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OBSERVATIONS OF THE QUASI 2-DAY WAVES IN THE MESOPAUSEOVER WUHAN, CHINAJ. Xiong ∗ , W. Wei, B. Ning and L. Liu(Wuhan Institute of Physics and Mathematics, The Chinese Academy of Sciences, Wuhan, China)1. IntroductionNumerous studies of the mesospheric quasi 2-day wave have been conducted in the lasttwo decades. Most measurements by radars suggest the quasi 2-day wave is predominantly asummertime phenomenon (e.g., Thayaparan et al., 1997; Namboothiri et al., 2002). Manyobservations by satellite showed strong occurrence of the quasi 2-day waves (Wu et al.,1993). Those preponderance of observational evidence of a recurrent quasi 2-day oscillationin the middle atmosphere led Salby (1981) to suggest that the disturbance was amanifestation of the third Rossby-gravity normal mode of a windless, isothermal atmosphere.However, Meek et al. (1996) examined the Northern Hemisphere zonal wave number andconcluded that the wave number of that event may sometimes be 4. Plumb (1983) proposedthat 2-day wave observed in summer may be the results of baroclinic instability near thesummer stratospheric wind jet. Although the two theories were supported by observations,there is not consistent explanation for the quasi 2-day wave in the mesosphere and lowerthermosphere. Since the quasi 2-day wave is important to the global dynamics of theatmosphere, further observations and theoretical study are needed.We will report the vertical and temporal structure of quasi 2-day wave observed atWuhan (30.6 o N, 114.5 o N) by a newly established meter radar.2. DataThe Wuhan meteor radar is an all-sky interferometric broadband radar system which hasalmost identical characteristics to the Buckland Park meteor radar in Australia and theSKiYMET radar in Canada (Hocking et al., 2001). The parameters used for routineobservations are shown in Table 1.Table 1 Wuhan Meteor Radar SpecificationsParameterValuePeak power7.5kWFrequency38.5MHzPRF500Hz (Feb. 2002 to Sep. 2002 )1980Hz (From Oct. 2002)Range sampling resolution 2kmThe data from Feb 2002 to Oct 2003 have been used in the present study. The zonal andmeridional winds for every 2h and 2km step are obtained from the measured radial windvelocity. Generally, we chose a time window of 8-day length for deriving quasi 2-day waveparameters, using the harmonic analysis and Lomb-Scargle periodogram methods.160∗ Corresponding author. E-mail address: xjg@wipm.ac.cnThis work is supported by the National Natural Science Foundation of China (No.40174048 and 40134020).