突发钠层的地区特性及其机理的研究

The upper mesosphere and lower thermosphere(MLT) is the connection of the lower atmosphere and the upper atmosphere.It is so important to consider the Kinetic Processes of the MLT when we refer to the running modle of the whole atmosphere, the globle climate change and the lower atmospheric response to the solar activities.The meteor injections consist of a metal layer full of sodium, iron and calcium atoms and their ions located on the MLT region of 80km to 110km.The feasibility to probe the density of metal atoms for their fluourescence resonance effects by groundbased lidars once make up for the blank in the MLT detect as its height is too high for foundation means and too low for the space based devices. The Sporadic Sodium Layer (SSL or Nas) is a hot topic among all the phenomena on the metal layer for its conspicuous features such as the sharp increase of sodium atoms within a moment and its complicated processing mechanism which is still unclear although studied for over 30 years and many possible mechanisms proposed. The SSLs, not only cause a large quantity of sodium atoms, but also have a relationship with the ionospheric Sporadic E Layers (Es),the wind shear caused by gravity waves and tides, and the temperature variations of the mesopause. In this project, we design to select the Nas events from lidar observations by the four sites ( Hainan, Wuhan, Hefei and Bejing) of the Meridional Project, count the frequences for each site to obtain the regional characters of the SSLs. And then,we will check the ionosphere situations from the Digital Height Gauges of Hainan, Wuhan and Beijing to acquire a statistical correlation between the sporadic sodium layers and sporadic E layers. On this base, we can choose some typical SSLs events to discuss individually. The ionosphere Height Gauges make it available to know whether an SSL event is accompanied by an Es or not. For Hefei site, there is a newly operated wind and temperature lidar which can make a simultaneous observation with the current sodium lidar so that the influences on the sodium density caused by the wind shear and temperature variations will be seen clearly. After that, it is possible to do deep research into the whole forming processes of the sporadic sodium layers as we have a large quantity of data accumulation for the sodium density, ionospheric disturb and wind shear.

中高层大气是衔接低层大气与高层大气的枢纽，也是日地之间能量传递的桥梁。研究中高层大气动力学过程对于了解整个大气层的运行模式、全球气候变化以及低层大气对于太阳活动的响应有着不可忽视的作用。在中高层大气各种自然现象中，突发钠层由于其显著的特征和极其复杂的发生机制，至今仍是国际上的研究重点和热点。突发钠层发生时钠原子密度剧烈增加的现象，被认为与电离层突发E层、风场剪切以及温度变化等过程密切相关。本项目拟根据子午工程同一子午线上四个不同台站（海南、武汉、合肥以及北京）的激光雷达数据，统计各地突发钠层事件并得出其区域性特征，并与海南、武汉和北京的电离层数字测高仪数据进行比较，统计不同地区突发E层的平均强度，分析突发钠层与突发E层的统计学相关性。在此基础上，再选取其中的典型突发个例，与电离层和风场的同步观测资料进行综合研究，重现由于突发E层形成的高浓度电子和大气风场剪切作用造成钠原子密度陡增的全过程。

中高层大气是衔接低层大气与高层大气的枢纽，也是日地之间能量传递的桥梁。研究中高层大气动力学过程对于了解整个大气层的运行模式、全球气候变化以及低层大气对于太阳活动的响应有着不可忽视的作用。利用北京、合肥、武汉以及海口等4个激光雷达站点观测数据. 我们统计研究了突发钠层(SSLs)和热层增强钠层(TeSLs)的特征。突发钠层发生频率较高， 而热层增强钠层发生较少，可能跟突发E层（Es）关联较大。在突发E层期间（foEs>4 MHz），4个站点观测到的突发钠层和热层增强钠层呈现出明显地增强。另外，我们提出了亚热带地区的突发钠层的机制——四步冰尘埃颗粒钠储库机制。这个模型与许多观测吻合的很好。进一步地，我们研究了不同纬度及其不同高度上的突发钠的特征和可能的机制。不同纬度，不同季节，突发钠层发生的高度也有所不同。冬天突发层很少出现在96km以上，但是在夏天，却很常见。这可能与不同的突发钠层形成机制有关。在亚热带地区的合肥和武汉，突发钠层与高的背景大气温度有很大的关联性，但与突发E层关系相对较弱。在低纬度的海口，发生在96km以下和以上的突发钠层分别与高的背景大气温度和突发E层有较强关系。在中纬度地区的北京，突发钠层发生较低，同样与背景大气温度和突发E层相关。这地区的突发E层经常会形成双钠层结构。

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