Researches On The Variations Of Atmospheric Winds In Near Space At Mid-latitude

The near space atmosphere between 20 and 100 km is focused on, including stratosphere, mesosphere and lower thermosphere, which is an important part of the earth atmosphere. Many complex phenomenons exist in this region, which are effected by solar activities and meteorological variability. The atmospheric winds play important roles in the transport of energy and momentum, which can influence the dynamics and circulations in near space. There are variations with multiple spatial and temporal scales in mid-latitude, which is unique from the other latitudes. So, the observations and analysis of winds contribute to learn the characteristics of near space over mid-latitude and study the coupling of global atmosphere.The work in this thesis can be summarized as the following aspects:(1) The climatic features of zonal mean zonal wind and meridional wind are simulated by WACCM. The simulations are compared with the MERRA data and URAP data. The results show that WACCM can reproduce atmospheric wind structures similar to observation, especially in northern hemisphere. So, WACCM model can be used to study the winds in near space over mid-latitude.(2) The features of the mesospheric and lower thermospheric mean winds within 80-100 km altitude regions are investigated by wind data from the observation of China Langfang(39.4°N,116.7°E) meteor radar. The results show that the mean zonal winds and mean meridional winds both have obviously seasonal variations. During the winter, eastward winds prevail in the MLT ranges, which is strong in mesosphere and decrease versus increasing altitude. In the summer, westward winds dominate in mesosphere, and decrease along with increasing altitude, then turn to the strong eastward in lower thermosphere. The wind evolution in the spring and autumn are the transition characters between the summer and winter. The mean meridional winds are southward in summer and northward with sometimes reversal in winter, in general. The above main seasonal variations of mean winds are captured largely by the simulation of WACCM model, which is similar to the HWM93 model.(3) The seasonal variations of tides of the mesospheric and lower thermospheric(MLT) winds within 80-100 km altitude regions are studied by using wind data from the observation of Langfang(39.4°N,116.7°E) meteor radar(MR). The results show that both diurnal and semidiurnal tide dominates the zonal and meridional wind, having obviously seasonal variations. A semiannual variation is found in diurnal tide below 88 km with maxima in February-March / October and minima at summer and winter, whereas the diurnal tide above 88 km has annual variation with amplitude peaking in February at 92 km, with the zonal and meridional component is 42 m/s and 38 m/s. The phase of diurnal tide in autumn and winter leads that in spring and summer. The semidiurnal tide has semiannual variation that strong in May and September and weak at summer and winter. The phase of semidiurnal tide in spring and summer leads that in autumn and winter. WACCM can reproduce the seasonal variation of tides, but underestimate the amplitudes. Moreover, the comparison between the tides over Langfang with other stations at about 40°N latitude indicts the tides variation depending on longitude.(4) Based on the data at ~40°N at different longitudes during different Stratospheric Sudden Warming(SSW) events, the responses of zonal winds in the stratospherie,mesosphere and lower thermosphere to SSWs are studied in this paper. The variations of zonal wind over Langfang, China(39.4°N, 116.7°E) by MF radar and the Modern Era Retrospective-analysis for Research and Applications(MERRA) wind data during 2010 and 2013 SSW and over Fort Collins, USA(41°N, 105°W) by lidar and MERRA wind data during 2009 SSW are compared. Results show that the zonal wind at ~40°N indeed respond to the SSWs while different specifics are found in different SSW events or at different locations. The zonal wind has significant anomalies during the SSWs. Over Langfang, before the onset of 2010 and 2013 SSW, the zonal wind reverses from eastward to westward below about 60-70 km and accelerates above this region, while westward wind prevails from 30 km to 100 km after the onset of 2010 SSW, and westward wind prevails in 30-60 km and 85-100 km and eastward wind prevails in 60-85 km after the onset of 2013 SSW. Over Fort Collins during 2009 SSW, eastward wind reverses to westward in 20-30 km before the onset while westward wind prevails in 20-30 km and 60-97 km and eastward wind prevails in 30-60 km and in 97-100 km after the onset. Moreover, simulations by the specified dynamics version of the Whole Atmosphere Community Climate Model(SD-WACCM) are taken to explain different responding specifics of zonal wind to SSW events. It is found that the modulation of planetary wave(PW) plays the main role. Different phases of PWs would lead to the different zonal wind along with longitudes and the different amplitudes and phases in different SSW events can lead to the different zonal wind responses.(5) The variability of the atmosphere between 20 and 100 km over middle latitude is diagnosed by the simulation of 2012/2013 SSW by SD-WACCM. The results show that: during the SSW, the activities of planetary waves(PW1, PW2) enlarge and play a major role; the eastward propagating gravity waves transform to the MLT and force the wind to eastward; the residual circulation change obviously, which effect the zonal wind and temperature.