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.
In this paper, globally-averaged, thermospheric total mass density, derived from the orbits of -5000 objects at 250, 400, and 550 km that were tracked from 1967 to 2006, has been used to quantitatively study the annual asymmetry of thermospheric mass density and its mechanism（s）. The results show that thermospheric mass density had a significant annual asymmetry, which changed from year to year. The annual asymmetry at the three altitudes varied synchronously and its absolute value increased with altitudes. The results suggest that there is an annual asymmetry in solar EUV radiation that is caused by the difference in the Sun-Earth distance between the two solstices and the random variation of solar activity within a year. This change in radiation results in an annual change in the thermospheric temperature and thus the scale height of the neutral gas, and is the main cause of the annual asymmetry of thermospheric mass density. The annual asymmetry of mass density increases with altitude because of the accumulating effect of the changes in neutral temperature and scale height in the vertical direction.
MA RuiPingXU JiYaoWANG WenBinCHEN GuangMingYUAN WeiLEI JiuHouAlan G BURNSJIANG GuoYing
