Researches On The Dynamics Of The Atmosphere In The Near Space

Near space atmosphere refers to the atmosphere in the altitude range from 20km to 120km,the important part of the earth's middle and upper atmosphere. Many complex couplings related to the Sun-Earth connection under the effects of the solar activity and to the meteorologic variability fill the near space atmosphere, which is highly associated with living environments of human beings, and has significant influences on the spaceflight activities. Therefore, scientists all over the world have paid much attention to the studies of the atmospheric characteristics and their intrinsic mechanisms. Especially in the recent years, the rapid development and application of the near space techniques push the requirements of further explorations and researches of the near space atmosphere. Under this background, some front aspects of atmospheric dynamics in near space are selected for further investigation in this thesis. The works in the thesis are mainly focused on the analysis of the characteristics of the near space atmospheric dynamics and its model studies, which can be summarized as the following seven aspects:(1) Simulations are taken by the NCAR's two dimensional physical model (SOCRATES) to study the climatic characteristics of the atmospheric temperature and wind fields in near space. Those simulation results are compared with the MF radar and the TIMED/SABER observations, which shows consistent features. With the method of combining the observations and the model simulations, the observations of Wuhan and Japanese MF radar and the SOCRATES model are used to analyze the characteristics of the wind fields in the mesosphere and lower thermosphere (MLT). With the results of the simulations, the features of wind seasonal variations at 30oN observed by MF radar are firstly interpreted. Results suggest the importance of the atmospheric gravity waves in determining the MLT wind structures.(2) With the new temperature profiles of COSMIC GPS radio occultation, the potential energies of atmospheric gravity waves are calculated, obtaining the global morphology of stratospheric gravity wave activity. The influences of the origins and the background winds and the modulation of the planetary waves on the gravity wave activity are discussed in details.(3) The temperature measurements from SABER instrument on board of TIMED satellite are used to study the temperature stationary planetary waves (SPWs). Through simulation, the amplitudes of the SPW parameters leaked from the nonmigrating tides due to the non-uniform sampling of the data in the LST domain are first quantitatively calculated. The global temperature SPWs extending from 20-135km by TIMED/SABER are firstly obtained. The SPWs in the upper mesosphere and lower thermosphere (UMLT) are large. These results are significant, especially for the results between 100 and 135km(4) The characteristics of the stratospheric quasi-zero wind layer and its seasonal and geographic variation features over China are obtained by using the ERA-40 reanalyzed wind data. Results show that quasi-zero wind layer generally exists at the height range of 18-25km and some variation of the height of the zero wind line would happen when the time or location change. According to the latitudinal variation of the quasi-zero wind layer, the atmosphere over China could be divided into three parts to discuss its features: low-latitude area (5oN-20oN), transition area (20oN-32.5oN), middle and high-latitude area (32.5oN-55oN).(5) Several methods of deriving horizontal wind fields from satellite temperature data are analyzed and compared in this paper, including the calculation methods of geostrophic wind, gradient wind and balance wind. Taking the temperature data of MLS/UARS in December, 1992 offered by DAAC for example, geostrophic wind, gradient wind and balance wind fields at the altitude range of 20-55km are inferred and compared with ERA-40 reanalyzed wind fields. Results show that, the characteristics of calculated winds are similar with that of the reanalyzed data, indicating that deriving wind fields from the satellite temperature data through theoretical equations is an effective way to supply the gap of lack of wind observations in the 20-60km. Moreover, values and ratios of the terms in balance equations are firstly calculated in this study, and the contribution and relative importance are also analyzed. (6) The observations of COSMIC are used to analyze the variability of the atompshere between 10 and 60km during the sudden stratospheric warming (SSW) in 2007/2008. Results show that the westerly wind is weakened or reversed, and the temperature is cooled during the SSW in the upper stratosphere and lower mesosphere (USLM). Through the wave-mean low interactions, the features are interpreted from the dynamic aspects. Results suggest that the occurrence of the SSW in 2007/2008 may be ralated to the planetary waves, which exceed the critical values, and propagate upward, interact with the mean flow in the upper atostratosphere. Furthermore, through the thermodynamic and continuous equations, the residual circulations are calculated and analyzed, with the results that during SSW, the circulation circles of the residual circulations are reversed.(7) With the 7-year TIMED/SABER observations, a monthly-mean climate model has been developed. The parameters include temperature, pressure, density and horizontal winds. As an example of the application of this model, the atmospheric environments over Beijing, Wuhan, Lasa and Hainan are analyzed. In addition, Artificial neural network (ANN) is used to seek the middle atmosphere modeling with the abundant TIMED/SABER limb observed temperature profiles. A three-layer feed-forward network based on the back-propagation (BP) algorithm has been successfully constructed with the aim of reflecting the monthly mean temperature structure between 20 and 70km in 2007 February. These modeling experiments can provide some reference for future modeling.