Noctilucent clouds and thermospheric dust: Their diffusion and height distribution

Chapman, Sydney; Kendall, P.C.

doi:10.1002/qj.49709138802

Cited by 25 publications

(3 citation statements)

References 26 publications

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“…Due to its mass the proposed spherical ice particle will own a sedimentation velocity w s which depends on the radius of the ice particle, and density and temperature of the surrounding air where g = 9.55 m/s 2 is the gravitational acceleration, m atm = 4.845 · 10 −26 kg is the average mass of an air molecule, and n atm denotes the number density of air (1/m 3 ). The above formula of the fall speed is a derivation by Chapman and Kendall [1965] and Reid [1975]. Later Turco et al [1982] introduced a correction factor of 8/(8 + π) accounting for inelastic collisions which decrease the fall speed by a factor of about 0.7.…”

Section: Model Descriptionmentioning

confidence: 99%

Icy particles in the summer mesopause region: Three‐dimensional modeling of their environment and two‐dimensional modeling of their transport

2002

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[1] In summertime, layers of icy particles form in the high-latitude mesopause region, causing the phenomena of noctilucent clouds and polar mesosphere summer echoes. We study the formation of these layers by means of a 3-D general circulation model of the middle atmosphere (COMMA/IAP) including new modules for the mesospheric chemistry and for the microphysics of icy particles. We initialize the mesopause region with an ensemble of two million particles and investigate their time-dependent transport in a 2-D Lagrangian way. We use the model to study in considerable detail ice particle formation by heterogeneous nucleation on smoke particles, freeze-drying of the mesopause region by formation of ice particles, and the influences of tidal waves and particle eddy diffusion on ice particle and noctilucent cloud (NLC) layer behavior. We present model results on the requirements for adequate size of smoke particles to act as condensation nuclei in the mesopause region (directly after initialization > 0.7 nm radius; after 8 hours > 2 nm), the types of ice particle trajectories, the timescale for growth of particles (6 to 8 hours to radii > 20 nm) and sublimation of ice particles (duration of sublimation phase typically 6 hours), the typical altitude range of maximum NLC brightness (82.5-83.0 km), the size distributions of ice particles (closer to Gaussian than lognormal in shape), the importance of the vertical component of the tidal winds on NLC layer behavior, and the dominance of semidiurnal over diurnal tidal effects. Furthermore, the model allows us to make predictions on a number of NLC features that are either currently under study or may become observable in the near future, such as properties of NLC at high arctic latitudes, and the development of layers with strongly enhanced water vapor mixing ratios near the lower border of the NLCs. (3334); 3332 Meteorology and Atmospheric Dynamics: Mesospheric dynamics; KEYWORDS: Lagrangian transport, diffusion, ice particle, mesopause, NLC, mesospheric tides Citation: Berger, U., and U. von Zahn, Icy particles in the summer mesopause region: Three-dimensional modeling of their environment and two-dimensional modeling of their transport,

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Section: Model Descriptionmentioning

confidence: 99%

Icy particles in the summer mesopause region: Three‐dimensional modeling of their environment and two‐dimensional modeling of their transport

2002

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“…This has been related to decreasing mesopause temperature and increasing mesospheric water vapor concentration possibly caused by the rising level of mesospheric CO 2 and CH 4 , respectively [ Thomas , 1996]. The idea that PMC/NLC particles are composed of water ice was first suggested by Humphreys [1933], then later taken up by Hesstvedt [1961, 1962], Chapman and Kendall [1965], Charlson [1965, 1966], Reid [1975], and Gadsden [1981]. More comprehensive models including microphysics of ice formation were developed by Turco et al [1982], Jensen and Thomas [1988, 1994], Jensen et al [1989], Thomas [1996], and Klostermeyer [1998, 2001].…”

Section: Introductionmentioning

confidence: 99%

Lidar studies of interannual, seasonal, and diurnal variations of polar mesospheric clouds at the South Pole

2003

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[1] Polar mesospheric clouds (PMC) were observed by an Fe Boltzmann temperature lidar at the South Pole in the 1999-2000 and 2000-2001 austral summer seasons. We report the study of interannual, seasonal, and diurnal variations of PMC using more than 430 h of PMC data. The most significant differences between the two seasons are that in the 2000-2001 season, the PMC mean total backscatter coefficient is 82% larger and the mean centroid altitude is 0.83 km lower than PMC in the 1999-2000 season. Clear seasonal trends in PMC altitudes were observed at the South Pole where maximum altitudes occurred around 10-20 days after summer solstice. Seasonal variations of PMC backscatter coefficient and occurrence probability show maxima around 25-40 days after summer solstice. Strong diurnal and semidiurnal variations in PMC backscatter coefficient and centroid altitude were observed at the South Pole with both in-phase and out-of-phase correlations during different years. A significant hemispheric difference in PMC altitudes was found, that the mean PMC altitude of 85.03 km at the South Pole is about 2-3 km higher than PMC in the northern hemisphere. Through comparisons with the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM), the hemispheric difference in PMC altitude is attributed to the hemispheric differences in the altitudes of supersaturation region and in the upwelling vertical wind, which are mainly caused by different solar forcing in two hemispheres that the solar flux in January is 6% greater than the solar flux in July due to the Earth's orbital eccentricity. Gravity wave forcing also contributes to these differences.

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“…Much study is currently being directed towards the relationships between lunar synodical phases and meteor showers (Adderley and Bowen, 1962;Bowen, 1963) , extraterrestrial ice nuclei sources (Bigg andMiles, 1963, 1964) and other lunar influenced meteorological phenomena (Brierley and Davies, 1963;Brier and Bradley, 1964;Lund, 1965). Studies of particles collected by rockets from high altitude noctilucent clouds (Hemenway and Soberman, 1962;Chapman and Kendall, 1965), which normally only appear in the summer, show small diameter (2 f.L) black spherules to be present.…”

Section: Stratigraphic Variabilitymentioning

confidence: 99%

125 : Stratigraphic Analysis of a Deep Ice Core from Greenland

Langway¹

1970

Geological Society of America Special Papers

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Noctilucent clouds and thermospheric dust: Their diffusion and height distribution

Cited by 25 publications

References 26 publications

Icy particles in the summer mesopause region: Three‐dimensional modeling of their environment and two‐dimensional modeling of their transport

Icy particles in the summer mesopause region: Three‐dimensional modeling of their environment and two‐dimensional modeling of their transport

Lidar studies of interannual, seasonal, and diurnal variations of polar mesospheric clouds at the South Pole

125 : Stratigraphic Analysis of a Deep Ice Core from Greenland

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