Oscillations in polar mesospheric summer echoes and bifurcation of noctilucent cloud formation

Abstract

Oscillations having periods of 5.5 days are found in polar mesospheric summer echoes (PMSEs) observed during 1980 to 1984 with the MST radar at Poker Flat, Alaska. Simulations of noctilucent cloud (NLC) formation are made in the case that embryos for cloud ice particles are proton‐hydrates H+(H2O)n (PHs). Results show that cloud formation bifurcates from a stably steady structure into a quasi‐steady and a stably oscillatory structure in accordance with an increase of humidity. By capturing electrons, descending crowds of ice particles may cause PMSEs. The cyclic behavior of PMSEs is considered to be an indication of the in situ origin of NLCs.

A model study of global variability in mesospheric cloudiness

“…A cyclical behavior of the ice clouds is undoubtedly due to the feedback between ice sedimentation and sublimation, followed by upwelling of the gas phase water vapor back into the cold region. A similar cyclical pattern was discussed by Sugiyama et al (1996). The non-stationary behavior seen here illustrates the difficulty in choosing the proper part of the cloud lifecycle to compare with observations.…”

Ground-based observations of noctilucent clouds with a northern hemisphere network of automatic digital cameras

“…Our data demonstrate that 4-day, 5-day and 6-day time intervals are present in the NLC periodicity. A 5-day period is well-known in NLCs (Gadsden, 1985;Sugiyama et al, 1996;Kirkwood and Stebel, 2003;Merkel et al, 2003) and is usually associated with a free traveling quasi 5-day planetary wave of zonal wave number 1. Note that theoretical considerations (e.g.…”

“…Planetary waves disturb the summer mesosphere temperature (Espy and Witt, 1996) to such a degree that a strong correlation exists between the probability of NLC appearance and the combined effect of stationary, 16-day and 5-day planetary waves (Kirkwood and Stebel, 2003). The 5-day period in NLCs was detected using ground-based observations (Gadsden, 1985;Sugiyama et al, 1996;Kirkwood and Stebel, 2003). The signatures of the 5-day planetary wave were also observed in PMCs from satellite data (Merkel et al, 2003).…”

Modeling the microphysics of mesospheric ice particles: Assessment of current capabilities and basic sensitivities

“…Nanometer-sized smoke particles have traditionally been the 'nuclei of choice', being used in all major model studies with the exception of the studies by Sugiyama (1994) and Sugiyama et al (1996). Originally, it has been proposed that these particles form as a product of meteoroid ablation in the altitude range between 75 and 115 km (Rosinski and Snow, 1961;Hunten et al, 1980).…”