The observations were conducted by lidar over Haikou (20°N, 110°E) and Beijing (40°N,116°E) in July 2012. The basic characteristics of the sodium layer density at a low-latitude and mid-latitude location are analyzed by the observations. The double sodium layer events and sporadic layer were observed over Beijing and Haikou. A Nd:YAG laser and a pumped dye laser are used to generate the probing beam. The wavelength of the dye laser is set to be 589 nm by a sodium fluorescence cell. The energy and divergence of the beam are set about 45 mJ and 1 mrad, respectively. The backscattered fluorescence photons from the sodium layer are collected by a telescope with a primary mirror which diameter is equal to 1000 mm. There are 9 events of Sporadic Sodium Layer (SSL) and 1 event of Double Sodium Layer (DSL) occurred in Haikou, and 1 event of SSL and 4 events of DSL occurred in Beijing. The variety and distribution of the sodium density over Beijing and Haikou during the night of July 1, 2012 are compared. A DSL structure was observed and it had lasted 120 min during the night of July 1, 2012 over Haikou, but no DSL structure occurred over Beijing.
