scholarly journals A new model of meteoric calcium in the mesosphere and lower thermosphere

2018 ◽  
Vol 18 (20) ◽  
pp. 14799-14811 ◽  
Author(s):  
John M. C. Plane ◽  
Wuhu Feng ◽  
Juan Carlos Gómez Martín ◽  
Michael Gerding ◽  
Shikha Raizada
Keyword(s):  
Climate Model ◽  
Lower Thermosphere ◽  
Input Function ◽  
Elemental Abundance ◽  
Rate Theory ◽  
Molecule Reaction ◽  
Statistical Rate Theory ◽  
Meteoric Smoke ◽  
Order Of Magnitude ◽  
Mesosphere And Lower Thermosphere

Abstract. Meteoric ablation produces layers of metal atoms in the mesosphere and lower thermosphere (MLT). It has been known for more than 30 years that the Ca atom layer is depleted by over 2 orders of magnitude compared with Na, despite these elements having nearly the same elemental abundance in chondritic meteorites. In contrast, the Ca+ ion abundance is depleted by less than a factor of 10. To explain these observations, a large database of neutral and ion–molecule reaction kinetics of Ca species, measured over the past decade, was incorporated into the Whole Atmosphere Community Climate Model (WACCM). A new meteoric input function for Ca and Na, derived using a chemical ablation model that has been tested experimentally with a Meteoric Ablation Simulator, shows that Ca ablates almost 1 order of magnitude less efficiently than Na. WACCM-Ca simulates the seasonal Ca layer satisfactorily when compared with lidar observations, but tends to overestimate Ca+ measurements made by rocket mass spectrometry and lidar. A key finding is that CaOH and CaCO3 are very stable reservoir species because they are involved in essentially closed reaction cycles with O2 and O. This has been demonstrated experimentally for CaOH, and in this study for CaCO3 using electronic structure and statistical rate theory. Most of the neutral Ca is therefore locked in these reservoirs, enabling rapid loss through polymerization into meteoric smoke particles, and this explains the extreme depletion of Ca.

scholarly journals A new model of meteoric calcium in the mesosphere and lower thermosphere

2018 ◽  
Author(s):  
John M. C. Plane ◽  
Wuhu Feng ◽  
Juan Carlos Gómez Martín ◽  
Michael Gerding ◽  
Shikha Raizada
Keyword(s):  
Climate Model ◽  
Lower Thermosphere ◽  
Large Data ◽  
Input Function ◽  
Elemental Abundance ◽  
Rate Theory ◽  
Molecule Reaction ◽  
Statistical Rate Theory ◽  
Order Of Magnitude ◽  
Mesosphere And Lower Thermosphere

Abstract. Meteoric ablation produces layers of metal atoms in the mesosphere and lower thermosphere (MLT). It has been known for more than 30 years that the Ca atom layer is depleted by over 2 orders of magnitude compared with Na, despite these elements having essentially the same elemental abundance in chondritic meteorites. In contrast, the Ca+ ion abundance is depleted by less than a factor of 10. To explain these observations, a large data-base of neutral and ion-molecule reaction kinetics of Ca species, measured over the past decade, was incorporated into the Whole Atmosphere Community Climate Model (WACCM). A new meteoric input function for Ca and Na, derived using a chemical ablation model that has been tested experimentally with a Meteoric Ablation Simulator, shows that Ca experiences significant differential ablation, by almost 1 order of magnitude, with respect to Na. WACCM-Ca simulates the seasonal Ca layer satisfactorily when compared with lidar observations, but tends to overestimate Ca+ measurements made by rocket mass spectrometry and lidar. A key finding is that CaOH and CaCO3 are very stable reservoir species because they are involved in essentially closed reaction cycles with O2 and O. This has been demonstrated experimentally for CaOH, and in this study for CaCO3 using electronic structure and statistical rate theory. Most of the neutral Ca is therefore locked in these reservoirs, enabling rapid loss through polymerization into meteoric smoke particles and explaining the extreme depletion of Ca.

scholarly journals A new time-resolved model of the mesospheric Na layer: constraints on the meteor input function

2004 ◽  
Vol 4 (1) ◽  
pp. 39-69 ◽  
Author(s):  
J. M. C. Plane
Keyword(s):  
Diurnal Variation ◽  
Lower Thermosphere ◽  
Eddy Diffusion ◽  
Input Function ◽  
Input Rate ◽  
Time Resolved ◽  
Average Value ◽  
Incoherent Scatter ◽  
Continuity Equations ◽  
Meteoric Smoke

Abstract. A time-resolved model of the Na layer in the mesosphere/lower thermosphere region is described, where the continuity equations for the major sodium species Na, Na+ and NaHCO3 are solved explicity, and the other short-lived species are treated in steady-state. It is shown that the diurnal variation of the Na layer can only be modelled satisfactorily if sodium species are permanently removed below about 85 km, both through the dimerization of NaHCO3 and the uptake of sodium species on meteoric smoke particles that are assumed to have formed from the recondensation of vaporized meteoroids. When the sensitivity of the Na layer to the meteoroid input function is considered, an inconsistent picture emerges. The ratio of the column abundances of Na+ to Na is shown to increase strongly with the average meteoroid velocity, because the Na is injected at higher altitudes. Comparison with a limited set of Na+ measurements indicates that the average meteoroid velocity is probably less than about 25 km s−1, in agreement with velocity estimates from conventional meteor radars, and considerably slower than recent observations made by wide aperture incoherent scatter radars. The Na column abundance is shown to be very sensitive to the meteoroid mass input rate, and to the rate of vertical transport by eddy diffusion. Although the magnitude of the eddy diffusion coefficient in the 80–90 km region is uncertain, there is a consensus between recent models using parameterisations of gravity wave momentum deposition that the average value is less than 3×105 cm2 s−1. This requires that the global meteoric mass input rate is less than about 20 t d−1, which is closest to estimates from incoherent scatter radar observations. Finally, the diurnal variation in the meteoroid input rate only slight perturbs the Na layer, because the residence time of Na in the layer is several days, and diurnal effects are effectively averaged out.

scholarly journals A time-resolved model of the mesospheric Na layer: constraints on the meteor input function

2004 ◽  
Vol 4 (3) ◽  
pp. 627-638 ◽  
Author(s):  
J. M. C. Plane
Keyword(s):  
Diurnal Variation ◽  
Lower Thermosphere ◽  
Eddy Diffusion ◽  
Input Function ◽  
Input Rate ◽  
Time Resolved ◽  
Average Value ◽  
Incoherent Scatter ◽  
Continuity Equations ◽  
Meteoric Smoke

Abstract. A time-resolved model of the Na layer in the mesosphere/lower thermosphere region is described, where the continuity equations for the major sodium species Na, Na+ and NaHCO3 are solved explicity, and the other short-lived species are treated in steady-state. It is shown that the diurnal variation of the Na layer can only be modelled satisfactorily if sodium species are permanently removed below about 85 km, both through the dimerization of NaHCO3 and the uptake of sodium species on meteoric smoke particles that are assumed to have formed from the recondensation of vaporized meteoroids. When the sensitivity of the Na layer to the meteoroid input function is considered, an inconsistent picture emerges. The ratio of the column abundance of Na+ to Na is shown to increase strongly with the average meteoroid velocity, because the Na is injected at higher altitudes. Comparison with a limited set of Na+ measurements indicates that the average meteoroid velocity is probably less than about 25 km s-1, in agreement with velocity estimates from conventional meteor radars, and considerably slower than recent observations made by wide aperture incoherent scatter radars. The Na column abundance is shown to be very sensitive to the meteoroid mass input rate, and to the rate of vertical transport by eddy diffusion. Although the magnitude of the eddy diffusion coefficient in the 80–90 km region is uncertain, there is a consensus between recent models using parameterisations of gravity wave momentum deposition that the average value is less than 3×105 cm2 s-1. This requires that the global meteoric mass input rate is less than about 20 td-1, which is closest to estimates from incoherent scatter radar observations. Finally, the diurnal variation in the meteoroid input rate only slight perturbs the Na layer, because the residence time of Na in the layer is several days, and diurnal effects are effectively averaged out.

The Meteoric Ni Layer in the Upper Atmosphere

2021 ◽  
Author(s):  
John Plane ◽  
Shane Daly ◽  
Wuhu Feng ◽  
Thomas Mangan ◽  
Michael Gerding ◽  
...  
Keyword(s):  
Climate Model ◽  
Photon Emission ◽  
Atmospheric Model ◽  
Input Function ◽  
Metallic Phase ◽  
Photochemical Reactions ◽  
Upper Atmosphere ◽  
Dust Particles ◽  
Rate Theory ◽  
Fast Time

<p>The ablation of cosmic dust particles is a source of metallic vapours in planetary upper atmospheres. Recently, ground-based lidars have made the first observations of a layer of Ni atoms peaking around 86 km in the terrestrial atmosphere (in contrast, the layers of Na and Fe have been observed for several decades).  In order to understand these Ni layer observations, we have developed a new version of the Leeds Chemical Ablation Model (CAMBOD) to include a Ni-Fe-S metallic phase in addition to the bulk silicate phase. The validity of the new model was tested using our laboratory Meteoric Ablation Simulator, where micron-size meteoritic particles were flash heated to temperatures as high as 2700 K to simulate their atmospheric entry, and the ablating Ni atoms monitored by fast time-resolved laser induced fluorescence.</p><p>The first global atmospheric model of Ni (WACCM-Ni) was then developed with three components: the Whole Atmosphere Community Climate Model (WACCM6); a meteoric input function derived by coupling an astronomical model of dust sources in the solar system with CABMOD; and a comprehensive set of neutral, ion-molecule and photochemical reactions pertinent to the chemistry of Ni in the upper atmosphere. The kinetics of these reactions were mostly measured in our laboratory, or else modelled theoretically using ab initio quantum calculations combined with statistical rate theory. WACCM-Ni simulates satisfactorily the observed neutral Ni layer peak height and width, as well as Ni<sup>+</sup> ion measurements from rocket-borne mass spectrometry. The Ni layer is predicted to have a similar seasonal and latitudinal variation as the Fe layer, and its unusually broad bottom-side compared with Fe is caused by the relatively fast NiO + CO → Ni + CO<sub>2</sub> reaction. The quantum yield for photon emission from the reaction between Ni and O<sub>3</sub>, which has been observed in the nightglow from space-based spectrometers, is estimated to be between 6 and 40%.</p>

Error Growth in a Whole Atmosphere Climate Model

2009 ◽  
Vol 66 (1) ◽  
pp. 173-186 ◽  
Author(s):  
H-L. Liu ◽  
F. Sassi ◽  
R. R. Garcia
Keyword(s):  
Gravity Waves ◽  
Growth Rates ◽  
Climate Model ◽  
Initial Conditions ◽  
Lower Thermosphere ◽  
Physical Nature ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Finite Limit ◽  
Mesosphere And Lower Thermosphere

Abstract It has been well established that the atmosphere is chaotic by nature and thus has a finite limit of predictability. The chaotic divergence of initial conditions and the predictability are explored here in the context of the whole atmosphere (from the ground to the thermosphere) using the NCAR Whole Atmosphere Community Climate Model (WACCM). From ensemble WACCM simulations, it is found that the early growth of differences in initial conditions is associated with gravity waves and it becomes apparent first in the upper atmosphere and progresses downward. The differences later become more profound on increasingly larger scales, and the growth rates of the differences change in various atmospheric regions and with seasons—corresponding closely with the strength of planetary waves. For example, in December–February the growth rates are largest in the northern and southern mesosphere and lower thermosphere and in the northern stratosphere, while smallest in the southern stratosphere. The growth rates, on the other hand, are not sensitive to the altitude where the small differences are introduced in the initial conditions or the physical nature of the differences. Furthermore, the growth rates in the middle and upper atmosphere are significantly reduced if the lower atmosphere is regularly reinitialized, and the reduction depends on the frequency and the altitude range of the reinitialization.

scholarly journals Observations of NO in the upper mesosphere and lower thermosphere during ECOMA 2010

2012 ◽  
Vol 30 (11) ◽  
pp. 1611-1621 ◽  
Author(s):  
J. Hedin ◽  
M. Rapp ◽  
M. Khaplanov ◽  
J. Stegman ◽  
G. Witt
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Meteor Shower ◽  
The Other ◽  
Sounding Rocket ◽  
Northern Norway ◽  
Smoke Particles ◽  
Meteoric Smoke ◽  
Mesosphere And Lower Thermosphere ◽  
Main Instrument

Abstract. In December 2010 the last campaign of the German-Norwegian sounding rocket project ECOMA (Existence and Charge state Of Meteoric smoke particles in the middle Atmosphere) was conducted from Andøya Rocket Range in northern Norway (69° N, 16° E) in connection with the Geminid meteor shower. The main instrument on board the rocket payloads was the ECOMA detector for studying meteoric smoke particles (MSPs) by active photoionization and subsequent detection of the produced charges (particles and photoelectrons). In addition to photoionizing MSPs, the energy of the emitted photons from the ECOMA flash-lamp is high enough to also photoionize nitric oxide (NO). Thus, around the peak of the NO layer, at and above the main MSP layer, photoelectrons produced by the photoionization of NO are expected to contribute to, or even dominate above the main MSP-layer, the total measured photoelectron current. Among the other instruments on board was a set of two photometers to study the O2 (b1Σg+−X3Σg

scholarly journals Production and transport mechanisms of NO in the polar upper mesosphere and lower thermosphere in observations and models

2018 ◽  
Vol 18 (12) ◽  
pp. 9075-9089 ◽  
Author(s):  
Koen Hendrickx ◽  
Linda Megner ◽  
Daniel R. Marsh ◽  
Christine Smith-Johnsen
Keyword(s):  
Geomagnetic Activity ◽  
Climate Models ◽  
Climate Model ◽  
Heat Budget ◽  
Lower Thermosphere ◽  
No Production ◽  
Superposed Epoch Analysis ◽  
Mesosphere And Lower Thermosphere ◽  
The Impact ◽  
Mlt Region

Abstract. A reservoir of nitric oxide (NO) in the lower thermosphere efficiently cools the atmosphere after periods of enhanced geomagnetic activity. Transport from this reservoir to the stratosphere within the winter polar vortex allows NO to deplete ozone levels and thereby affect the middle atmospheric heat budget. As more climate models resolve the mesosphere and lower thermosphere (MLT) region, the need for an improved representation of NO-related processes increases. This work presents a detailed comparison of NO in the Antarctic MLT region between observations made by the Solar Occultation for Ice Experiment (SOFIE) instrument on-board the Aeronomy of Ice in the Mesosphere (AIM) satellite and simulations performed by the Whole Atmosphere Community Climate Model with Specified Dynamics (SD-WACCM). We investigate 8 years of SOFIE observations, covering the period 2007–2015, and focus on the Southern Hemisphere (SH), rather than on dynamical variability in the Northern Hemisphere (NH) or a specific geomagnetic perturbed event. The morphology of the simulated NO is in agreement with observations though the long-term mean is too high and the short-term variability is too low in the thermosphere. Number densities are more similar during winter, though the altitude of peak NO density, which reaches between 102 and 106 km in WACCM and between 98 and 104 km in SOFIE, is most separated during winter. Using multiple linear regression (MLR) and superposed epoch analysis (SEA) methods, we investigate how well the NO production and transport are represented in the model. The impact of geomagnetic activity is shown to drive NO variations in the lower thermosphere similarly across both datasets. The dynamical transport from the lower thermosphere into the mesosphere during polar winter is found to agree very well with a descent rate of about 2.2 km day−1 in the 80–110 km region in both datasets. The downward-transported NO fluxes are, however, too low in WACCM, which is likely due to medium energy electrons (MEE) and D-region ion chemistry that are not represented in the model.

scholarly journals Comparison of global datasets of sodium densities in the mesosphere and lower thermosphere from GOMOS, SCIAMACHY and OSIRIS measurements and WACCM model simulations from 2008 to 2012

2017 ◽  
Vol 10 (8) ◽  
pp. 2989-3006 ◽  
Author(s):  
Martin P. Langowski ◽  
Christian von Savigny ◽  
John P. Burrows ◽  
Didier Fussen ◽  
Erin C. M. Dawkins ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Climate Model ◽  
Lower Thermosphere ◽  
Temporal Variations ◽  
Equatorial Region ◽  
Local Times ◽  
Vertical Column ◽  
Model Simulations ◽  
Mesosphere And Lower Thermosphere ◽  
Scanning Imaging

Abstract. During the last decade, several limb sounding satellites have measured the global sodium (Na) number densities in the mesosphere and lower thermosphere (MLT). Datasets are now available from Global Ozone Monitoring by Occultation of Stars (GOMOS), the SCanning Imaging Absorption spectroMeter for Atmospheric CHartography (SCIAMACHY) (both on Envisat) and the Optical Spectrograph and InfraRed Imager System (OSIRIS) (on Odin). Furthermore, global model simulations of the Na layer in the MLT simulated by the Whole Atmosphere Community Climate Model, including the Na species (WACCM-Na), are available. In this paper, we compare these global datasets.The observed and simulated monthly averages of Na vertical column densities agree reasonably well with each other. They show a clear seasonal cycle with a summer minimum most pronounced at the poles. They also show signs of a semi-annual oscillation in the equatorial region. The vertical column densities vary from 0. 5  ×  109 to 7  ×  109 cm−2 near the poles and from 3  ×  109 to 4  ×  109 cm−2 at the Equator. The phase of the seasonal cycle and semi-annual oscillation shows small differences between the Na amounts retrieved from different instruments. The full width at half maximum of the profiles is 10 to 16 km for most latitudes, but significantly smaller in the polar summer. The centroid altitudes of the measured sodium profiles range from 89 to 95 km, whereas the model shows on average 2 to 4 km lower centroid altitudes. This may be explained by the mesopause being 3 km lower in the WACCM simulations than in measurements. Despite this global 2–4 km shift, the model captures well the latitudinal and temporal variations. The variation of the WACCM dataset during the year at different latitudes is similar to the one of the measurements. Furthermore, the differences between the measured profiles with different instruments and therefore different local times (LTs) are also present in the model-simulated profiles. This capturing of latitudinal and temporal variations is also found for the vertical column densities and profile widths.

scholarly journals Radar observations of winds, waves and tides in the mesosphere and lower thermosphere over South Georgia island (54°S, 36°W) and comparison to WACCM simulations

2021 ◽  
Author(s):  
Neil P. Hindley ◽  
Neil Cobbett ◽  
David C. Fritts ◽  
Diego Janchez ◽  
Nicholas J. Mitchell ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Lower Thermosphere ◽  
Neutral Atmosphere ◽  
Residual Circulation ◽  
Radar Observations ◽  
South Georgia ◽  
Global Circulation Models ◽  
Mesosphere And Lower Thermosphere ◽  
The Impact

Abstract. The mesosphere and lower thermosphere (MLT) is a dynamic layer of the earth’s atmosphere. This region marks the interface at which neutral atmosphere dynamics begin to influence the ionosphere and space weather. However, our understanding of this region and our ability to accurately simulate it in global circulation models (GCMs) is limited by a lack of observations, especially in remote locations. To this end, a meteor radar was deployed on the remote mountainous island of South Georgia (54° S, 36° W) in the Southern Ocean from 2016 to 2020. The goal of this study is to use these new measurements to characterise the fundamental dynamics of the MLT above South Georgia including large-scale winds, solar tides, planetary waves (PWs) and mesoscale gravity waves (GWs). We first present an improved method for time-height localisation of radar wind measurements and characterise the large-scale MLT winds. We then explore the amplitudes and phases of the diurnal (24 h), semidiurnal (12 h) and terdiurnal (8 h) solar tides at this latitude. We also explore PW activity and find very large amplitudes up to 30 ms−1 for the quasi-2 day wave in summer and show that the dominant modes of the quasi-5, 10 and 16 day waves are westward W1 and W2. We investigate wind variance due to GWs in the MLT and use a new method to show an east-west tendency of GW variance of up to 20 % during summer and a weaker north-south tendency of 0–5 % during winter. This is contrary to the expected tendency of GW directions in the winter stratosphere below, which is a strong suggestion of secondary GW (2GW) observations in the MLT. Lastly, comparison of radar winds to a climatological Whole Atmosphere Community Climate Model (WACCM) simulation reveals a simulated summertime mesopause and zonal wind shear that occur at altitudes around 10 km lower than observed, and southward winds during winter above 90 km altitude in the model that are not seen in observations. Further, wintertime zonal winds above 85 km altitude are eastward in radar observations but in WACCM they are found to weaken and reverse to westward. Recent studies have linked this discrepancy to the impact of 2GWs on the residual circulation which are not included in WACCM. These measurements therefore provide vital constraints that can guide the development of GCMs as they extend upwards into this important region of the atmosphere.

scholarly journals The influence of surface charge on the coalescence of ice and dust particles in the mesosphere and lower thermosphere

2021 ◽  
Vol 21 (11) ◽  
pp. 8735-8745
Author(s):  
Joshua Baptiste ◽  
Connor Williamson ◽  
John Fox ◽  
Anthony J. Stace ◽  
Muhammad Hassan ◽  
...  
Keyword(s):  
Surface Charge ◽  
Lower Thermosphere ◽  
Coefficient Of Restitution ◽  
Dust Particles ◽  
Opposite Charge ◽  
Smoke Particles ◽  
Meteoric Smoke ◽  
Relative Kinetic ◽  
Mesosphere And Lower Thermosphere ◽  
Small Separation

Abstract. Agglomeration of charged ice and dust particles in the mesosphere and lower thermosphere is studied using a classical electrostatic approach, which is extended to capture the induced polarisation of surface charge. Collision outcomes are predicted whilst varying the particle size, charge, dielectric constant, relative kinetic energy, collision geometry and the coefficient of restitution. In addition to Coulomb forces acting on particles of opposite charge, instances of attraction between particles of the same sign of charge are discussed. These attractive forces are governed by the polarisation of surface charge and can be strong at very small separation distances. In the mesosphere and lower thermosphere, these interactions could also contribute to the formation of stable aggregates and contamination of ice particles through collisions with meteoric smoke particles.

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