First report of sporadic K layers and comparison with sporadic Na layers at Beijing, China (40.6°N, 116.2°E)

Abstract

A double-laser beam lidar was successfully developed to simultaneously measure K and Na layers at Beijing (40.6°N, 116.2°E) in 2010. Statistical analysis of the parameters of sporadic K (Ks) and sporadic Na (Nas) layers was performed over 2 years of lidar data, and different characteristics of them were found. The average Ks occurrence (2.9%) was lower than that of Nas (5.9%); the Nas occurrence had a maximum (19.3%) in May-June months and a minimum (1.6%) in January-February months, while the Ks occurrence had a maximum (4.9%) in January-February months and a minimum (1.0%) in September-October months; most Ks peaks tended to occur around 93 km, which was ~2 km lower than that of Nas (~95 km); the Ks peak density was often at least 1 order of magnitude lower than that of Nas; notably, two Ks with high peak densities (>1000 cm-3) were observed, which were much higher than K density (15-300 cm-3) reported before. The ascending time of Ks was often longer than its descending time, but an opposite trend occurred for Nas. During the 152 cases of joint observation for the K and Na layers, 21% (32/152) were cases in which Ks and Nas events simultaneously occurred, while 79% (120/152) were cases in which only one layer (K or Na) exhibited a strong Ks or Nas.