Resolving daily wave 4 nonmigrating tidal winds at equatorial and midlatitudes with WINDII: DE3 and SE2

Abstract

The Wind Imaging Interferometer observed nonmigrating tidal winds from 90 to 260 km during daytime and at 99 and 250 km during the night and found that the amplitudes and phases of the daytime and nighttime extracted wave 4 for a given day were different, indicating the presence of more than one component. The objective of this study is to resolve those components. Local time versus longitude propagation plots over individual seasons revealed the diurnal eastward propagating wave number 3 (DE3), the semidiurnal eastward propagating wave number 2 (SE2) and the stationary planetary wave number 4 (SPW4). Using a fitting procedure for individual days it was then found possible to determine the amplitudes and phases of DE3 and SE2 and the amplitude of SPW4 for each day, using a constant phase for the SPW4 obtained from the propagation plot. These DE3 and SE2 values were compared with data‐constrained model results yielding good agreement at 99 km but with mixed agreement at 250 km. Time series analysis of 164 days duration showed considerable variability in the amplitudes of the zonal wind for DE3 with the SPW4 tending to follow; DE3 power spectral peaks occurred near 12, 16, and 32 days. The SE2 showed less variability, also displaying spectral peaks but shifted from the DE3 peaks. Monthly averages of the DE3 and SE2 show that the DE3 is predominant at the equatorial mesosphere/lower thermosphere region. On the other hand, the SE2 is uniformly present at lower and midlatitudes and all altitudes.

WINDII airglow observations of wave superposition and the possible association with historical “bright nights”

“…Cho and Shepherd [2015] showed that the WINDII longitudinal variations of winds could be fitted with zonal wave numbers 1-4. Cho and Shepherd [2015] showed that the WINDII longitudinal variations of winds could be fitted with zonal wave numbers 1-4.…”

WINDII observations of thermospheric O(1D) nightglow emission rates, temperature, and wind: 1. The northern hemisphere midnight temperature maximum and the wave 4

“…WINDII provided highly accurate measurements of volume emission rates (VERs) with standard deviation estimates for the airglow VER of 1 photon cm À3 s À1 at night and 6 photons cm À3 s À1 during the day, while for the neutral wind and Doppler temperatures these are 4 m s À1 and 11 K at night and 7 m s À1 and 20 K during the day, respectively [Shepherd et al, 1993;Gault et al, 1996]. Examples of wind profiles and their errors have been presented by Cho and Shepherd [2015], who showed that the standard deviation of the O( 1 D) zonal wind varies with height with a peak of~18 m s À1 at 230 km and 7 m s À1 at 270 km, consistent with the calculated standard deviation; an example of this was given in their Figure 1d. [Walsh, 1950;Environmental Protection Agency, 1998.…”

“…Various studies [ Bruinsma and Forbes , ; England et al ., ; Oberheide et al ., ; Cho and Shepherd , ] demonstrated the importance of the eastward propagating semidiurnal tide with zonal wave number 2 (SE2) for the generation of the wave 4 signatures observed in the upper atmosphere. Miyoshi et al .…”

“…Various studies [Bruinsma and Forbes, 2010;England et al, 2010;Oberheide et al, 2011;Cho and Shepherd, 2015] demonstrated the importance of the eastward propagating semidiurnal tide with zonal wave number 2 (SE2) for the generation of the wave 4 signatures observed in the upper atmosphere. Miyoshi et al [2012] examined the vertical structure of the SE2 and DE3 in neutral density and their influence on the wave 4 structure at various altitudes in the thermosphere employing the Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy model and found that while the DE3 amplitude has a peak at the equator and the phase distribution is symmetric around the equator, the neutral density SE2 amplitude maximizes at middle latitudes, with latitude phase structure indicating the dominance of the asymmetric mode of the SE2 in the thermosphere.…”

MIPAS observations of longitudinal oscillations in the mesosphere and the lower thermosphere: climatology of odd-parity daily frequency modes

“…The analyses are based on observations of wind fields (see, e.g., Oberheide and Forbes, 2008a;Talaat and Lieberman, 2010;Lieberman et al, 2013;Cho and Shepherd, 2015) or atmospheric species emission rates or abundances (see, e.g., Oberheide and Forbes, 2008b;Oberheide et al, 2013;Nee, 2014) or the ionized atmosphere (see, e.g., England et al, 2006;Chu et al, 2009;Mukhtarov and Pancheva, 2011). Few global observations of the neutral atmosphere are available in the 100-150 km altitude range.…”