020

Abstract

AbstractThis study uses the latest ERA5 reanalysis data and Earth Observing System microwave limb sounder (MLS) observations to investigate the climatological characteristics of quasi‐16‐day waves (Q16DWs) with different zonal wavenumbers. The fitted temperature amplitudes deduced from ERA5 reanalysis data and from MLS observations are highly consistent with each other, even in fine spatial‐temporal structures. The westward‐propagating wave with wavenumber 1 (W1) and the eastward‐propagating waves with wavenumbers 1 (E1) and 2 (E2) are identified as the most dominant propagating components according to the statistical analyses of their fitted temperature and wind amplitudes. All three waves exhibit significant intra‐annual and interannual variations. Their amplitudes in winter/spring and autumn/summer are strong, moderate, or weak. The W1 wave is more intense in boreal winter than in austral winter, while the E2 wave is the opposite, and the E1 wave is equally strong in boreal and austral winters. Their interannual variabilities measured by the ratios of peak amplitudes in temperature, zonal wind, and meridional wind range from 1.64 to 2.15, indicating significant variability. The presence of intense wave activities is always accompanied by a positive squared refractive index. We suggest that the squared refractive index contributes greatly to the global distribution characteristics of the Q16DWs. The W1 wave in the troposphere is more likely to travel upward and reach the stratosphere and mesosphere, while the intense E1 and E2 waves in the stratosphere and mesosphere may come from the upper atmosphere or be excited in situ.