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 (K_s) and sporadic Na (Nas) layers was performed over 2 years of lidar data, and different characteristics of them were found. The average K_s 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 K_s occurrence had a maximum (4.9%) in January–February months and a minimum (1.0%) in September–October months; most K_s peaks tended to occur around 93 km, which was ~2 km lower than that of Nas (~95 km); the K_s peak density was often at least 1 order of magnitude lower than that of Nas; notably, two K_s 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 K_s 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 K_s and Nas events simultaneously occurred, while 79% (120/152) were cases in which only one layer (K or Na) exhibited a strong K_s or Nas.

We report a world record of lidar profiling of metallic Ca⁺ ions up to 300 km in the midlatitude nighttime ionosphere during geomagnetic quiet time. Ca⁺ measurements (∼80–300 km) were made over Beijing (40.42°N, 116.02°E) with an Optical‐Parametric‐Oscillator‐based lidar from March 2020 through June 2021. Main Ca⁺ layers (80–100 km) persist through all nights, and high‐density sporadic Ca⁺ layers (∼100–120 km) frequently occur in summer. Thermosphere‐ionosphere Ca⁺ (TICa⁺) layers (∼110–300 km) are likely formed via Ca⁺ uplifting from these sporadic layers. The lidar observations capture the complete evolution of TICa⁺ layers from onset to ending, revealing intriguing features. Concurrent ionosonde measurements show strong sporadic E layers developed before TICa⁺ and spread F onset. Neutral winds can partially account for observed vertical transport but enhanced electric fields are required to explain the results. Such lidar observations promise new insights into E‐ and F‐region coupling and plasma inhomogeneities.

A dual‐wavelength resonance fluorescence lidar facility, operating at 341 and 589 nm, was used to observe simultaneously the Ni and Na layers in the upper atmosphere over Yanqing station, Beijing (40.41°N, 116.01°E). Lidar measurements were performed on 126 nights (1090 hr in total) from April 2019 to March 2020 and April 2021 to August 2021, so that the full seasonal cycle of the Ni layer was observed for the first time. The Ni and Na layers exhibit a similar annual cycle, increasing by a factor of ∼3 from a mid‐summer minimum to a midwinter maximum. The annual mean column densities of Ni and Na are 3.1 × 10⁸ and 2.5 × 10⁹ cm⁻², respectively, giving a mean Na:Ni ratio of 8.1, which is significantly larger than their CI chondritic ratio of 1.2. This is explained by the more efficient ablation of Na from cosmic dust particles by a factor of 3, and the more rapid neutralization of Na⁺ between 90 and 100 km, where the measured Na⁺:Ni⁺ ratio is only 2.2. The Ni layer peak occurs around 84 km, 8 km below that of Na. These features are simulated satisfactorily by the Whole Atmosphere Community Climate Model (WACCM) and are explained by significant differences in the neutral chemistry of the two metals below 90 km and their ion‐molecule chemistry between 90 and 100 km.

We report an all-solid-state narrowband lidar system for the simultaneous detection of Ca and Ca⁺ layers over Yanqing (40.41°N, 116.01°E). The uniqueness of this lidar lies in its transmitter, which is based on optical parametric oscillation (OPO) and optical parametric amplification (OPA) techniques. The injection seeded OPO and the OPA are pumped by the second harmonic of an injection-seeded Nd:YAG laser, which can generate coherent light at the wavelength of 786 nm or 846 nm lasers, whose second harmonics in turn generate the 393 nm or 423 nm pulses, respectively, for the detection of thermospheric and ionospheric Ca⁺ and Ca layers. Compared to the conventional dye-based system, this lidar transmitter is a narrowband system (bandwidth < 200 MHz), which has produced a factor of two more output power with higher stability and reliability. The lidar system in Yingqing demonstrated Ca⁺ detection sensitivity of 0.1 atoms-cm⁻³ for long-term observation and reached a height of ~300 km. Potential applications and further improvements in this lidar technique are also discussed in this paper.

We report the first simultaneous lidar observations of thermosphere‐ionosphere sporadic nickel and Na (TISNi and TISNa) layers in altitudes ∼105–120 km over Yanqing (40.42°N, 116.02°E), Beijing. From two years of data spanning April 2019 to April 2020 and July 2020 to June 2021, TISNi layers in May and June possess high densities with a maximum of 818 cm⁻³ on 17 May 2021, exceeding the density of main layer peak (∼85 km) by ∼4 times. They correlate with strong sporadic E layers observed nearby. TISNa layers occur at similar altitudes as TISNi with spatial‐temporal correlation coefficients of ∼1. The enrichment of Ni in TISNi is evident as the [TISNi]/[TISNa] column abundance ratios are ∼1, about 10 times the main layer [Ni]/[Na] ratios. These results are largely explained by neutralization of converged Ni⁺ and Na⁺ ions via recombination with electrons. Calculations show direct recombination dominating over dissociative recombination above ∼105 km.