By using a two-dimensional, full-implicit-continuous-Eulerian (FICE) scheme, we simulated the nonlinear propagation and evolution of gravity wave paekels in a compressible, nonisothermal and dissipative atmosphere. The numerical results show that when an upgoing gravity wave packet is generated in the lower mesosphere, it can propagate along gs ray path until it reaches lower thermosphere. However, upon reaching the lower thennosphere, the wave packet and associated energy propagate ahnost horizontally, which departs obviously from the prediction of linear gravity wave theory under WKB approximation in the nondissipative case. Further discussion indicates that the influences of nonlinearity and background temperature are not strong enough to restrict completely the upward energy propagation of the wave packet and that the influence of constant molecular viscosity on the characteristics (energy propagation path and wave parameters) of gravity waves is insignificant. It is the vertical inhomogeneity of molecular viscosity that causes the restriction of upward energy propagation of the gravity wave packet Moreover, througheut propagation, the donlgrant vertical wavelength of the wave packet decreases with time, as it is affected by the joint actions of nonlinearity, background temperature, and dissipation. These results indicate that the molecular viscosity, especially the vertical inhomogeneity of molecular viscosity, plays an important talc in the nonlinear propagation of gravity wave packets.

Here is die first report on the observation of meteor ablation trails with tidar in China. Four long-lived Na ablation trails were el)served during the 18/19 Nov, 2001 Leonid meteor shower with a sodium resunance lidar over Wuhan. The Mean altitude of the 4 trails is 97.95kin. coaststeal with Leonid high entry velocity (-72kn/s). The peak deusit) averages about 3380

By using a full-implicit-continuous-Eulerian (FICE) scheme and taking a set of basic atmospheric motion equations in spherical coordinates as governing equations, z fully nonlinear numerical model for the dynamics of the middle and upper atmosphere is established to numerically study the nonlinear global propagations and amplitude growths of large-scale gravity wave packets. The simulation results show that the newly established model can successfully exhibit the essential characteristics of the global propagations of gravity waves: wave energies propagate upward along the ray paths derived from the hnear gravity wave theory, and wave disturbance amplitudes increase with the increasing heights. During the upward propagation of gravity wave packets, there occurs evident enhancement of background wind along the propagation direction. Moreover, our simulation demonstrates that Earth rotation has little influences on the wave energy propagations and amplitude growths. However, the primary nonlinear curvature terms (uvr tan0 and -u2r tan0) play an important role in the growths of gravity wave amplitudes, which causes a evident latitudinal dependence of wave amplitude growth. In the Northern Hemisphere, with the same spatial scales and initial zonal dislurbance amplitudes, the waves propagating in lower-latitude regions have larger disturbance amplitudes.

Winds and waves measured by the Medium Frequency Radars (MFR) at Saskatoon (52N, 107W), Robsart (49N, lg9W), and Sylvan Lake (52N, 114w), and the Fabry-Perot Interferometer (FPI) at Saskatoon are compared. Particular care has been taken to exclude FPI airglow (558 nm, green line) contamination by aurora or scatter from clouds; radar data were setected from high slgnal-to-noise conditions. Comparisons between the MFR/FPI in seasonal wind climatologies (at a radar height of 98km) and wind speed ratios and direction-difference histograms for the Saskatoon systems show excellent agreement. Zonal and meridional wind comparisons (scatter plots) also show no significant differences in mean winds between the FPI and MFR. Differences between instantaneous measurements, as seen on 91 individual days, are categorized into four types of events, depending upon FPI/MFR similarities and differences and the dominance of the solar tide A gravity wave model is then used to demonstrate the effects of waves, with scales from hundreds to several thousand of kilometers, upon such optical and radar systems, each of which has a different inherent spatial averaging. The model is largely successful in explaining the differences between the instantaneous MFR and FPI measurements. The relevance of such comparisons to satellite/ground-based collaborations is briefly discussed.

Based on lidar measurements beteen March and September 2001, the charccteristics of sporadic Na layers (Na, layers) over wuhan (30.5