Because of the importance of gravity waves （GWs） in coupling different atmospheric regions, further studies are necessary to investigate the characteristics of GW propagation in a non-isothermal atmosphere. Using a nonlinear numerical model, we simulate the propagation of small amplitude GWs with various wavelengths in different non-isothermal atmospheres. Our re- sults show that the GW vertical wavelength undergoes sharp changes above the stratopause and mesopause region. Specifically for a GW with an initial vertical wavelength of 5 km, the seasonal background temperature structure difference at 50° latitude can cause the vertical wavelength to vary by -2 krn in the mesosphere and by as large as -4.5 km in the lower thermosphere. In addition, the GW paths exhibit great divergence in the height range of -65-110 kin. Our results also show that the variations of GW path, vertical wavelength and horizontal phase velocity are not synchronized in a non-isothermal atmosphere as in an isothermal atmosphere. Despite the fact that all GWs change their characteristics as they propagate upward in a non-isothermal atmosphere, the variations relative to the initial parameters at a reference height are similar for different initial vertical wavelengths. Our results indicate that the changing characteristics of a gravity wave in a non-isothermal atmosphere need to be considered when investigating the relationship of GWs at two different heights.
Using the method of Thorpe analysis, the TKE （turbulence kinematic energy） dissipation rate （e） and turbulence diffusivity （K） were derived from the RS （radiosounding） measurements in the tropical oceanic upper troposphere. The measurements were performed four times per day during two intense observation periods （May 5-25, and June 5-25） on the Kexue #1 scientific observation ship of SCSMEX （South China Sea Monsoon EXperiment） in 1998. There are three new features obtained from our analysis. First, the responses of e and K to the onset of monsoon are negligible over the ocean at least for the data used here Second, the temporal variations of e and K are in a similar manner and exhibit strong diurnal variations. The diurnal variations achieve their maxima in the morning （08 LT） and early afternoon （14 LT）, and achieve their minima in the evening （20 LT） and early morning hours （02 LT）. The diurnal variations of turbulence parameters （e and K） and their responses to the onset of monsoon are entirely different from those derived over land at similar latitudes. Finally, although the correlations between the variations of e and MCSs （mesoscale convective systems）, which were derived from TRMM （tropical rainfall measuring mis- sion） satellite, are not very well in only few days, the diurnal variations of e averaged over May and June are strongly correlat- ed with the diurnal variations of MCSs with correlation factors of 0.79 and 0.94, respectively. This indicates that the turbulence and its diurnal variations over the tropic oceanic upper stratosphere region are highly related to the MCSs.
A SpectroMeter of Atmospheric RadiaTion （SMART） was developed and installed at the Xinglong station of the National Astronomical Observatories in Hebei province, China, which was supported by the Meridian Project [1]. The experimental tests of spectrometric observation of the hydroxyl emission and rotational temperature in China were conducted for the first time on the night of February 23, 2011 and the night of April 27, 2011, respectively. OH 6-2 band and OH 8-3 band spectra were measured and the rotational temperature was retrieved. Hourly average temperatures （186.82±6.40） K of OH 8-3 band and （178.07±6.73） K of OH 6-2 band were derived from the spectra observed on the night of February 23,2011. Intensities and ro- tational temperature against local time were determined by the spectra measured in the whole night of April 27, 2011. The rotational temperature was consistent with the spatial average temperature of NRLMSISE00 empirical model at height 83-91 km and the average temperature of TIMED/SABER from April to May of seven years at height 83-91 kin, with some discrepancies. The results showed that the new instrument and the retrieval method of the rotational temperature can give reasonable results of the airglow emission of OH and the temperature of mesopause.
