Sporadic sodium layers(SSLs)were studied with sodium(Na)lidar at Beijing(40.5°N,116.0°E)and Haikou(19.5°N,109.1°E)in China.The altitude distribution,strength factors,and occurrence time of SSL and sporadic E(Es)layer events were statistically analyzed at both observing sites.SSL occurrence had a maximum near22:00 local time,and Eslayer occurrence had a maximum before midnight.The altitude distributions of SSL and Es layer events were better correlated at Haikou than at Beijing.All the average values of height and strength factor for SSL and Eslayer events,as well as the average of the maximum frequency that can be reflected by the Eslayer(foEs),at Beijing were higher than those at Haikou.A better correlation between SSL and Eslayer events was also found at Haikou,and the formation of SSLs was considered to likely depend on the seasonal variability of chemical and dynamical processes.
