scholarly journals Thermal structure and dynamics of the Martian upper atmosphere at solar minimum from global circulation model simulations

2007 ◽  
Vol 25 (10) ◽  
pp. 2147-2158 ◽  
Author(s):  
T. Moffat-Griffin ◽  
A. D. Aylward ◽  
W. Nicholson
Keyword(s):  
Solar Minimum ◽  
Thermal Structure ◽  
Lower Boundary ◽  
Circulation Model ◽  
Upper Atmosphere ◽  
Small Scale ◽  
Ir Absorption ◽  
Neutral Atmosphere ◽  
Accelerometer Data ◽  
Global Circulation Model

Abstract. Simulations of the Martian upper atmosphere have been produced from a self-consistent three-dimensional numerical model of the Martian thermosphere and ionosphere, called MarTIM. It covers an altitude range of 60 km to the upper thermosphere, usually at least 250 km altitude. A radiation scheme is included that allows the main sources of energy input, EUV/UV and IR absorption by CO2 and CO, to be calculated. CO2, N2 and O are treated as the major gases in MarTIM, and are mutually diffused (though neutral chemistry is ignored). The densities of other species (the minor gases), CO, Ar, O2 and NO, are based on diffusive equilibrium above the turbopause. The ionosphere is calculated from a simple photoionisation and charge exchange routine though in this paper we will only consider the thermal and dynamic structure of the neutral atmosphere at solar minimum conditions. The semi-diurnal (2,2) migrating tide, introduced at MarTIM's lower boundary, affects the dynamics up to 130 km. The Mars Climate Database (Lewis et al., 2001) can be used as a lower boundary in MarTIM. The effect of this is to increase wind speeds in the thermosphere and to produce small-scale structures throughout the thermosphere. Temperature profiles are in good agreement with Pathfinder results. Wind velocities are slightly lower compared to analysis of MGS accelerometer data (Withers, 2003). The novel step-by-step approach of adding in new features to MarTIM has resulted in further understanding of the drivers of the Martian thermosphere.

scholarly journals On the influence of zonal gravity wave distributions on the Southern Hemisphere winter circulation

2017 ◽  
Vol 35 (4) ◽  
pp. 785-798 ◽  
Author(s):  
Friederike Lilienthal ◽  
Christoph Jacobi ◽  
Torsten Schmidt ◽  
Alejandro de la Torre ◽  
Peter Alexander
Keyword(s):  
Gravity Wave ◽  
Southern Hemisphere ◽  
Zonal Wind ◽  
Middle Atmosphere ◽  
Lower Boundary ◽  
Circulation Model ◽  
Global Circulation Model ◽  
Global Circulation ◽  
The Andes ◽  
Hemisphere Winter

Abstract. A mechanistic global circulation model is used to simulate the Southern Hemisphere stratospheric, mesospheric, and lower thermospheric circulation during austral winter. The model includes a gravity wave (GW) parameterization that is initiated by prescribed 2-D fields of GW parameters in the troposphere. These are based on observations of GW potential energy calculated using GPS radio occultations and show enhanced GW activity east of the Andes and around the Antarctic. In order to detect the influence of an observation-based and thus realistic 2-D GW distribution on the middle atmosphere circulation, we perform model experiments with zonal mean and 2-D GW initialization, and additionally with and without forcing of stationary planetary waves (SPWs) at the lower boundary of the model. As a result, we find additional forcing of SPWs in the stratosphere, a weaker zonal wind jet in the mesosphere, cooling of the mesosphere and warming near the mesopause above the jet. SPW wavenumber 1 (SPW1) amplitudes are generally increased by about 10 % when GWs are introduced being longitudinally dependent. However, at the upper part of the zonal wind jet, SPW1 in zonal wind and GW acceleration are out of phase, which reduces the amplitudes there.

scholarly journals Polar heating in Saturn's thermosphere

2005 ◽  
Vol 23 (7) ◽  
pp. 2465-2477 ◽  
Author(s):  
C. G. A. Smith ◽  
A. D. Aylward ◽  
S. Miller ◽  
I. C. F. Müller-Wodarg
Keyword(s):  
Heat Source ◽  
Thermal Structure ◽  
Circulation Model ◽  
Polar Regions ◽  
Global Circulation Model ◽  
Global Circulation ◽  
Total Energy Input ◽  
Planetary Ionosphere ◽  
Thermospheric Dynamics

Abstract. A 3-D numerical global circulation model of the Kronian thermosphere has been used to investigate the influence of polar heating. The distributions of temperature and winds resulting from a general heat source in the polar regions are described. We show that both the total energy input and its vertical distribution are important to the resulting thermal structure. We find that the form of the topside heating profile is particularly important in determining exospheric temperatures. We compare our results to exospheric temperatures from Voyager occultation measurements (Smith et al., 1983; Festou and Atreya, 1982) and auroral H3+ temperatures from ground-based spectroscopic observations (e.g. Miller et al., 2000). We find that a polar heat source is consistent with both the Smith et al. determination of T∞~400 K at ~30° N and auroral temperatures. The required heat source is also consistent with recent estimates of the Joule heating rate at Saturn (Cowley et al., 2004). However, our results show that a polar heat source can probably not explain the Festou and Atreya determination of T∞~800 K at ~4° N and the auroral temperatures simultaneously. Keywords. Ionosphere (Planetary ionosphere) – Magnetospherica physics (Planetary magnetospheres) – Meterology and atmospheric dynamics (Thermospheric dynamics)

scholarly journals Upper atmospheres of terrestrial planets: Carbon dioxide cooling and the Earth’s thermospheric evolution

2018 ◽  
Vol 617 ◽  
pp. A107 ◽  
Author(s):  
C. P. Johnstone ◽  
M. Güdel ◽  
H. Lammer ◽  
K. G. Kislyakova
Keyword(s):  
Chemical Reactions ◽  
Molecular Diffusion ◽  
Thermal Structure ◽  
Lower Boundary ◽  
Upper Atmosphere ◽  
Earth Model ◽  
Chemical Compositions ◽  
Electron Gases ◽  
Ir Radiation ◽  
Chemical Structures

Context.The thermal and chemical structures of the upper atmospheres of planets crucially influence losses to space and must be understood to constrain the effects of losses on atmospheric evolution.Aims.We develop a 1D first-principles hydrodynamic atmosphere model that calculates atmospheric thermal and chemical structures for arbitrary planetary parameters, chemical compositions, and stellar inputs. We apply the model to study the reaction of the Earth’s upper atmosphere to large changes in the CO2abundance and to changes in the input solar XUV field due to the Sun’s activity evolution from 3 Gyr in the past to 2.5 Gyr in the future.Methods.For the thermal atmosphere structure, we considered heating from the absorption of stellar X-ray, UV, and IR radiation, heating from exothermic chemical reactions, electron heating from collisions with non-thermal photoelectrons, Joule heating, cooling from IR emission by several species, thermal conduction, and energy exchanges between the neutral, ion, and electron gases. For the chemical structure, we considered ~500 chemical reactions, including 56 photoreactions, eddy and molecular diffusion, and advection. In addition, we calculated the atmospheric structure by solving the hydrodynamic equations. To solve the equations in our model, we developed the Kompot code and have provided detailed descriptions of the numerical methods used in the appendices.Results.We verify our model by calculating the structures of the upper atmospheres of the modern Earth and Venus. By varying the CO2abundances at the lower boundary (65 km) of our Earth model, we show that the atmospheric thermal structure is significantly altered. Increasing the CO2abundances leads to massive reduction in thermospheric temperature, contraction of the atmosphere, and reductions in the ion densities indicating that CO2can significantly influence atmospheric erosion. Our models for the evolution of the Earth’s upper atmosphere indicate that the thermospheric structure has not changed significantly in the last 2 Gyr and is unlikely to change signficantly in the next few Gyr. The largest changes that we see take place between 3 and 2 Gyr ago, with even larger changes expected at even earlier times.

The Interaction of Ozone Photochemistry and Dynamics in the Stratosphere. A Three-dimensional Atmospheric Model

1974 ◽  
Vol 52 (8) ◽  
pp. 1599-1609 ◽  
Author(s):  
Julius London ◽  
Jae H. Park
Keyword(s):  
General Pattern ◽  
Relaxation Times ◽  
Three Dimensional ◽  
Lower Boundary ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Transport Processes ◽  
Global Circulation Model ◽  
Ozone Distribution ◽  
Ozone Photochemistry

In the stratosphere the relaxation times for transport and ozone photochemistry in an oxygen–hydrogen–nitrogen system are approximately comparable. Therefore, realistic models used to calculate ozone variations need to be based on the interaction of the photochemistry and dynamics in this region.The model used in the present study is the three-dimensional global circulation model developed at the National Center for Atmospheric Research. The photochemical calculations for ozone are carried out as time dependent in a three-dimensional O–H–N system.The dynamic model is started from an atmosphere initially at rest and then spun up to a steady state circulation corresponding to mid-January. An initial observed ozone distribution is added and the model is then run through 30 simulated days. Analysis of the time variation of the ozone distribution shows that photochemistry dominates the ozone changes in the sub-solar middle stratosphere, and transport processes redistribute the ozone poleward and downward into the troposphere. Although the general pattern of ozone changes seem to be correct, the model produces too much ozone in the Southern hemisphere subtropical stratosphere and transports too much ozone into the Northern subtropical troposphere. The computed lower boundary flux of about 5 × 1010 cm−2 s−1 corresponds quite well to estimates given in the literature.

Development of a three-dimensional global circulation model for Uranus

2020 ◽  
Author(s):  
Orkun Temel ◽  
Özgür Karatekin
Keyword(s):  
Thermal Structure ◽  
Three Dimensional ◽  
Circulation Model ◽  
General Purpose ◽  
Heat Fluxes ◽  
Global Circulation Model ◽  
Geophysical Research ◽  
Global Circulation ◽  
Before And After ◽  
Cloud Patterns

<p>In this study, we present the Uranus implementation of the planetWRF model [1]. For the determination of the radiative heat fluxes in our three-dimensional global circulation model, we make use of a simple analytic radiative model. This model is based on two-stream approximation and using a power-law scaling for the relationship between the optical depth and the pressure [2]. Preliminary results are compared to the zonal wind [3] and vertical temperature observations [4]. The effect of model's resolution, both vertical and horizontal, on the representation of the strong zonal transport in the Uranian atmosphere, is investigated. Moreover, we discuss the seasonal wind speed variations predicted by our model, assessing its potential to predict the changes in the zonal transport before and after the equinox in 2007. Possible implications for the Entry, Descent, and Landing applications are also presented. The devleoped GCM can also be potentially applied to the atmosphere of Neptune. </p><p><br>[1] Richardson, Mark I., Anthony D. Toigo, and Claire E. Newman. "PlanetWRF: A general purpose, local to global numerical model for planetary atmospheric and climate dynamics." Journal of Geophysical Research: Planets 112.E9 (2007).<br>[2] Robinson, Tyler D., and David C. Catling. "An analytic radiative-convective model for planetary atmospheres." The Astrophysical Journal 757.1 (2012): 104.<br>[3] L.A. Sromovsky, I. de Pater, P.M. Fry, H.B. Hammel, P. Marcus, High S/N Keck and Gemini AO imaging of Uranus during 2012–2014: new cloud patterns, increasing activity, and improved wind measurements. Icarus 258, 192–223 (2015).<br>[4] Marley, Mark S., and Christopher P. McKay. "Thermal structure of Uranus' atmosphere." Icarus 138.2 (1999): 268-286.</p>

scholarly journals Non-linear statistical downscaling of present and LGM precipitation and temperatures over Europe

2007 ◽  
Vol 3 (4) ◽  
pp. 899-933 ◽  
Author(s):  
M. Vrac ◽  
D. Paillard ◽  
P. Naveau
Keyword(s):  
Statistical Downscaling ◽  
Large Scale ◽  
Western Europe ◽  
Generalized Additive Models ◽  
Circulation Model ◽  
Additive Models ◽  
Future Climate Change ◽  
Small Scale ◽  
Global Circulation Model ◽  
Non Linear

Abstract. The needs of small-scale climate information have become prevalent to study the impacts of future climate change as well as for paleoclimate researches where the reconstructions from proxies are obviously local. In this study we develop a non-linear statistical downscaling method to generate local temperatures and precipitation values from large-scale variables (e.g. Global Circulation Model – GCM – outputs), through Generalized Additive Models (GAMs) calibrated on the present Western Europe climate. First, various monthly GAMs (i.e. one model for each month) are tested for preliminary analysis. Then, annual GAMs (i.e. one model for the 12 months altogether) are developed and tailored for two sets of predictors (geographical and physical) to downscale local temperatures and precipitation. As an evaluation of our approach under large-scale conditions different from present Western Europe, projections are realized (1) for present North America and Northern Europe and compared to local observations (spatial test); and (2) for the Last Glacial Maximum (LGM) period, and compared to local reconstructions and GCMs outputs (temporal test). In general, both spatial and temporal evaluations indicate that the GAMs are flexible and efficient tools to capture and downscale non-linearities between large- and local-scale variables. More precisely, the results emphasize that, while physical predictors alone are not capable of downscaling realistic values when applied to climate strongly different from the one used for calibration, the inclusion of geographical-type variables – such as altitude, advective continentality and W-slope – into GAM predictors brings robustness and improvement to the method and its local projections.

scholarly journals A Comparative Evaluation of a Mesoscale Model and Atmospheric Global Circulation Model for Air Quality Simulation: A Multiscale, Multisite Evaluation

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
P. Goswami ◽  
J. Baruah
Keyword(s):  
High Resolution ◽  
Mesoscale Model ◽  
Large City ◽  
Circulation Model ◽  
Urban Pollution ◽  
Atmospheric Pollutants ◽  
Scale Model ◽  
Global Circulation Model ◽  
Global Circulation ◽  
Meso Scale

Concentrations of atmospheric pollutants are strongly influenced by meteorological parameters like rainfall, relative humidity and wind advection. Thus accurate specifications of the meteorological fields, and their effects on pollutants, are critical requirements for successful modelling of air pollution. In terms of their applications, pollutant concentration models can be used in different ways; in one, short term high resolution forecasts are generated to predict and manage urban pollution. Another application of dynamical pollution models is to generate outlook for a given airbasin, such as over a large city. An important question is application-specific model configuration for the meteorological simulations. While a meso-scale model provides a high-resolution configuration, a global model allows better simulation of large-sale fields through its global environment. Our objective is to comparatively evaluate a meso-scale atmospheric model (MM5) and atmospheric global circulation model (AGCM) in simulating different species of pollutants over different airbasins. In this study we consider four locations: ITO (Central Delhi), Sirifort (South Delhi), Bandra (Mumbai) and Karve Road (Pune). The results show that both the model configurations provide comparable skills in simulation of monthly and annual loads, although the skill of the meso-scale model is somewhat higher, especially at shorter time scales.

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