“…In order to investigate the global structure of the W3 and W4 components, we extract the amplitudes of the W3 and W4 modes in the zonal and meridional winds and temperature from the reanalysis data by using a two‐dimensional least squares fit. Considering that the W2 component arises frequently in the MLT (Fritts et al.,
2019), the W2 mode is also fitted together. The fitting expression is written as
where the subscript
= 1, 2 and 3 denotes the W2, W3, and W4 modes;
is the longitude in units of radian;
is the time;
represents the fitted quantity, that is, the zonal wind, meridional wind and temperature, respectively;
denotes the mean value of the fitted quantity;
and
are the amplitudes and initial phase, respectively;
= 46 hr is the period of the QTDW; and
= −2, −3 and −4 denote the zonal wavenumber of the W2, W3, and W4, respectively.…”