Internal wave coupling processes in Earth's atmosphere

A review of vertical coupling in the Atmosphere–Ionosphere system: Effects of waves, sudden stratospheric warmings, space weather, and of solar activity

A strong mountain wave, observed over Central Europe on 12 January 2016, is simulated in 2D under two fixed background wind conditions representing opposite tidal phases. The aim of the simulation is to investigate the breaking of the mountain wave and subsequent generation of nonprimary waves in the upper atmosphere. The model results show that the mountain wave first breaks as it
approaches a mesospheric critical level creating turbulence on horizontal scales of 8–30 km. These turbulence scales couple directly to horizontal secondary waves scales, but those scales are prevented from reaching the hermosphere by the tidal winds, which act like a filter.
Initial secondary waves that can reach
the thermosphere range from 60 to 120 km in horizontal scale and are influenced by the scales of the
horizontal and vertical forcing associated with wave breaking at mountain wave zonal phase width, and
horizontal wavelength scales. Large-scale nonprimary waves dominate over the whole duration of the
simulation with horizontal scales of 107–300 km and periods of 11–22 minutes. The thermosphere winds
heavily influence the time-averaged spatial distribution of wave forcing in the thermosphere, which peaks
at 150 km altitude and occurs both westward and eastward of the source in the 2 UT background
simulation and primarily eastward of the source in the 7 UT background simulation. The forcing
amplitude is ∼2× that of the primary mountain wave breaking and dissipation. This suggests that
nonprimary waves play a significant role in gravity waves dynamics and improved understanding of the
thermospheric winds is crucial to understanding their forcing distribution.

/pdf/secondary-gravity-waves-generated-by-breaking-mountain-waves-4jt21r6wxe.pdf

Secondary Gravity Waves Generated by Breaking Mountain Waves Over Europe

The 11 March 2011 Tohoku earthquake generated a massive tsunami off the Pacific coast of Japan, which launched intense atmospheric gravity waves (AGWs) in the atmosphere. Within the context of this study, the Tohoku tsunami event was unique in the sense that it enabled a rare, controlled experiment for investigating how AGWs are launched, propagate, and dissipate in relation to tsunamis. This tsunami was a long-lived, rapidly traveling source of a rich spectra of AGWs excited just above the ocean-atmosphere interface. In this paper we use GPS total electron content (TEC) data from the United States (U.S.) to look for these AGWs in the ionosphere via their signatures as traveling ionospheric disturbances (TIDs). We find a spectrum of TIDs in the TEC data propagating in the direction of the tsunami that last for several hours over the West Coast of the U.S. and as far inland as western Colorado. The observed TIDs have periods that range from 14 to 30min, horizontal wavelengths that range from 150 and 400 km, and horizontal phase speeds that range from 180 to 260m/s. We use reverse ray tracing to show that the Tohoku tsunami was likely the source of these TIDs. Using the networks of GPS receivers in the U.S., we map the tsunami-launched TIDs over the western U.S. and investigate the spectrum of gravity waves enabling an enhanced understanding/verification of the properties of AGWs as a function of the launch angle.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016JA023659

Traveling ionospheric disturbances over the United States induced by gravity waves from the 2011 Tohoku tsunami and comparison with gravity wave dissipative theory

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 general circulation models. Since the spatial scales of gravity waves are smaller than the typical spatial resolution of most models, atmospheric forcing produced by them must be parameterized. This paper presents a review of gravity waves in planetary atmospheres, outlines their main characteristics and forcing mechanisms, and summarizes approaches to capturing gravity wave effects in numerical models. The main goal of this review is to bridge research communities studying atmospheres of Earth and other planets.

https://www.mdpi.com/2073-4433/10/9/531/pdf

Gravity Waves in Planetary Atmospheres: Their Effects and Parameterization in Global Circulation Models

We use a nonlinear, fully compressible, two-dimensional numerical model to study the effects of dissipation on gravity wave packet spectra in the thermosphere. Numerical simulations are performed to excite gravity wave packets using either a time-dependent vertical body forcing at the bottom boundary or a specified initial wave perturbation. Three simulation case studies are performed to excite (1) a steady state monochromatic wave, (2) a spectrally broad wave packet, and (3) a quasi-monochromatic wave packet. In addition, we analyze (4) an initial condition simulation with an isothermal background. We find that, in cases where the wave is not continually forced, the dominant vertical wavelength decreases in time, predominantly due to a combination of refraction from the thermosphere and dissipation of the packets' high frequency components as they quickly reach high altitude. In the continually forced steady state case, the dominant vertical wavelength remains constant once initial transients have passed. The vertical wavelength in all simulations increases with altitude above the dissipation altitude (the point at which dissipation effects are greater than the wave amplitude growth caused by decreasing background density) at any fixed time. However, a shift to smaller vertical wavelength values in time is clearly exhibited as high-frequency, long vertical wavelength components reach high altitudes and dissipate first, to be replaced by slower waves of shorter vertical wavelength. Results suggest that the dispersion of a packet significantly determines its spectral evolution in the dissipative thermosphere.

/pdf/thermospheric-dissipation-of-upward-propagating-gravity-wave-3yular5oiu.pdf

Thermospheric Dissipation of Upward Propagating Gravity Wave Packets

Intention of this study is to explore the impact of non-similar modeling on mixed convective Williamson magnetized nanofluid flow over a vertically placed stretching surface with the consideration of engine oil as base fluid and molybdenum disulfide (MoS2) as nanoparticles. The features of viscous dissipation, Darcy resistance and heat source factor are also incorporated to examine the thermal prospective. The considered flow phenomenon is designated in the form of governing partial differential equations (PDEs) by employing the concepts of Boussinesq approximations and boundary layer approach. By introducing non-similar transformations, the governing system is redesigned into dimensionless non-similar nonlinear PDEs. The dimensionless non-similar framework is examined analytically by implementing local non-similarity and then stimulated numerically via bvp4c to explore the impacts of vital numbers on velocity and temperature distribution. The velocity distribution, temperature field, skin friction coefficient and local Nusselt number are elaborated through graphs and tables by altering the inputs of emerging parameters. The computations illustrate that the escalating inputs of magnetic field and porosity parameter appear as the hindering factors against flow velocity. It is also discovered that with the increasing estimations of nanoparticles volume fraction leads an enhancement in the temperature distribution and decline in velocity profile. Furthermore, in a restricted case the validity of results is found to be in good agreement with the published literature. A suitable range of stable solutions is obtained for emerging parameters. 

Non-similar mixed convection analysis for magnetic flow of Williamson nano-fluid over vertically stretching surface subjected to viscous dissipation, porous media and heat sou

The focus of this manuscript is to investigate numerically the free convection of a single-wall carbon nanotube-water non-Newtonian nanofluid saturating an inclined square porous medium, where the Dupuit-Darcy model is used for modeling the fluid flow inside the cavity along with the Carreau-Yasuda model for describing the apparent viscosity of the nanofluid. The top and bottom walls of the enclosure are kept adiabatic, whereas the others are differentially heated. The governing parameters for the problem are the Rayleigh number, nanotubes volume fraction, inertial effect parameter, the Carreau-Yasuda non-Newtonian parameters as well as the inclination angle of the cavity. The finite difference method is used to resolve the governing partial differential equations of the problem. The obtained results are presented through graphs, streamlines, isotherms, and apparent viscosity contours. In addition, a scale analysis is presented to show the maximum heat transfer enhancement recorded. As a matter of fact, the obtained momentum equation enables the analysis of the Newtonian and non-Newtonian behavior of the nanofluid along with the Darcy and the departure from Darcy situation. The findings show that the increase of the single-wall carbone nanotube (SWCNT) percentage significantly enhances the heat transfer even with the increase of the fluid viscosity. Furthermore, the increase of inertial effect parameter inhibits the flow inside the cavity and causes a decrease in the convection rate. In actual fact the power-law index parameter of the Carreau-Yasuda model has a significant effect on the fluid flow strength as well as the convection rate inside the enclosure, i.e., the more the shear thinning the fluid, the better is the rate of convection. The inclination angle of -30&amp;deg; presents better angle for maximum convection rate. An enhancement of 8&amp;#37; in convection rate is recorded for the case of the Newtonian behavior, while for the shear-thinning situation the enhancement reaches eight times of that recorded of Newtonian condition. 

Enhancement of Dupuit-Darcy Free Convection Heat Transfer of SWCNT-Water non-Newtonian Nanofluid Saturated Porous Medium with Inertial Effect Consideration

C. J. Ali

Papers

Thermospheric Dissipation of Upward Propagating Gravity Wave Packets

Non-similar mixed convection analysis for magnetic flow of Williamson nano-fluid over vertically stretching surface subjected to viscous dissipation, porous media and heat sou

Enhancement of Dupuit-Darcy Free Convection Heat Transfer of SWCNT-Water non-Newtonian Nanofluid Saturated Porous Medium with Inertial Effect Consideration