A case study of the mesospheric 6.5‐day wave observed by radar systems

Abstract

In this paper, analysis of wind data detected by six ground‐based radar systems located in equatorial and midlatitude belts shows that a strong mesospheric 6.5‐day wave event occurred during April–May 2003. We compared the global distribution of the observed 6.5‐day wave event with the theoretical wave structure (Rossby normal mode (s, n) = (1, −2)). Additionally, we investigated several important wave characteristics to understand the mesospheric 6.5‐day wave event, i.e., wave period, vertical structure, relationship with background wind, propagating direction, and the zonal wave number. Our results are summarized into three points: (1) the latitudinal structure of the mesospheric 6.5‐day wave during April–May 2003 is basically in agreement with the theoretical Rossby mode (s, n) = (1, −2), although the wave amplitude of zonal wind peaked at the subequatorial latitude of Northern Hemisphere but not at the theoretical place, equatorial region; (2) the main wave periods and the altitude distribution of large amplitude of this wave event varied with latitude; (3) the downward propagating wave phases indicated that this wave event originated in the lower atmosphere and propagated upward to the upper region.

Interhemispheric structure and variability of the 5-day planetary wave from meteor radar wind measurements

“…A wavelet analysis of radar wind measurements at lowto mid-latitudes by Jiang et al (2008) If the 5DW can be amplified by baroclinic instability (Meyer and Forbes, 1997), interannual variability of the 5DW may be associated with interannual variability of the vertical shear because baroclinic instability is associated with a strong vertical shear in the zonal wind. The vertical shear is related to the 11-year solar cycle (Fritz and Angell, 1976) and even has a multi-decadal variability (Aiyyer and Thorncroft, 2011).…”

“…Lima et al (2005) observed the 6.5-day wave using a meteor radar at Cachoeira Paulista (23 • S, 45 • W) and found significant interannual variability in the zonal component, with maximum amplitudes occurring from winter to spring. Jiang et al (2008) employed radar winds at six low-and mid-latitude sites and concluded that enhancement of the 6.5-day wave from April to May is a global-scale phenomenon, maximizing at subequatorial latitudes in the Northern Hemisphere. Furthermore, Kishore et al (2006) employed stratospheric temperature measurements by a Rayleigh lidar at Gadanki (14 • N, 79 • E) and confirmed a stronger 6.5-day wave at lower altitudes than in the MLT.…”

“…These include sea-surface pressure (Madden and Jullian, 1972), temperature (Mechoso and Hartmann, 1982;Prata, 1989;Rogers, 1976), stratospheric height and thickness (Hirota and Hirooka, 1984), geopotential height (Lawrence and Randel, 1996), mesospheric airglow (Sivjee et al, 1994), and winds in the mesosphere and lower-thermosphere (MLT) (Clark et al, 2002;Jiang et al, 2008;Wu et al, 1994). 5DW influences have also been observed in stratospheric ozone (Belova et al, 2008a(Belova et al, , b, 2009Rosenlof and Thomas, 1990), water vapor mixing ratio (Sonnermann et al, 2008), chemical species (Pendlebury et al, 2008), polar mesosphere summer echoes (PMSEs) , mesospheric temperature (von Savigny et al, 2007), noctilucent clouds (NLCs) or polar mesospheric clouds (PMCs) (Merkel et al, 2003(Merkel et al, , 2008Nielsen et al, 2010), and ionospheric parameters (Fraser, 1977;Kokourov et al, 2009;Takahashi et al, 2006).…”

A case study of mesospheric planetary waves observed over a three-radar network using empirical mode decomposition

“…The maximum amplitudes (12-14 m s −1 ) are observed at KOT and PAM radar stations at 94 km of altitude, while moderate amplitudes are observed over the PON radar. Jiang et al (2008) observed that 6.5-day wave amplitudes were strongest between 84 and 98 km, and the maximum amplitude of ∼ 14.5 m s −1 appeared at 92 km in April-May 2004 using the Wuhan meteor radar. Furthermore, they indicated that the 6.5-day waves near the spring equinox were generally stronger than those in other seasons.…”

“…Furthermore, they indicated that the 6.5-day waves near the spring equinox were generally stronger than those in other seasons. A large mesospheric 6.5-day wave was seen during late April and early May 2003 by the SABER instrument aboard the TIMED satellite and the ground-based radar systems (Riggin et al, 2006;Jiang et al, 2008). They mentioned that the 6.5-day wave in the MLT region during April-May 2003 should be regarded as an atmospheric normal mode, which was amplified through sympathetic interaction with the background wind.…”