Average properties and small-scale variations of the mesospheric Na and Fe layers as observed simultaneously by two closely colocated lidars at 30° N

Abstract

Abstract. We report the average properties and small-scale variation features of the mesospheric Na and Fe layers at 30 • N from extensive simultaneous and common-volume Na and Fe lidar measurements at Wuhan, China. The annual mean Na and Fe density profiles are derived in terms of an averaging method taken from an early literature. The mean Na and Fe profiles preserve the sharp gradients present in most individual density profiles near the layer bottom. Near the bottommost of the layers the mean Na and Fe scale heights are respectively −0.42 and −0.30 km. The mean layer parameters coincide well with the previous report. The Na and Fe densities in the lowest several kilometers of the layers consistently exhibit nearly the same time variations. A clearcut distinction between the Na and Fe time variations always appears in an altitude range near 90 km. A relatively weak positive correlation between them persistently occurs also in an altitude range near 100 km. The mean increase and decrease rates for both Na and Fe are altitude dependent and have a single-peak structure. The time constant of the layer variation is ∼0.07-2.0 h for Na and ∼0.02-1.7 h for Fe, suggesting that the variability is dominated by small-scale processes. However, there is also a slow net increase in each of the annual mean column abundances (Na and Fe) during night.

Simultaneous, common‐volume lidar observations and theoretical studies of correlations among Fe/Na layers and temperatures in the mesosphere and lower thermosphere at Boulder Table Mountain (40°N, 105°W), Colorado

“…In other words, the Fe and Na density fluctuations are similar and in phase on the bottomsides and topsides of both layers and similar but 180°out of phase between the layer peaks. This behavior is similar to the observations reported by Chen and Yi [2011].…”

“…[29] The larger gradient at the Fe and Na layer bottomside as compared to the topside has been characterized by Chen and Yi [2011] in great detail. This is also confirmed in our data.…”

Relationship between mesospheric Na and Fe layers from simultaneous and common‐volume lidar observations at Arecibo

“…It is found that both the top and bottom sides of the correlation profiles are positive, while the middle part is negative for all the three nights studied. This is the same as found by Chen and Yi [] over Wuhan, China, which indicates that this relationship may very well exist globally.…”

“…At the same time, the values in the medium height range are negative and can reach −0.5 or less. The positive‐negative‐positive correlation as a function of altitude between Na and Fe is the same as that reported by Chen and Yi [] for lidar observations over Wuhan, China. The regions of negative values are 88.16–89.96, 90.56–93.56, and 90.54–96.24 km, respectively, for 2–3 July, 18–19, and 22–23 December 2003.…”

Simultaneous and common‐volume lidar observations of K/Na layers and temperature at Arecibo Observatory (18°N, 67°W)

“…Yi et al [] found that the lower boundaries of the simultaneously observed Fe and Na followed almost the same track. Chen and Yi [] showed for the first time that the Fe and Na fluctuations are positively correlated on both the bottomside and the topside of the layers, whereas they are typically negatively correlated near 90 km. These features have also been verified by the simultaneous Fe and Na observations at Arecibo Observatory (AO), Puerto Rico (18.35°N, 66.75°W) [ Yue et al ., ] and at Boulder, Colorado (40°N, 105°W) [ Huang et al ., ].…”