Figure 8 - uploaded by Philippe Keckhut
Content may be subject to copyright.
Synoptic map of geopotential (m 2 /s 2 ) at 70 km on 25 December 1991, scaled by 1000, derived from UARS observations. Superposed are regions of negative lapse rate (shaded).
Source publication
1] Mesospheric inversions are studied in vertical soundings from the French lidar at Observatoire de Haute-Provence and in synoptic global structure that was observed simultaneously by the UARS satellite. The latter provides the instantaneous three-dimensional (3-D) structure of the circulation that accompanies mesospheric inversions. A numerical s...
Contexts in source publication
Context 1
... The relationship to horizontal wave structure, seen earlier in temperature, is even clearer in geopotential. Figure 8 shows, for December 25, 1991, the synoptic map of È at 70 km. The wave field is amplified at middle and high latitudes. ...
Context 2
... structure resembles the much noisier pattern of indi- vidual UARS soundings collected on this day [Leblanc et al., 1995]. The synoptic structure in Figure 8, on the other hand, describes changes that operate coherently (and are therefore resolved in the asynoptic measurements). It reveals a continuous anomaly of negative lapse rate that extends from 90°W to 90°E. ...
Similar publications
We study the seasonal evolution of Titan's lower stratosphere (around 15~mbar) in order to better understand the atmospheric dynamics and chemistry in this part of the atmosphere. We analysed Cassini/CIRS far-IR observations from 2006 to 2016 in order to measure the seasonal variations of three photochemical by-products: $\mathrm{C_4H_2}$, $\mathrm...
![Figure 4. Response of the OGWD [m/s/day] at the 50 hPa (top), 30 hPa...](publication/322452217/figure/fig2/AS:582157283151872@1515808520940/Response-of-the-OGWD-m-s-day-at-the-50-hPa-top-30-hPa-middle-and-10-hPa-bottom_Q320.jpg)
Gravity wave drag (GWD) is an important driver of the middle atmospheric dynamics. However, there are almost no observational constraints on its strength and distribution (especially horizontal). In this study we analyze orographic GWD (OGWD) output from Canadian Middle Atmosphere Model simulation with specified dynamics (CMAM-sd) to illustrate an...
The medium frequency radar deployed at Tirunelveli (8.7°N, 77.8°E), which is located near the southmost tip of peninsular India, have been providing continuous data from the year 1993 to the year 2012 that helped to study the long term tendencies in the lunar tidal variabilities over this geographic location. In the present paper we present the res...
This paper synthesizes and reviews progress in recent researches on the atmospheric dynamics in the stratosphere and its dynamical interaction with the tropospheric processes, with focuses on the dynamics of quasi-stationary planetary waves, the wave-basic flow interaction in the tropical stratosphere, the impact of atmospheric circulation variabil...
Pockets of low ozone have been observed on numerous occasions in anticyclones at middle to high latitudes in the middle stratosphere. Air masses within the anticyclones at altitudes near 850 K (∼32 km) contain ∼25% less ozone than the surrounding air. Trajectory calculations have revealed that much of the air within the pockets originates in the tr...
Citations
... role of gravity wave dissipation in the MIL's persistence, and showed that this process strongly depends on the temperature and the background wind. Salby et al. (2002) and Sassi et al. (2002) cfocused on the mechanism of MIL creation and revealed with simulations that the planetary wave breaking is supposed to occur in the same altitude range of a weak zonal wind region. The wind behavior during MIL events is an essential component of understanding the MIL phenomenon and, more broadly, the impacts on general middle atmosphere circulation. ...
The mesospheric inversion layer (MIL) phenomenon is a temperature enhancement (10–50 K) in a vertical layer (∼10 km) lasting several days and spanning thousands of kilometers within the mesosphere. As MILs govern the mesospheric variability, their study is crucial for a better understanding of the middle‐atmosphere global circulation. MIL phenomenon is also important for applications in aeronautics as perturbations in the mesosphere are significant issues for the safe reentry of rockets, space shuttles, or missiles. However, the description of this phenomenon remains incomplete, since no observations of MIL's effects on winds exist, hampering an understanding of the mechanisms responsible for their formation. This study investigates simultaneous wind‐temperature observations in the altitude range of 30–90 km during MIL events. Strong winds deceleration occurred in the same altitude range as the temperature inversion, confirming the role of gravity waves in MIL's formation mechanisms.
... It is generally considered that the lower MILs have two formation mechanisms: Firstly, when large, upward-propagating planetary waves reach an altitude where their phase speed matches the speed of the background horizontal wind, the waves break down, dissipate via turbulence, and begin to deposit momentum and energy into the atmosphere. This process acts to slow and potentially reversing the background wind and provide local heating, which reverses the local temperature lapse rate and creates the inversion layer [7]. Secondly, gravity waves can also saturate and interact with the mean horizontal wind in the same fashion as planetary waves. ...
... • PW breaking, GW breaking and turbulent mixing, and/or GW-tidal interactions that focus GW breaking [7,[44][45][46]; • Tropopause and polar-summer mesopause climatological inversions [47,48]; • Reactions to large-amplitude GWs that induce strong wind shears and huge fluctuations in local static stability, as evidenced in stratospheric temperature and wind profiles and MLT [49,50]; • Multiscale dynamics that produce "sheet and layer" structures are easily observable from the surface into the MLT due to wave-wave and wave-mean-flow interactions, instabilities, and turbulence accompanying superposed GWs [51][52][53]. ...
... Whatever the initial cause of MIL generation, either tides, gravity waves, or planetary waves, the dissipation of the gravity waves could maintain a quite stable temperature inversion as the breaking of waves occurs preferably inside and above the inversion layer [2]. Salby et al. [7] seems to indicate that planetary waves could induce MIL. This effect can occur preferably in the lower mesosphere, where the largest anomalies associated with stratospheric warming are observed. ...
A climatology of Mesospheric Inversion Layers (MIL) has been created using the Rayleigh lidar located in the south of France at L’Observatoire de Haute Provence (OHP). Using criteria based on lidar measurement uncertainties and climatological mean gravity wave amplitudes, we have selected significant large temperature anomalies that can be associated with MILs. We have tested a novel approach for classifying MILs based on a k-mean clustering technique. We supplied different parameters such as the MIL amplitudes, altitudes, vertical extension, and lapse rate and allowed the computer to classify each individual MIL into one of three clusters or classes. For this first proof of concept study, we selected k = 3 and arrived at three distinct MIL clusters, each of which can be associated with different processes generating MILs in different regimes. All clusters of MIL exhibit a strong seasonal cycle with the largest occurrence in winter. The four decades of measurements do not reveal any long-term changes that can be associated with climate changes and only show an inter-annual variability with a quasi-decadal oscillation.
... The review article by Meriwether and Gardner [26] notes that these "double MILs" are common. The lower MILs that form between 65 and 80 km are likely the result of planetary waves and GWs breaking through interactions with the winds [11,28], while the upper MILs, between 85 and 100 km, are likely driven by GWs interacting with winds and by non-linear effects such as wave-wave interactions [26]. Recently, lidar and SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) measurements onboard the TIMED (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics) satellite [29] have suggested the presence of a third MIL located above 95 km, which is primarily driven by chemical heating by atomic oxygen [30]. ...
... Planetary waves, Kelvin waves, and tides larger than our nightly lidar datasets (four to nine hours) could also have a significant influence [28,39]. Unfortunately, we cannot replicate the 10-day continuous lidar study conducted by Baumgarten et al. [40], which was able to assess the contribution of longer-period waves. ...
During a recent 2020 campaign, the Rayleigh lidar aboard the Bâtiment d’Essais et de Mesures (BEM) Monge conducted high-resolution temperature measurements of the upper Mesosphere and Lower Thermosphere (MLT). These measurements were used to conduct the first validation of ICON-MIGHTI temperatures by Rayleigh lidar. A double Mesospheric Inversion Layer (MIL) as well as shorter-period gravity waves was observed. Zonal and meridional wind speeds were obtained from locally launched radiosondes and the newly launched ICON satellite as well as from the European Centre for Medium-Range Weather Forecasts (ECMWF-ERA5) reanalysis. These three datasets allowed us to see the evolution of the winds in response to the forcing from the MIL and gravity waves. The wavelet analysis of a case study suggests that the wave energy was dissipated in small, intense, transient instabilities about a given wavenumber in addition to via a broad spectrum of breaking waves. This article will also detail the recent hardware advances of the Monge lidar that have allowed for the measurement of MILs and gravity waves at a resolution of 5 min with an effective vertical resolution of 926 m.
... Further study shows the average height of the bottoms of the MIL whose thickness is 3 reach to 69.2 km, and the inverse temperature range is 18.3 K, which indicates a contrary result to the previous reports (Fechine J. et al., 2008) [1]; i.e., the average height of the bottom boundary of lower MIL is higher than those of similar phenomena, and the temperature amplitude is lower as well. Salby et al. [28] reported that the large-scale circulation distortion under the influence of planetary waves will cause temperature inversion temporally and spatially, and those of the smaller-scale MIT may be caused by gravity waves. Later, Ramesh et al. indicated that the main mechanism of the MIL can be ascribed to the gravity wave breaking, and the amplitude of MIT are affected by the gravity wave and planetary waves interactions [18]. ...
Based on 139 nights of observational data of the Rayleigh lidar site in Beijing, China (40.5° N, 116.2° E), typical lower MIL cases and their temperature inversion evolution process were reported and compared with the SABER data from the same time. Meanwhile, the seasonal distribution of lower MIL cases over North China was also statistically analyzed. The average inversion temperature of the low MIL is 23.4 K, and the average layer thickness is 4.78 km with an average MIL bottom altitude of 68.2 km. Meanwhile, 65% of the MIL propagates vertically, most of which goes downward. These results show the temperature behavior properties of the lower MIL over North China, which may be helpful for us to further understand middle atmosphere chemical and dynamics processes.
... MILs are layers of increasing temperature in the mesosphere that represent a departure from the expected negative temperature gradient (see review by Meriwether & Gerrard, 2004). Breaking planetary waves, tides, and gravity waves have all been shown to generate MILs (Liu et al., 2000;Liu & Meriwether, 2004;Salby et al., 2002;Sassi et al., 2002). The presence of a persistent adiabatic negative temperature gradient on the topside of the MILs is consistent with a wellmixed turbulent layer (Whiteway et al., 1995). ...
... The data reveal a relatively weak planetary wave-1 that was propagating westward with altitude. The regions where the phase of the wave changed abruptly in altitude with coincident temperature inversions indicate planetary wave breaking (e.g., 55 km, 210°-270°E; France et al., 2015;Irving et al., 2014;Salby et al., 2002). These phase changes are also evident in the lower panel, where we plot the geopotential height perturbation as a function of altitude and latitude. ...
Measurements of turbulence and waves were made as part of the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25–26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket-borne ionization gauge measurements revealed turbulence in the 70- to 88-km altitude region with energy dissipation rates between 0.1 and 24 mW/kg with an average value of 2.6 mW/kg. The eddy diffusion coefficient varied between 0.3 and 134 m²/s with an average value of 10 m²/s. Turbulence was detected around mesospheric inversion layers (MILs) in both the topside and bottomside of the MILs. These low levels of turbulence were measured after a minor sudden stratospheric warming when the circulation continued to be disturbed by planetary waves and winds remained weak in the stratosphere and mesosphere. Ground-based lidar measurements characterized the ensemble of inertia-gravity waves and monochromatic gravity waves. The ensemble of inertia-gravity waves had a specific potential energy of 0.8 J/kg over the 40- to 50-km altitude region, one of the lowest values recorded at Chatanika. The turbulence measurements coincided with the overturning of a 2.5-hr monochromatic gravity wave in a depth of 3 km at 85 km. The energy dissipation rates were estimated to be 3 mW/kg for the ensemble of waves and 18 mW/kg for the monochromatic wave. The MTeX observations reveal low levels of turbulence associated with low levels of gravity wave activity. In the light of other Arctic observations and model studies, these observations suggest that there may be reduced turbulence during disturbed winters.
... Satellite observations showed the global extend of MILs (Leblanc et al., 1997;Fechine et al., 2008;Gan et al., 2012). Several explanations have been proposed to explain the formation of MILs including gravity wave breaking (Hauchecorne and Maillard, 1990), planetary wave structure (Salby et al., 2002) and thermal tides (Meriwether et al., 1998). Explanations of the long duration and the global longitudinal 15 extend of the observed equatorial MILs are beyond the scope of this paper and will be the topic of a future publication. ...
Given that the scattering of sunlight by the Earth's atmosphere above 30–35km is primarily due to molecular Rayleigh scattering, the intensity of scattered photons can be assumed to be directly proportional to the atmospheric density. From the measured relative density profile it is possible to retrieve an absolute temperature profile by assuming local hydrostatic equilibrium, the perfect gas law, and an a priori temperature from a climatological model at the top of the atmosphere. This technique is applied to Rayleigh lidar observations for over 35 years. The GOMOS star occultation spectrometer included spectral channels to observe daytime limb scattered sunlight close to the star direction. GOMOS Rayleigh scattering profiles in the spectral range 420–480nm have been used to retrieve temperature profiles in the altitude range 35–85km with a 2-km vertical resolution. A database of more than 309,000 temperature profiles has been created.
A global climatology was built and compared to GOMOS external model. In the upper stratosphere, where the external model is based on ECMWF analysis, the agreement is better than 2K. In the mesosphere, where the external model follows MSIS climatology, 5 to 10K differences are observed. Comparison with nighttime collocated Rayleigh lidar profiles above south of France shows some differences with a vertical structure that may be at least partially explained by the contribution of thermal diurnal tide.
The temperature evolution obtained at Equator indicates the occurrence of mesospheric inversion layers in the temperature profile with global longitudinal extension, descending in about one month from 80 to 70km. The climatology shows a semi-annual variation in the upper stratosphere, a stratopause altitude varying between 47 and 54km and an annual variation in the mesosphere.
The technique to derive temperature profiles from Rayleigh scattering at limb can be applied to any other limb-scatter sounder providing observation in the spectral range 350–500nm. This is also a good candidate for a future small satellite constellation due to the simplicity of the principle.
... Large inversions develop during episodes of planetary wave amplification. Ref. [4] showed that the vertical structure of planetary waves alters from westward tilt and upward amplification below the mesospheric inversion layer to nearly barotropic structure and upward decay above the inversion. ...
We analyse middle atmospheric profiles of temperature, geopotential height, water vapour volume mixing ratio, and ozone volume mixing ratio above Bern (46.95 ∘ N, 7.44 ∘ E). These profiles were observed by the satellite experiment Aura/MLS and the ground-based microwave radiometers MIAWARA and GROMOS at Bern. The data series of Aura/MLS and GROMOS extend from the winter 2004/2005 to the winter 2017/2018 while the MIAWARA series starts in winter 2007/2008. Mesospheric inversion layers (MILs) above Bern, Switzerland are often present during the winter season, and the temperature peak of the MIL is located at an altitude of about 81 km in winter. The occurrence rate of the MIL during the winter season above Bern is about 42%. The MILs are possibly associated with planetary wave breaking processes in the mesospheric surf zone at mid-latitudes during winter. The study only evaluates daily averages in order to reduce tidal influences. Composite atmospheric profiles are computed for times when the MIL is present and for times when the MIL is absent. The difference of the composites indicates that middle and upper stratospheric ozone are reduced by up to 7% when the MIL is present while lower mesospheric water vapour is enhanced by up to 20% during the MIL occurrence. Using wind data of ECMWF operational analysis, we find that eastward and northward winds are decelerated by about 5–15 m/s in the lower mesosphere during the occurrence of an MIL. We also find that the occurrence of an MIL above Bern is not a regional process, but it depends on the movements and deformations of the polar mesospheric vortex. During an MIL, the location of Bern is outside of the lower mesospheric vortex. These new findings of atmospheric composition and circulation changes support the assumption that winter MILs at mid-latitudes are connected to planetary wave breaking in the middle atmosphere.
... Many authors have argued for various source dynamics and/or modeled potential formation mechanisms. It is now well established, for example, that large-scale MILs accompany planetary wave (PW) dynamics in the "surf zone" near a zero wind line, based on extensive satellite measurements and known PW dynamics (e.g., Salby et al., 2002;Oberheide et al., 2006). It is also known that large-amplitude tides or GWs often lead to features resembling MILs and that these are likely to influence GW propagation, instability, and turbulence generation (e.g., F17a). ...
A companion paper by Fritts, Laughman, et al. (2017) employed an anelastic numerical model to explore the dynamics of gravity waves (GWs) encountering a mesospheric inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. That study revealed that MIL responses, including GW transmission, reflection, and instabilities, are sensitive functions of GW parameters. This paper expands on two of the Fritts, Laughman, et al. (2017) simulations to examine GW instability dynamics and turbulence in the MIL; forcing of the mean wind and stability environments by GW, instability, and turbulence fluxes; and associated heat and momentum transports. These direct numerical simulations resolve turbulence inertial‐range scales and yield the following results: GW breaking and turbulence in the MIL occur below where they would otherwise, due to enhancements of GW amplitudes and shears in the MIL.
2‐D GW and instability heat and momentum fluxes are ~20–30 times larger than 3‐D instability and turbulence fluxes.
Mean fields are driven largely by 2‐D GW and instability dynamics rather than 3‐D instabilities and turbulence.
2‐D and 3‐D heat fluxes in regions of strong turbulence yield small departures from initial T(z) and N²(z) profiles, hence do not yield nearly adiabatic “mixed” layers.
Our MIL results are consistent with the relation between the turbulent vertical velocity variance and energy dissipation rate proposed by Weinstock (1981) for the limited intervals evaluated.
... These layers can be~2-10 km in depth below a local temperature maximum exceeding the background profile mean by~20-50 K or more. Observations and modeling at global and regional scales reveal that MILs accompany PW breaking below a zero wind line in the PW surf zone, where the PW exhibits an abrupt phase change in the vertical (e.g., France et al., 2015;Gan, Zhang, & Yi, 2012;Irving et al., 2014;Meriwether & Gerrard, 2004;Oberheide et al., 2006;Salby et al., 2002;Sassi et al., 2002;Wu, 2000). These large-scale MILs typically have horizontal scales of several thousand kilometers or more and little or no vertical motion. ...
... As noted above, satellite, ground-based, and in situ observations have been interpreted as evidence of MILs at altitudes from the stratosphere into the lower thermosphere for many years. Large-scale MILs extending large distances in satellite observations or descending slowly with the phase of tidal motions have been attributed to PW structure near a zero-wind line (or critical level) or large-amplitude tides that may or may not involve GW-tidal interactions (e.g., Meriwether & Gerrard, 2004;Oberheide et al., 2006;Salby et al., 2002;Williams et al., 2006). Other observations by lidars and/or in situ probes in the stratosphere and mesosphere have identified regions of positive dT/dz as MILs, often with nearly adiabatic layers above, that may or may not include tidal contributions. ...
An anelastic numerical model is employed to explore the dynamics of gravity waves (GWs) encountering a mesosphere inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. Instabilities occur within the MIL when the GW amplitude approaches that required for GW breaking due to compression of the vertical wavelength accompanying the increasing static stability. Thus MILs can cause large-amplitude GWs to yield instabilities and turbulence below the altitude where they would otherwise arise. Smaller amplitude GWs encountering a MIL do not lead to instability and turbulence, but do exhibit partial reflection and transmission, and the transmission is a smaller fraction of the incident GW when instabilities and turbulence arise within the MIL. Additionally, greater GW transmission occurs for weaker MILs and for GWs having larger vertical wavelengths relative to the MIL depth and for lower GW intrinsic frequencies. These results imply similar dynamics for inversions due to other sources, including the tropopause inversion layer, the high stability capping the polar summer mesopause, and lower-frequency GWs or tides having sufficient amplitudes to yield significant variations in stability at large and small vertical scales. MILs also imply much stronger reflections and less coherent GW propagation in environments having significant fine structure in the stability and velocity fields than in environments that are smoothly varying.
... The mesospheric temperature inversions can normally classified into lower and upper MILs. The lower MILs (~65-80 km) are believed to be due to planetary wave (PW) breaking [Salby et al., 2002;Ramesh et al., 2013a], and the upper MILs (above~80-90 km) are dominantly due to gravity wave tidal interaction and/or chemical heating [Meriwether and Gerrard, 2004;Sridharan et al., 2008;Ramesh et al., 2013bRamesh et al., , 2014. Sassi et al. [2002] verified the interaction of PW, and mesospheric surf zone can produce MILs at 80-85 km during winter. ...
The various occurrence characteristics of day and night tropical (10°N-15°N, 60°E-90°E) mesospheric inversion layers (MILs) are studied using TIMED-SABER (Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics-Sounding of the Atmosphere using Broadband Emission Radiometry) satellite data products of kinetic temperature, volume mixing ratios of O, H, and O 3 , volume emission rates of O 2 (1 Δ) and OH (1.6μm channel), chemical heating rates due to seven dominant exothermic reactions among H, O, O 2 , O 3 , OH, HO 2 , and CO 2 cooling rates for the year 2011. Although both dynamics and chemistry play important roles, the present study mainly focuses on the chemical processes involved in the formation of day and night MILs. It is found that the upper level height of daytime (nighttime) MIL descends (ascends) from ~88 km (~80 km) in winter to ~72 km (~90 km) in summer. The day and night inversion amplitudes are correlated with total chemical heating rates and CO 2 cooling rates and they show semi annual variation with larger (smaller) values during equinoxes (solstices). The daytime (nighttime) inversion layers are predominantly due to the exothermic reaction, R 5 : O+O+M→O2 +M and R 6 : O+O2 +M→O3 +M (R 3 : H+O3 →OH+O2). In addition, the CO2 causes large cooling at the top and small heating at the bottom levels of both day and night MILs. In the absence of dynamical effects, the chemical heating and CO2 cooling jointly contribute for the occurrence of day and night MILs.
