TIMED/SABER Observations Of Quasi-2-day And6.5-day Waves

Planetary waves (PW), with planetary scale, are common atmospheric waves. Their wavenumbers are1-5, and can be observed in various physical quantities. Planetary waves play important roles in thermodynamical and photochemical processes in the atmosphere. Propagating characteristics of planetary waves, as well, are cardinal to energy coupling and transporting in the whole atmosphere. The middle and upper atmosphere is a transition layer of the environment for human survival and the interplanetary space. Thus, researches on the planetary waves in the middle and upper atmosphere are significance in comprehensively understanding of energy exchange processes in solar-terrestrial system.In this paper, global thermodynamical temperatures from2002to2011measured by SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) aboard the TIMED (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics) satellite, global zonal and meridional winds data from2002to2004of the middle and upper atmosphere measured by HRDI (High Resolution Doppler Interferometer) aboard the UARS (Upper Atmosphere Research Satellite) satellite and reanalysis zonal wind data obtained by NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research) are used in order to do research on characteristics of space distributions (along altitude and latitude) and time-variations (day-to-day, seasonal and interannual) of quasi-2-day waves and6.5-day waves. Besides, influences of background wind fields and correlations between interannual variations of atmospheric planetary waves and QBO (quasi biennial oscillation), as well as solar activities, are also discussed. The primary results are summarized as follows:1.2002-2011averaged normalized frequency-wavenumber spectrum of atmospheric planetary waves based on SABER global temperatures are obtained. Spectral results show that, the major wave components of quasi-2-day waves in the Southern and the Northern Hemispheres are (2.13, W3) and (2.04, W4), respectively. While for the6.5-day waves, the main wave components mostly occur in the mid-high latitudes during spring and autumn (Apr.-May or Aug.-Sep.) in both hemispheres.2. During2002to2011, the most remarkable QTDW is (2.13, W3), which happened in the southern summer of2002-2003at32°S from60to90km in altitude. This wave event is analyzed in detail as a case study. The results show that, the largest amplitude of (2.13, W3) is about16.8K, and durations at different altitudes ranges from21to72days. Its downward phase propagation indicates upward propagation of the wave energy and a potential source region below60km. The wave propagated westward and southward in horizontal direction. If horizontal winds are taken into consideration, it shows that background winds play important roles in determining propagating characteristics and wave parameters of planetary waves.3. Basic features of quasi-2day waves from2002to2011are statistically analyzed. It shows that, differences exist between main wave parameters in different hemispheres. Quasi-2day wave activities in the Southern Hemisphere have significantly stronger amplitudes, longer vertical wavelengths and especially stronger dissipations, which haven’t mentioned in the former researches. Furthermore, it is for the first time that we show10-years’interannual variations of quasi-2day waves based on global satellite observations. As a result, quasi-2day waves are seemed to have a quasi-2years’variation period. When QBO (quasi biennial oscillation) in the lower latitude is in its eastward phase, quasi-2day waves demonstrate stronger strengths. It means that, QBO influences on the planetary waves can stretch to higher latitudes. In the year of solar minimum,2009, strengths of QTDWs appear to be anomalous stronger (weaker) in the Northern (Southern) Hemisphere. So, solar activities may have different effects on different hemispheres.4. Basic features of6.5-day wave are extracted using global temperature data measured by SABER. Stronger6.5-day wave activities mainly occur in equinox seasons. We studied latitude-altitude distributions and interannual-latitude variations of (6.5, W1) in spring and autumn, respectively. Latitude-altitude distributions are similar in both seasons. Peaks of the maximum amplitudes usually appear at100-110km in the mid-high latitudes in both hemispheres. On the other hand, interannual-latitude variations of the maximum amplitudes in spring and autumn differ from each other. In spring, interannual variations are similar in both hemispheres. Amplitudes peak in2003-2004, while are relatively weaker in other years. In the Northern Hemisphere, amplitudes are relatively stronger. In autumn, latitudinal distributions are symmetric about the equator. In30°N-50°N, some QBO signal is present. NCEP/NCAR monthly mean zonal winds from2002to2011are used in order to obtain the equatorial QBO. Close relationship is discovered between zonal wind directions of the equatorial QBO and interannual variations of planetary waves in the mid-high latitude.5. Analysis of day-to-day variations of (6.5, W1) amplitudes and phases at40°N in spring and autumn implies that vertical propagations of planetary waves are important to vertical distributions of wave amplitudes. Below100km, amplitude peaks increase with height because of upward propagation of wave energy. Phase profiles indicate that reflection layers or sources for planetary waves may exist above110km. It can lead to downward propagation of wave energy in100-110km and the formation of stationary waves. Vertical structures of (6.5, W1) in spring and autumn are similar. It implies that vertical propagation characteristics in these two seasons are similar as well. Besides, effects of horizontal winds to vertical propagation characteristics of (6.5, W1) are also discussed. Background zonal winds are eastward in52°S-52°N during spring in2003, which is conducive to upward propagation of (6.5, W1). In autumn, background zonal winds are weaker. This may be the reason for larger amplitudes in spring. Background meridional winds have little difference in spring and autumn. As a result, differences of interannual variations of (6.5, W1) amplitudes between spring and autumn may be resulted from differences of background wind field, or from differences of interannual variations of their sources or temperature fields.