北纬30°中层顶区域钠与铁原子层的结构和年际变化

基于武汉大学Na和Fe激光雷达在2004年1月至2011年12月期间的观测数据，得到武汉上空中层顶区域Na和Fe原子层的平均特性、夜间变化和季节变化特征.Na层平均质心高度为91.36km，平均RMS（均方根）宽度为4.64km.Fe层平均质心高度为88.99km，平均RMS宽度为4.57km.在充分考虑金属层夜间变化和季节变化对数据样本影响的基础上，获取了Na层和Fe层结构在此期间的年际变化特征.对Na层和Fe层质心高度及RMS宽度的年际变化进行线性拟合，发现Na层和Fe层在此期间均相对稳定，Na层质心高度在近8年间仅有约58m的下降，变化率为-7.91m·a-1，Na层RMS宽度减小约151m，变化率为-20.60m·a-1.同期，Fe层的质心高度下降了约230m，变化率为-31.36m·a-1，Fe层RMS宽度则有所增大，变化率为21.01m·a-1. 

Structures and Interannual Variations of the Nocturnal Mesospheric Na and Fe Layers at 30°N

By analyzing the observational data of the Wuhan University Na and Fe lidars from January 2004 to December 2011, the average characteristics, nighttime and seasonal variations of the mesospheric Na and Fe layers at 30°N are obtained. The average centroid height of the Na layer is 91.36km, while the average RMS (root-mean-square) width is 4.64km. The corresponding results for the Fe layer are respectively 88.99 and 4.57km. Considering the influence of the nighttime and seasonal changes of the Na and Fe layers, we extract the interannual changes of the Na and Fe layers. It is found that both the Na and Fe layers are relatively stable during this period. The centroid height of the Na layer decreases by about 58m in the nearly eight years with an annual change rate of -7.91m, and the RMS width of Na layer decreases by about 151m with an change rate of -20.60m·a-1. Meanwhile the centroid height of the Fe layer has a decrease of about 230m with an annual change rate of -31.36m·a-1, and the RMS width of the Fe layer show an increases with an annual change rate of 21.01m·a-1. In addition, the factors that affect the interannual variation of the metal layer were analyzed, and the similarities and differences between the Na layer and the Fe layer were drawn. Based on our research, it is estimated that the atmospheric temperature in the MLT region over Wuhan has a cooling trend closed to pre decade 0.85K.