Characteristics of double sodium layer over Haikou, China (20.0° N, 110.1° E)

We study the property of double sodium layer structures (DSLs) in the mesosphere and lower thermosphere (MLT) by a lidar at the low-latitude location of Haikou (20.0° N, 110.1° E), China. From April 2010 to December 2013, 21 DSLs were observed within a total of 377 observation days. DSLs were recorded at middle latitudes of Beijing and Wuhan, China, but were rarely observed at low latitudes. We analyze and discuss characteristics of DSLs such as time of occurrence, peak altitude, FWHM, duration time, etc. At the same time, the critical frequency f oEs and the virtual height h' Es of the sporadic E layer Es were observed by an ionosonde over Danzhou (19.0° N, 109.3° E). We discuss such their characteristics as differences of time, differences of altitude compared to DSLs. We used an Nd:YAG laser pumped dye laser to generate the probing beam. The wavelength of the dye laser was set to 589 nm by a sodium fluorescence cell. The backscattered fluorescence photons from the sodium layer were collected by a telescope with the Φ1000 mm primary mirror.