scholarly journals Accuracy issues of the existing thermospheric wind models: can we rely on them in seeking solutions to wind-driven problems?

2009 ◽  
Vol 27 (6) ◽  
pp. 2277-2284 ◽  
Author(s):  
M. F. Larsen ◽  
C. G. Fesen
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Lower Thermosphere ◽  
Lower Boundary ◽  
Circulation Model ◽  
Horizontal Wind ◽  
Wind Model ◽  
Model Predictions ◽  
Statistical Sense ◽  
Wind Profiles

Abstract. We address the question of the ability of empirical and general circulation model neutral wind profiles in the lower thermosphere to reproduce the observed characteristics of the winds in that part of the atmosphere. The winds in that altitude range are critical for electrodynamic processes, but evaluations of the model winds are generally difficult because of the sparse observational data, which makes an evaluation of the wind predictions over large areas difficult or impossible. In this paper, we use a recently identified characteristic of the winds in the lower thermosphere, namely the enhanced winds and strong shears between 95 and 115 km altitude, as a test of the models, at least in a statistical sense. Our results show that the Horizontal Wind Model (HWM) significantly underestimates the maximum winds and shears in the lower thermosphere, although it has reasonable agreement with the average winds. The NCAR general circulation model used in this study also underestimates the maximum winds and shears significantly when run with standard resolution, as well as producing an unrealistic increase of the wind speed with height. The agreement between the model and the observations improves significantly however, in a statistical sense, when the altitude resolution is increased. The improved height resolution in the model appears to produce a greater improvement in the model predictions than any of the other factors that we examined, such as improving the geomagnetic forcing or the forcing at the lower boundary.

scholarly journals A study into the effect of the diurnal tide on the structure of the background mesosphere and thermosphere using the new coupled middle atmosphere and thermosphere (CMAT) general circulation model

2002 ◽  
Vol 20 (2) ◽  
pp. 225-235 ◽  
Author(s):  
M. J. Harris ◽  
N. F. Arnold ◽  
A. D. Aylward
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atomic Oxygen ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Lower Boundary ◽  
Circulation Model ◽  
Diurnal Tide ◽  
Temperature Structure ◽  
The Mean

Abstract. A new coupled middle atmosphere and thermosphere general circulation model has been developed, and some first results are presented. An investigation into the effects of the diurnal tide upon the mean composition, dynamics and energetics was carried out for equinox conditions. Previous studies have shown that tides deplete mean atomic oxygen in the upper mesosphere-lower thermosphere due to an increased recombination in the tidal displaced air parcels. The model runs presented suggest that the mean residual circulation associated with the tidal dissipation also plays an important role. Stronger lower boundary tidal forcing was seen to increase the equatorial local diurnal maximum of atomic oxygen and the associated 0(1S) 557.7 nm green line volume emission rates. The changes in the mean background temperature structure were found to correspond to changes in the mean circulation and exothermic chemical heating.Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry) Meterology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals Bayesian calibration of the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM)

2009 ◽  
Vol 2 (2) ◽  
pp. 137-144 ◽  
Author(s):  
S. Guillas ◽  
J. Rougier ◽  
A. Maute ◽  
A. D. Richmond ◽  
C. D. Linkletter
Keyword(s):  
Electron Density ◽  
General Circulation Model ◽  
General Circulation ◽  
Lower Boundary ◽  
Circulation Model ◽  
Computer Simulation Model ◽  
Data Types ◽  
Night Time ◽  
Pressure Surface ◽  
Calibration Parameters

Abstract. In this paper, we demonstrate a procedure for calibrating a complex computer simulation model having uncertain inputs and internal parameters, with application to the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). We compare simulated magnetic perturbations with observations at two ground locations for various combinations of calibration parameters. These calibration parameters are: the amplitude of the semidiurnal tidal perturbation in the height of a constant-pressure surface at the TIE-GCM lower boundary, the local time at which this maximises and the minimum night-time electron density. A fully Bayesian approach, that describes correlations in time and in the calibration input space is implemented. A Markov Chain Monte Carlo (MCMC) approach leads to potential optimal values for the amplitude and phase (within the limitations of the selected data and calibration parameters) but not for the minimum night-time electron density. The procedure can be extended to include additional data types and calibration parameters.

scholarly journals Effects of the planetary waves on the MLT airglow

2017 ◽  
Vol 35 (5) ◽  
pp. 1023-1032 ◽  
Author(s):  
Fabio Egito ◽  
Hisao Takahashi ◽  
Yasunobu Miyoshi
Keyword(s):  
General Circulation ◽  
Atomic Oxygen ◽  
Lower Thermosphere ◽  
Lower Boundary ◽  
Circulation Model ◽  
Vertical Transport ◽  
Transport Processes ◽  
Planetary Waves ◽  
Emission Rates ◽  
Middle Latitudes

Abstract. The planetary-wave-induced airglow variability in the mesosphere and lower thermosphere (MLT) is investigated using simulations with the general circulation model (GCM) of Kyushu University. The model capabilities enable us to simulate the MLT OI557.7 nm, O2b(0–1), and OH(6–2) emissions. The simulations were performed for the lower-boundary meteorological conditions of 2005. The spectral analysis reveals that at middle latitudes, oscillations of the emission rates with the period of 2–20 days appear throughout the year. The 2-day oscillations are prominent in the summer and the 5-, 10-, and 16-day oscillations dominate from the autumn to spring equinoxes. The maximal amplitude of the variations induced by the planetary waves was 34 % in OI557.7 nm, 17 % in O2b(0–1), and 8 % in OH(6–2). The results were compared to those observed in the middle latitudes. The GCM simulations also enabled us to investigate vertical transport processes and their effects on the emission layers. The vertical transport of atomic oxygen exhibits similar periodic variations to those observed in the emission layers induced by the planetary waves. The results also show that the vertical advection of atomic oxygen due to the wave motion is an important factor in the signatures of the planetary waves in the emission rates.

Use of weather types to disaggregate general circulation model predictions

1992 ◽  
Vol 97 (D3) ◽  
pp. 2781 ◽  
Author(s):  
Lauren E. Hay ◽  
Gregory J. McCabe ◽  
David M. Wolock ◽  
Mark A. Ayers
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Weather Types ◽  
Model Predictions

Validation of multi-static meteor radar analysis using realistic mesospheric dynamics from UA-ICON model: Reliability of gradients and vertical velocities

2021 ◽  
Author(s):  
Harikrishnan Charuvil Asokan ◽  
Jorge Luis Chau ◽  
Juan Federico Conte ◽  
Gerd Baumgarten ◽  
Juha Vierinen ◽  
...  
Keyword(s):  
Spread Spectrum ◽  
General Circulation ◽  
Lower Thermosphere ◽  
Circulation Model ◽  
Horizontal Wind ◽  
Meteor Radar ◽  
Wind Fields ◽  
Network Systems ◽  
Mlt Dynamics ◽  
Static Approach

<p>Specular meteor radars (SMRs) are a major ground-based instrument to study the mesosphere and the lower thermosphere (MLT) dynamics. The recently developed multi-static approach of SMRs allows maximising the number of measurements from different viewing angles, hence enabling the estimation of horizontal wind fields and their second-order statistics (power spectrum, momentum fluxes). We have installed the operational versions of these techniques in Germany, Peru and Argentina, called SIMONe (Spread-spectrum Interferometric Multistatic meteor radar Observing Network) systems. Here, we present a validation study of multi-static meteor radar analysis by using virtual radar systems on the upper-atmosphere extension of the ICOsahedral Non-hydrostatic (UA-ICON) general circulation model with a horizontal grid spacing of 5 km. This particular study is focusing on the estimates of gradients and vertical velocities with these multi-static systems.</p>

INM RAS coupled atmosphere–ionosphere general circulation model INMAIM (0–130 km)

2018 ◽  
Vol 33 (6) ◽  
pp. 351-357 ◽  
Author(s):  
Dmitry V. Kulyamin ◽  
Evgenii M. Volodin
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Plasma Chemistry ◽  
Lower Ionosphere ◽  
Circulation Model ◽  
Radiative Processes ◽  
Mesosphere And Lower Thermosphere ◽  
Climatic Characteristics

Abstract The paper presents a new INM RAS atmospheric general circulation model, which includes troposphere, stratosphere, mesosphere, and the lower thermosphere, as well as the lower ionospheric regions (INMAIM). Based on the atmospheric part of the INM climatic model INMCM, a new general circulation model was created by adding the middle atmosphere and lower ionosphere description up to 130 km altitudes. A new computational unit for radiative processes calculation was developed for this purpose. For the lower ionosphere a separate plasma chemistry local model was created. The identification of the INMAIM model climate in the mesosphere and lower thermosphere was carried out based on climatological observations. It was shown that model reproduces the general climatic characteristics considerably well.

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