北京地区大气温度及重力波活动的季节变化

利用瑞利激光雷达观测数据，分析了北京地区35~70km高度范围内大气温度和重力波活动的季节变化.发现北京地区30~70km高度范围内的大气温度有明显的年周期变化:平流层顶最高温度出现在6，7月份，大约为270K；中间层70km高度最低温度也出现在6，7月份，大约为200K.以2014年10月14日晚数据为例，分析重力波势能密度，发现50km以下重力波势能存在耗散，而在50km以上重力波近乎无耗散地向上传播.通过对比35~50km高度范围内的平均势能密度，对北京地区重力波活动强弱的季节变化进行了研究.研究结果表明，北京上空重力波活动强度具有明显的年周期变化，冬季平均势能密度为18J·kg-1，夏季为8J·kg-1，且冬季重力波活动强度约为夏季的两倍.此外，还分析了春夏秋冬四个季节重力波势能密度随高度的变化.结果表明，不同季节和不同高度的重力波势能密度不同. 

Seasonal Variation of Atmospheric Temperature and Gravity Wave Activity over Beijing Area

By using Rayleigh lidar data, the seasonal variations of atmospheric temperature and gravity wave activity at 30~70km height over Beijing area are analyzed. Results show that the atmospheric temperature has an obvious annual cycle variation. The highest temperature in the stratopause appears in June or July, which is about 270K. The lowest temperature at 70km height of the middle layer also occurs in June or July, which is about 200K. Taking the data of 14 October 2014 as an example to analyze the potential energy density of gravity wave, we find that dissipation exists in the potential energy of gravity waves under 50km height, while gravity waves propagate up with no dissipation over 50km height. Using the average potential energy density at 35~50km height, the seasonal variation of the gravity waves activities intensity is analyzed. The gravity waves activities have an obvious annual cycle. The average potential energy density is 18J·kg-1 and 8J·kg-1 in winter and summer respectively. The gravity waves activities intensity in winter are about two times of that in summer. In addition, the variation of gravity waves potential energy density with height in spring, summer, autumn and winter are analyzed. The analysis shows that the potential energy density of gravity waves is changing with different seasons and heights.