Alexander S. Medvedev

Max Planck Institute for Solar System Research | MPS · Division of Physics of Planets and Comets

This paper presents a contemporary review of vertical coupling in the atmosphere and ionosphere system induced by internal waves of lower atmospheric origin. Atmospheric waves are primarily generated by meteorological processes, possess a broad range of spatial and temporal scales, and can propagate to the upper atmosphere. A brief summary of inter...

On Earth and on other planets, internal gravity waves shape the dynamics and thermodynamics of the atmosphere.

The dynamical and thermodynamical importance of gravity waves was initially recognized in the atmosphere of Earth. Extensive studies over recent decades demonstrated that gravity waves exist in atmospheres of other planets, similarly play a significant role in the vertical coupling of atmospheric layers and, thus, must be included in numerical gene...

Simulations with the Max Planck Institute Martian general circulation model for Martian years 28 and 34 reveal details of the water “pump” mechanism and the role of gravity wave (GW) forcing. Water is advected to the upper atmosphere mainly by upward branches of the meridional circulation: in low latitudes during equinoxes and over the south pole d...

Plain Language Summary Gravity waves are small‐scale fluctuations of air density, temperature, and other atmospheric variables, which are dynamically important in the upper atmospheres. During Cassini's Grand Finale, observations with the Ultraviolet Imaging Spectrograph delivered a set of density profiles in the Saturnian thermosphere with a resol...

Observations of vibrationally excited hydroxyl (OH*) emissions are widely used to obtain information on atmospheric dynamics and composition. In this paper, several analytical approximations are presented for characteristics of the hydroxyl layer in the Martian atmosphere, such as OH* concentrations at the maximum and the height of the maximum. Rel...

Gravity waves are a key mechanism that facilitates coupling between the lower and upper atmosphere of Mars. In order to better understand the mean, large‐scale impacts of gravity waves on the thermosphere, a modern whole atmosphere, nonlinear, non‐orographic gravity wave parameterization scheme has been incorporated into a three‐dimensional ground‐...

Using the horizontal neutral wind observations from the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument onboard NASA's Ionospheric Connection Explorer (ICON) spacecraft with continuous coverage, we determine the climatology of the mean zonal and meridional winds and the associated mean circulation at lo...

Using the horizontal neutral wind observations from the MIGHTI instrument onboard NASA's ICON (Ionospheric Connection Explorer) spacecraft with continuous coverage, we determine the climatology of the mean zonal and meridional winds and the associated mean circulation at low- to middle latitudes ($10^\circ$S-40$^{\circ}$N) for Northern Hemisphere {...

Observations of excited hydroxyl (OH*) emissions are broadly used for inferring information about atmospheric dynamics and composition. We present several analytical approximations for characterizing the excited hydroxyl layer in the Martian atmosphere. They include the OH* number density at the maximum and the height of the peak, along with the re...

Simulations with the Max Planck Institute Martian general circulation model for Martian years 28 and 34 reveal details of the water "pump" mechanism and the role of gravity wave (GW) forcing. Water is advected to the upper atmosphere mainly by upward branches of the meridional circulation: in low latitudes during equinoxes and over the south pole d...

Atmospheric gravity (buoyancy) waves (GWs) are of great importance for the energy and momentum budget of all planetary atmospheres. Propagating upward waves carry energy and momentum from the lower atmosphere to thermospheric altitudes and redistribute them there. On Mars, GWs dominate the variability of the thermosphere and ionosphere. We provide...

The paper presents observations of gravity wave-induced temperature disturbances in the Martian atmosphere obtained with the mid-infrared (MIR) spectrometer, a channel of the Atmospheric Chemistry Suite instrument on board the Trace Gas Orbiter (ACS/TGO). Solar occultation measurements of a CO2 absorption band at 2.7 m were used for retrieving den...

Atmospheric gravity (buoyancy) waves (GWs) are of great importance for the energy and momentum budget of all planetary atmospheres. Propagating upward waves carry energy and momentum from the lower atmosphere to thermospheric altitudes and re-distribute them there. On Mars, GWs dominate the variability of the thermosphere and ionosphere. We provide...

We report on the direct measurements of zonal winds around 80 km altitude during the 2018 planet‐encircling dust event (PEDE) by infrared (IR) heterodyne spectroscopy. The observed Doppler shifts assume intense retrograde (easterly) winds (208 ± 17 m s⁻¹, 159 ± 20 m s⁻¹, 211 ± 20 m s⁻¹ on June 21, June 27, August 31, 2018, respectively) in the equa...

Lower atmospheric global dust storms affect the small- and large-scale weather and variability of the whole Martian atmosphere. Analysis of the CO2 density data from the Neutral Gas and Ion Mass Spectrometer instrument on board NASA's Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft show a remarkable increase of gravity wave (GW)-induced densi...

Atmospheric gravity waves (GWs) are generated in the lower atmosphere by various weather phenomena. They propagate upward, carry energy and momentum to higher altitudes, and appreciably influence the general circulation upon depositing them in the middle and upper atmosphere. We use a three-dimensional first-principle general circulation model (GCM...

Lower atmospheric global dust storms affect the small- and large-scale weather and variability of the whole Martian atmosphere. Analysis of the CO$_2$ density data from the Neutral Gas and Ion Mass Spectrometer instrument (NGIMS) on board NASA's Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft show a remarkable increase of GW-induced density f...

Plain Language Summary Gravity waves (GWs) are oscillations of wind, temperature, pressure, and density that originate in the dense lower atmosphere. They grow in amplitude upon propagation upward and represent a major driving force in the thinner middle and upper atmosphere. GWs are difficult to account for in general circulation models because th...

Atmospheric gravity waves (GWs) are generated globally in the lower atmosphere by various weather phenomena during all seasons. They propagate upward, carry a significant amount of energy and momentum to higher altitudes, and significantly influence the general circulation of the middle and upper atmosphere. We use a three-dimensional first-princip...

The upper atmosphere of Mars is constantly perturbed by small-scale gravity waves propagating from below. As gravity waves strongly affect the large-scale dynamics and thermal state, constraining their statistical characteristics is of great importance for modeling the atmospheric circulation. We present a new data set of density perturbation ampli...

The paper presents results of simulations with a high‐resolution (equivalent to ∼67‐km grid size) Martian general circulation model (MGCM) from the surface up to the mesosphere for a full Martian year. The obtained climatology of the small‐scale disturbances can serve as a proxy for gravity waves (GWs) that are largely not resolved by MGCMs with co...

We present results of simulations with the Max Planck Institute Martian general circulation model implementing a hydrological cycle scheme. The simulations reveal a seasonal water “pump” mechanism responsible for the upward transport of water vapor. This mechanism occurs in high latitudes above 60° of the southern hemisphere at perihelion, when the...

We present results of simulations with the Max Planck Institute general circulation model (MPI-MGCM) implementing a hydrological cycle scheme. The simulations reveal a seasonal water "pump" mechanism responsible for the upward transport of water vapor. This mechanism occurs in high latitudes above 60$^\circ$ of the southern hemisphere at perihelion...

Carbon dioxide (CO2) ice clouds have been routinely observed in the middle atmosphere of Mars. However, there are still uncertainties concerning physical mechanisms that control their altitude, geographical, and seasonal distributions. Using the Max Planck Institute Martian General Circulation Model (MPI-MGCM), incorporating a state-of-the-art whol...

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital paramete...

Carbon dioxide (CO2) ice clouds have been routinely observed in the middle atmosphere of Mars. However, there are still uncertainties concerning physical mechanisms that control their altitude, geographical, and seasonal distributions. Using the Max Planck Institute Martian General Circulation Model (MPI-MGCM), incorporating a state-of-the-art whol...

Density measurements from the MAVEN orbiter provide information for explaining the physics of the thermosphere. MPI Martian General Circulation Model (known as MAOAM MGCM) is used for interpretation of the MAVEN data. The study reveals and constrains the effects in the thermosphere of internal gravity waves generated in the lower atmosphere. Simula...

Observations of the Mars upper atmosphere made from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft have been used to determine the loss rates of gas from the upper atmosphere to space for a complete Mars year (16 Nov 2014 – 3 Oct 2016). Loss rates for H and O are sufficient to remove ∼2-3 kg/s to space. By itself, this loss would be...

We present a new implementation of the hydrological cycle scheme into a general circulation model of the Martian atmosphere. The model includes a semi-Lagrangian transport scheme for water vapor and ice, and accounts for microphysics of phase transitions between them. The hydrological scheme includes processes of saturation, nucleation, particle gr...

We present a new implementation of the hydrological cycle scheme into a general circulation model of the Martian atmosphere. The model includes a semi-Lagrangian transport scheme for water vapor and ice and accounts for microphysics of phase transitions between them. The hydrological scheme includes processes of saturation, nucleation, particle gro...

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to...

Motions of neutrals and ions in the thermosphere-ionosphere (TI) do not, generally, coincide due to the presence of the geomagnetic field and associated electromagnetic forces affecting plasma. Collisions of ions with gravity wave (GW)-induced motions of neutrals impose damping on the latter. We derive a practical formula for the vertical damping r...

For the first time, the direct effects of lower atmospheric small-scale gravity waves (GWs) on the diurnal migrating tide have been studied from the mesosphere to the upper thermosphere. For this, a general circulation model that account for the whole atmosphere GW parameterization of Yiğit et al. [2008] has been used to account for direct GW propa...

Effects of subgrid-scale gravity waves (GWs) on the diurnal migrating tides are investigated from the mesosphere to the upper thermosphere for September equinox conditions, using a general circulation model coupled with the extended spectral nonlinear GW parameterization of Yiğit et al. [2008].. Simulations with GW effects cut-off above the turbopa...

Wavelike perturbations in the Martian upper thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the MAVEN spacecraft have been analyzed. The amplitudes of small-scale perturbations with apparent wavelengths between ~100 and ~500 km in the Ar density around the exobase show a clear dependence on temperature (T0) of the upp...

Results of simulations with a new high-resolution Martian general circulation model (MGCM) (T106 spectral resolution, or ~67-km horizontal grid size) have been analyzed to reveal global distributions of gravity waves (GWs) during the solstice and equinox periods. They show that shorter-scale harmonics progressively dominate with height, and the bod...

Gravity waves are primarily generated in the lower atmosphere, and can reach thermospheric heights in the course of their propagation. This paper reviews the recent progress in understanding the role of gravity waves in vertical coupling during sudden stratospheric warmings. Modeling of gravity wave e ects is brie y reviewed, and the recent develop...

Newly released Imaging Ultraviolet Spectrograph/Mars Atmosphere and Volatile EvolutioN (IUVS/MAVEN) measurements of CO2 density in the Martian thermosphere have been used for comparison with the predictions of the Max Planck Institute Martian General Circulation Model (MPI-MGCM). The simulations reproduced (within one standard deviation) the availa...

Within the numerical general-circulation model of the Martian atmosphere MAOAM (Martian Atmosphere: Observation and Modeling), we have developed the water cycle block, which is an essential component of modern general circulation models of the Martian atmosphere. The MAOAM model has a spectral dynamic core and successfully predicts the temperature...

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are plane...

The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune—all unknown in the Solar System. Observations to date have shown that ou...

First high-altitude observations of gravity wave (GW)-induced CO2 density perturbations in the Martian thermosphere retrieved from NASA’s Neutral Gas Ion Mass Spectrometer (NGIMS) instrument on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite are presented and interpreted using the extended GW parameterization of Yi ˘ git et al. (...

Global characteristics of the small-scale gravity wave (GW) field in the Martian atmosphere obtained from a high-resolution general circulation model (GCM) are presented for the first time. The simulated GW-induced temperature variances are in a good agreement with available radio occultation data in the lower atmosphere between 10 and 30 km. The m...

First high-altitude observations of gravity wave (GW)-induced CO$_2$ density perturbations in the Martian thermosphere retrieved from NASA's NGIMS instrument on board the MAVEN satellite are presented and interpreted using the extended GW parameterization of Yi\u{g}it et al. [2008] and the Mars Climate Database as an input. Observed relative densit...

We present the first general circulation model simulations that quantify and reproduce patches of extremely cold air required for CO$_2$ condensation and cloud formation in the Martian mesosphere. They are created by subgrid-scale gravity waves (GWs) accounted for in the model with the interactively implemented spectral parameterization. Distributi...

Observations show that the lower thermosphere of Mars ($\sim$100--140 km) is up to 40 K colder than the current general circulation models (GCMs) can reproduce. Possible candidates for physical processes missing in the models are larger abundances of atomic oxygen facilitating stronger CO$_2$ radiative cooling, and thermal effects of gravity waves....

We present the results of the first investigation of the influence of small-scale gravity waves (GWs) originating in the lower atmosphere on the variability of the high-latitude thermosphere during a sudden stratospheric warming (SSW). We use a general circulation model that incorporates the spectral GW parameterization of Yiğit et al. (2008). Duri...

[1] Simulations with a general circulation model (GCM) have been performed to study the Martian upper atmosphere during two major dust storms. The GCM extending from the surface to about 160 km included a spectral parameterization of subgrid-scale gravity waves suitable for planetary thermospheres, and prescribed four-dimensional dust distributions...

1] The formation of CO 2 ice clouds in the northern winter polar atmosphere of Mars and their relation to baroclinic planetary waves, which dominate local dynamics, are studied using a general circulation model. The simulation shows that clouds are formed at altitudes of up to 40 km, and their occurrence correlates to a large degree with the cold p...

CO2 snow forms in the high-latitude atmosphere of Mars in regular patches coinciding with passages of baroclinic planetary waves (periodic oscillations of temperature and other meteorological fields). Our simulations using a Mars general circulation model (MGCM) show that about a half of the snow cover on the northern polar cap is created by such s...

Dust suspended in the martian atmosphere strongly affects the radiative transfer. Diabatic heating and cooling it creates are prominent factors that drive the atmosphere at various scales. This paper provides a review of dust influence on the large-scale dynamics in the atmosphere of Mars above approximately 10 km. We outline the established proper...

Global-scale effects of dust storms in the lower atmosphere of Mars are numerous. This presentation addresses the less studied aspect of dust storms—their manifestation and consequences in the upper atmosphere. The most comprehensive observational data set to date of upper atmospheric densities during dust storms was presented by Withers and Pratt...

We address the effect of an additional infrared radiative cooling/heating of the mesosphere and lower thermosphere (MLT) in the infrared bands of CO2, O3 and H2O due to small-scale irregular temperature fluctuations associated with gravity waves (GWs). These disturbances are not well resolved by present general circulation models (GCMs), but they a...

Vertical coupling by gravity waves (GWs) between the lower atmosphere and thermosphere is studied with a general circulation model (GCM) extending from the tropopause to the upper atmosphere. A newly developed nonlinear spectral GW parameterization, which accounts for wave propagation in the highly dissipa-tive thermosphere, has been implemented in...

We examine for the first time the propagation of gravity waves (GWs) of lower atmospheric origin to the thermosphere above the turbopause during a sudden stratospheric warming (SSW). The study is performed with the Coupled Middle Atmosphere-Thermosphere general circulation model and the implemented spectral GW parameterization of Yiǧit et al. (2008...