Analysis Of The Middle Atmosphere And Lower Thermosphere About The Background And Waves During The Sudden Stratospheric Warming Event

Complex chemical reactions, rich dynamical process and many interesting physical phenomena exist in the middle and upper atmosphere(MU) at the range of 10-100 km from the ground. Researches and explorations about the middle and upper atmospheric characteristics, changing process and the internal mechanism will contribute to understand some scientific problems, such as global atmospheric change, coupling between different atmospheric levels and the relationship of solar-earth. The chemistry, thermodynamics and kinetics in the MU are very complicated and the the observational data is not enough. So the characteristics of the MU and its changes are still not comprehensive at some degree, and there are many issues that require discussion by now. Among them, the stratospheric sudden warming(SSW) which occurs in the winter polar stratosphere is atmospheric obvious, abrupt and irregular phenomenon. When the SSW happens, the polar stratospheric temperature experiences a sharp rise within a short time as well as the circulation structure transforms. The SSW affects the global atmosphere and ionosphere, influences troposphere weather system, impacts the distribution of stratospheric trace gases, contributes to ionosphere anomaly absorption. In addition, the SSW, which has a close relationship with mesosphere cooling and lower thermosphere warming, also plays an important role in the atmospheric coupling process.In this thesis, our research uses wind field data detected by five low-middle latitudinal meteor radars which are located in a chain near 120°E of the northern hemisphere, the ERA-interim reanalysis data of the European Centre for Medium-Range Weather Forecasts(ECMWF) and the atmospheric temperature field data of SABER/TIMED. We analyzed the MU of the northern hemisphere during the winter of 2013/2014 in order to observe the atmospheric coupling situation and waves during the SSW event. The main results are as follows:1. There are horizontal and vertical atmosphere coupling during the SSW event, the specific performance in atmospheric temperature field are as follows. When the SSW occurs, the polar stratosphere temperature increases anomaly while the mesosphere experiences the anomaly cooling, as well as the thermospheric temperature rises. Along the meridional direction, the low latitude stratosphere becomes abnormally cool, at the same time the temperature of the MLT region anomaly increases. Besides, the global scale view of the SABER temperature field shows double-humped structure near the mesospause(~90km) during the SSW in the meridional direction. That is the well-known mesospheric cooling over the northern hemispheric high latitudes turns to warming over the mid-latitudes then reverts to cooling near the equatorial regions. Furthermore, the trend continue into the southern hemisphere of which the warming occurs again at the mid-latitudes.2. The wind field of two low-latitude stations is basically consistent with the HWM07 model. The daily mean zonal and meridional wind will be reversed at Fuke and Qujing stations when the SSW event happens. The eastward wind in the lower MLT region(below 88km)is reversed to weatward, the trend of which is contrary with the upper MLT. The wind field of the upper MLT has exist several transient reversals before the occurrence of the SSW, the inversion will extended downward until the eastward wind of the lower MLT turns into weatward completely.3. The enhanced quasi 16-day PWs can be found at the MLT region during the January SSW and the enhancement of quasi 16-day waves prior to the warming. The quasi 16-day PWs had mostly the strongest amplitude when the polar temperature reach its peak. The quasi 16-day PWs found at the low and middle latitude MLT region are similar with the normal mode(1,-4) at some degree, but there are some deviation on the wave intensity distribution. The amplitude peak of detected waves show at lower latitude than the classical theory, which demonstrates the quasi 16-day PWs are also modulated by the complex change of background atmosphere. In the horizontal direction, the phase of waves detected by the meteor radar lag with the latitude increasing. In the vertical direction, there is a upward propagation trend of waves from the stratosphere. The change of planetary waves in the MLT region atmosphere and the occurrence of the SSW exist overlapping, which indicate there may be some relationship between the dynamic processes of the MLT region and the stratosphere.4. The band pass filter of the stratospheric temperature shows that quasi 16-day PWs propagated period lower latitude to the pole, meanwhile the zero-wind line moved from low latitude to high latitude, indicating a dynamical connection between the 16-day PWs and SSW.