海南地区中高层大气重力波活动的激光雷达研究

In the early of 2010, Hainan lidar station was built by National Space Science Center in co-operation with Hainan Normal University. As one important part of Meridian Project, it is designed to observe the density and temperature variations of middle and upper atmosphere over Hainan Island. Based on these constantly observations from this station, the lidar study of atmospheric gravity wave (AGW) activities in middle and upper atmosphere over Hainan Island is proposed by us..In this proposal,the atmospheric density fluctuations caused by AGWs will be obtained by analyzing the observation data. Parameter values of each AGW, including wavelength, period, wave phase speed, wave amplitude and growth factor, will be procisely extracted. Seasonal variation characteristics of AGWs over Hainan Island will be analyzed according to the seasonal distributions of those parameter values. The relationships between parameters will be discussed in terms of diffusive filtering theory (DFT). Furthermore, the nightly and seasonal variations of AGW activity will be analyzed, and the temporal correspondence with the seasonal variations of temperature and background winds in troposphere and stratosphere be investigated. Since Hainan Island is close to equator and its climate is mainly dominated by oceanographer,correlations of AGW activities with convections above sea, meridional advections of summer hemisphere westward winds and typhoons will be focused. Characteristics of AGW sources will be investigated in detail. The formation mechanisms of distinct regional characteristics of AGW activities will be explained from two aspects,one is how the source intensity and frquency is determined by the seasonal variation of temperature in troposphere, the other is how the upward wave propagation is influenced by the background mean flow.We believe that the main contributors to AGW activity are from sources in troposphere and stratosphere below 20 km, and the seasonal variation of this activities may be principally ascribed to the seasonal change of temperature and background winds. Frequency and intensity of AGW sources are dependent on the incidence and strength of convection, which are related to the seasonally changed temperature in troposphere. Effects of background wind (including typhoons), especially those of dissipation and filtering, are important to the upward propagations of the generated AGWs..In the cooperation frame of Meridian Project, we will compare our observation results with those obtained at Beijing lidar station, Wuhan lidar stations and Hefei lidar station. Latitude-dependent AGW activities in different seasons in middle and upper atmosphere above China will be investigated.It will be meaningful to the comprehensive understanding of regional characteristics and formation mechanisms of AGW actitities above our country.

本项目基于海南师范大学与中国科学院空间中心联合共建的海南激光雷达观测站，实现对海南地区中高层大气重力波的夜间连续观测。拟通过数据反演得到中高层重力波的大气密度扰动廓线，提取重力波的波长、周期、波速、振幅和增长因子等参数值。分析重力波参数分布特点以及参数间的关系，得到大气重力波活动的夜间和季节变化特征。分析海洋对流、赤道潜流、天气突发事件（台风等）与大气重力波活动的相关性，探讨该近海低纬度地区重力波的波源特性。分析大气重力波活动的季节性变化与对流层的温度和风场的季节变化关系，研究该地区背景风场对重力波传播的影响。同时从波源特性和背景大气影响的角度给重力波活动的区域特殊性作出相应的解释。对照北京（中纬度）、武汉和合肥（中低纬度）地区重力波活动的观测研究结果，全面分析我国高、中、低纬度上空重力波活动的季节性变化特征，得到重力波活动的纬度相关性，全面理解我国上空重力波活动的区域特殊性及其形成原因。

基于国家重大科学基础建设“子午工程”项目的激光雷达链对海南、合肥和北京大气活动长期监测，本项目[No. 41264006]完成了我国低纬度-中纬度-中高纬度中高层大气活动特征的研究工作，内容如下：.①完成了激光雷达对海南上空中高层大气活动长期监测.自2010年起，海南激光雷达正常运行了6年，积累了大量的中高层大气活动和环境变化的科学监测数据，公布于http://www.meridianproject.ac.cn，服务于国际空间天气和环境变化监测的需要。.②完成了激光雷达信号的有效校正工作。通过模拟实验，完成了雷达信号中的信号感应噪声、光电倍增管的非线性效应以及光子堆栈效应等带来的误差分析和矫正工作，使得激光雷达的密度、温度测量结果与SABER-TIMED卫星的实时观测数据以及NASA的标准大气模型数据结果有很好的一致性。.③完成海南、武汉、合肥和北京上空钠层日变化和季节变化的研究工作。发现钠层变化具有明显的纬度相关性，钠层日变化主要受周期性潮汐波活动和钠层光化学反应影响；钠层季节变化则与钠层温度相关的化学反应的季节变化直接相关。.④完成了海南、合肥和北京上空中层顶重力波活动的监测与研究工作。发现北京和合肥上空重力波活动与青藏高原上的地形和强对流产生的重力波季节变化直接相关，季节性变化的背景风场对重力波活动的季节性变化也产生了明显影响。海南岛上空重力波的波源也主要来自青藏高原，同时南海的强对流和赤道潜流产生的重力波也直接影响激光雷达的观测结果。.⑤完成了海南和北京上空中高层大气密度和温度的激光雷达探测以及钠层突发、钠层密度翻转等大气现象的研究工作。.本项目完成的研究工作，有效地拓宽了人们对中高层大气活动、能量和动量、以及物质交换的动力学过程的认知。有助于人们从气象学和大气动力学角度理解地球大气的变化机制，进而掌握空间天气的变化规律；对当前“数字化地球”、“全球气候参数化”模型的建立，具有实际指导作用。更为重要的是，海南岛中高层大气活动的监测研究，填补了世界上低纬度濒海地区大气活动研究的部分空白。