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To investigate the stratosphere-troposphere exchange (STE) process induced by the gravity waves (GWs) caused by Typhoon Molave (2020) in the upper troposphere and lower stratosphere, we analyzed the ERA5 reanalysis data provided by the European Centre for Medium-Range Weather Forecasts and the CMA Tropical Cyclone Best Track Dataset. We also adopted the mesoscale forecast model Weather Research and Forecasting model V4.3 for numerical simulation. Most of the previous studies were about typhoon-induced STE and typhoon-induced GWs, while our research focused on the STE caused by typhoon-induced gravity waves. Our analysis shows that most of the time, the gravity wave signal of Typhoon Molave appeared below the tropopause. It was stronger on the east side of the typhoon center (10°-20°N, 110°-120°E) than on the west side, suggesting an eastward tilted structure with height increase. When the GWs in the upper troposphere and lower stratosphere region on the west side of the typhoon center broke up, it produced strong turbulence, resulting in stratosphere-troposphere exchange. At this time, the average potential vorticity vertical flux increased with the average ozone mass mixing ratio. The gravity wave events and STE process simulated by the WRF model were basically consistent with the results of ERA5 reanalysis data, but the time of gravity wave breaking was different. This study indicates that after the breaking of the GWs induced by typhoons, turbulent mixing will also be generated, and thus the STE. [ABSTRACT FROM AUTHOR]

Atmospheric gravity waves (GWs) can strongly modulate middle atmospheric circulation and can be a significant factor for the coupling between the lower atmosphere and the middle atmosphere. GWs are difficult to resolve in global atmospheric models due to their small scale; thus, GW observations play an important role in middle atmospheric studies. The climatology of GW variance and momentum in the low-latitude mesosphere and lower thermosphere (MLT) region are revealed using multiple meteor radars, which are located at Kunming (25.6°N, 103.8°E), Sanya (18.4°N, 109.6°E), and Fuke (19.5°N, 109.1°E). The climatology and longitudinal variations in GW momentum fluxes and variance over the low-latitude region are reported. The GWs show strong seasonal variations and can greatly control the mesospheric horizontal winds via modulation of the quasi-geostrophic balance and momentum deposition. The different GW activities between Kunming and Sanya/Fuke are possibly consistent with the unique prevailing surface winds over Kunming and the convective system over the Tibetan Plateau according to the European Centre for Medium-Range Weather Forecasts (ECMWF), Reanalysis v5 (ERA5) data, and outgoing longwave radiation (OLR) data. These findings provide insight for better understanding the coupling between the troposphere and mesosphere. [ABSTRACT FROM AUTHOR]

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Adjoint sensitivity modeling plays an important role in inverse problems, including four‐dimensional variational data assimilation or state estimation, by providing the sensitivity of the objective (or cost) function to the model input data. Although data assimilation has become common in regional ocean modeling, and the model resolution has become high enough to resolve internal tides, it remains unclear whether physically sensible and stable adjoint sensitivity modeling is feasible in the presence of internal waves. As a first step to tackle this problem, this study investigates fundamental properties of the adjoint of a time‐dependent circulation model, and the resulting sensitivity under internal waves. The theoretical and numerical results, based on simple‐internal‐wave theory and MITgcm modeling, show that stable adjoint sensitivity modeling is feasible under fully nonlinear (but stable) hydrostatic internal waves. However, it requires a careful choice of the objective function to obtain sensitivity which has the same propagation properties as (real‐world) internal waves, because the definition primarily controls the directionality and vertical‐mode content of internal‐wave signals in the adjoint model. Also, it should be noted that the internal‐wave signals lack indirect sensitivity through the dependence of the wave‐propagation speed on the model's prognostic variables. An important implication of the results is that the standard form of the objective function, which has been used in data assimilation studies for quasi‐geostrophic flows and barotropic tides, could be problematic for internal tides. Plain Language Summary: A particular method, called adjoint sensitivity calculation, is often used to incorporate observations into numerical simulations, such as weather forecasts. There is a growing need for this sensitivity calculation in regional ocean modeling in the presence of internal waves. Unlike the familiar ocean surface waves, internal waves exist within the ocean interior and have wavelengths of tens of km. This study uses theoretical analysis and numerical modeling to demonstrate that adjoint sensitivity calculation is feasible in the presence of internal waves, and to illustrate fundamental properties of the sensitivity. The results imply that standard assumptions currently used to incorporate observations into numerical simulations may not always work in the presence of internal waves, and suggests how the assumptions could be modified. Key Points: It is feasible to use an adjoint model to obtain sensitivity which has the same propagation properties as fully nonlinear internal wavesInternal‐wave signals in an adjoint model have different natural structure, or modes, from internal waves under real‐world physicsThe objective function definition primarily controls directionality and vertical‐mode content of internal‐wave signals in an adjoint model [ABSTRACT FROM AUTHOR]

The characteristics of gravity waves in China are investigated through an extensive analysis of high vertical resolution radiosonde observations collected over eight years across 120 stations, and are subsequently compared to those in the United States. These characteristics encompass energy density, intrinsic frequencies, horizontal and vertical wavelengths, as well as vertical and horizonal propagation directions. China and the United States, situated in mid‐latitude regions with prominent western topographical features, the Qinghai‐Tibet Plateau and Rocky Mountains respectively, demonstrate striking similarities in the generation and distribution of gravity waves. Both landmasses exhibit the strongest gravity waves during winter and the weakest during summer. And within the troposphere, the maximum energy of gravity waves is generated over and immediately downstream of the topographies. In addition, the energy level is amplified in the lower stratosphere. However, unique regional contrasts in summer are result from the differences of summer monsoon influence and the distinct western topographies. The maximum gravity wave energy in summer troposphere is observed over the north side of the Qinghai‐Tibet Plateau in China, contrasting with its location downstream of the Rockies in the United States. Plain Language Summary: Extensive studies have highlighted the global circulation effects of small‐scale atmospheric gravity waves, but our knowledge of the global distribution of gravity waves remains incomplete. High vertical resolution raw radiosonde data achieved at meteorological sounding stations present a potentially invaluable resource of deriving information on gravity waves. Previous studies have used these data achieved in China at a small subset of stations to analyze limited gravity waves parameters, which cannot provide a fully representative sample of the diverse underlying surface and weather conditions across the country and acquire complete parameters of gravity wave. Our study using the complete data set aims to contribute valuable information on the comprehensive characteristics of gravity wave activities in China, and compare these results to those derived from a similar data set in the United States. The results demonstrate many striking similarities in terms of the generation and distribution of gravity waves in two landmasses. However, unique regional contrasts in summer are result from the differences of summer monsoon influence and the distinct height and shape of their respective western topographies. These results will supplement knowledge of the global distribution of gravity waves and be beneficial to the development of the numerical weather prediction models. Key Points: This study derives characteristics of gravity wave in China using high vertical resolution radiosondeThere are many striking similarities in terms of the generation and distribution of gravity waves in China and the United StatesUnique regional contrasts in summer are result from the differences of summer monsoon influence and the distinct western topographies [ABSTRACT FROM AUTHOR]

Gravity wave (GW) momentum flux spectra help to uncover the mechanisms through which GWs influence momentum transfer in the atmosphere and provide crucial insights into accurately characterizing atmospheric wave processes. This study examines the momentum flux spectra of GWs in the troposphere (2–14 km) and stratosphere (18–28 km) over Koror Island (7.2°N, 134.3°W) using radiosonde data from 2013–2018. Utilizing hodograph analysis and spectral methods, the characteristics of momentum flux spectra are discussed. Given that the zonal momentum flux spectra of low-level atmospheric GWs generally follow a Gaussian distribution, Gaussian fitting was applied to the spectral structures. This fitting further explores the seasonal variations of the zonal momentum flux spectra and the average spectral parameters for each month. Additionally, the GW energy is analyzed using SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite data and compared with the results of the momentum flux spectra from radiosonde data, revealing the close negative correlation between wave energy and wave momentum for stratospheric GW changing with time. The findings indicate that the Gaussian peak shifts more eastward in both the troposphere and stratosphere, primarily due to the absorption of eastward-propagating GWs by the winter tropospheric westerly jet and critical layer filtering. The full width at half maximum (FWHM) in the stratosphere is larger than in the troposphere, especially in June and July, as the spectrum broadens due to propagation effects, filtering, and interactions among waves. The central phase speed in the stratosphere exceeds that in the troposphere, reflecting the influences of Doppler effects and background wind absorption. The momentum flux in the stratosphere is lower than in the troposphere, which is attributed to jet absorption, partial reflection, or the dissipation of GWs. [ABSTRACT FROM AUTHOR]

Solar eclipse traveled across South China in the afternoon on 21 June 2020. Five ionosondes located from mid‐to low‐latitudes and on both north and south of the eclipse path were applied to investigate the ionospheric responses. Both the zonal and meridional ranges of the observation region have exceeded 1,000 km. All the five ionosondes had observed the Intermediate Descending Layers (IDLs) simultaneously just after the eclipse maximum and this is a very small probability event. During the solar eclipse, the multi‐hop echoes above the Es, the rising Es to 150 km altitude, the plasma flux from above F2‐layer were also observed and analyzed. The descending trend of the IDLs and the peak height of F2‐layer (hmF2) shows great consistency, indicating the close relationship between the eclipse induced plasma flux and the IDLs. The traces of gravity waves were also found in the IDLs and F‐layer. The plasma flux may carry the ions to valley region and the eclipse produced gravity waves were responsible for the formation of the IDLs. Key Points: Five ionosondes observed the intermediate descending layers simultaneously just after the solar eclipse maximumThe descending trend of the intermediate layers is very similar to that of the F2‐layer peak heightsPlasma flux and gravity waves associated with the solar eclipse are suggested to induce the intermediate descending layers [ABSTRACT FROM AUTHOR]

Upper mesospheric wind data acquired by the medium frequency radar at Kolhapur (16.7°N, 74.2°E) and Modern-Era Retrospective analysis for Research and Application version 2 (MERRA-2) temperature and wind reanalysis datasets are used to investigate the dynamical response of the low-latitude middle atmosphere to the sudden stratospheric warming (SSW) events that occurred during the 2017-18 and 2018-19 winters. When the amplitude of the high-latitude stratospheric planetary wave (PW) of zonal wavenumber one reduces considerably with the onset of the SSW event, the low-latitude mesospheric PW over Kolhapur also shows a considerable reduction in the PW activity. It is noteworthy that the upper mesospheric winds are eastward for approximately 3 weeks after the onset of SSW. The reduced PW activity is associated with the enhanced gravity wave activity in the meridional wind during the SSW 2018-19 event. The plane of propagation of gravity waves obtained from the perturbation ellipse method suggests that their predominant plane of propagation is in the north-south direction. The persistence of the eastward winds is suggested to be due to the interaction of the northward propagating gravity waves with the mean flow, leading to the eastward acceleration due to the Coriolis force. [ABSTRACT FROM AUTHOR]

The object of research is permeable vertical walls (breakwaters) with different degrees of permeability. This paper reports the results of experimental research into the interaction of gravity waves with models of permeable vertical walls (breakwaters), which were formed from cylindrical piles of circular cross-section. With the help of visual and instrumental studies, the features of interaction of surface gravity waves with permeable vertical walls of different permeability have been identified. The degree of wave transformation by these walls was also determined in the form of reflection, transmission, and dissipation coefficients of wave energy. It was established that with a decrease in the permeability of the vertical wall and an increase in the steepness of the initial wave and a decrease in its period, the height of the reflected wave increased. The pattern of the transmitted wave height had the opposite trend. It was determined that the wave reflection coefficient increased with a decrease in the permeability of the vertical wall and the steepness of the initial wave. The wave transmission coefficient had the opposite trend, namely, it increased with increasing wall permeability and with decreasing steepness of the initial wave. The gravity wave energy dissipation coefficient decreased with increasing vertical wall permeability, but for waves with a significant steepness hi/λ>0.038, a decrease in the wave energy dissipation coefficient was observed for walls with low permeability and the appearance of extreme values of this coefficient. Thus, features in the interaction of surface gravity waves with permeable vertical walls (breakwaters) of different permeability have been researched and the degree of wave transformation by these walls has been determined, which could make it possible to effectively design and operate permeable vertical walls as coastal protection structures. [ABSTRACT FROM AUTHOR]

A new version of NCAR Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension (WACCM‐X) has been developed. The main feature of this version is the species‐dependent spectral element (SE) dynamical core solved on a cubed sphere grid, eliminating the polar singularity and enabling simulations at high‐resolutions. Molecular viscosity and diffusion in the horizontal direction are also included. The Conservative Semi‐Lagrangian Multi‐Tracer Transport Scheme (CSLAM) is employed for the species transport. An efficient regridding scheme based on the Earth System Modeling Framework is used to map fields between the physics mesh and geomagnetic grid. Simulations have been performed at coarse (∼200 km and 0.25 scale height) and high (∼25 km and 0.1 scale height) resolutions. Spatial distribution of the resolved gravity waves from the high‐resolution simulations compares well with available observations in the middle and upper atmosphere. Analysis of the scale dependence of the gravity wave energy density and momentum flux shows that, while larger scale waves are dominant energetically at most latitudes, smaller scale waves contribute significantly to the total momentum flux, especially at mid‐high latitudes. The waves in the thermosphere are shown to be strongly modulated by the large‐scale wind through Doppler shift and molecular damping, and they cause large neutral atmosphere and plasma perturbations. Plain Language Summary: Small scale waves can be excited from daily weather near the Earth surface. These waves, termed gravity waves, can propagate upward and are thought to influence the middle and upper atmospheric regions. Such effects, however, are difficult to directly quantify by observations and numerical modeling due to their small scales and global presence. To address this challenge, we have developed a high‐resolution whole atmosphere model (WACCM‐X), which extends from the Earth surface to the upper thermsophere, that can partially resolve the small scale waves. The simulated waves are compared with available observations to verify the model results and to examine how these waves are distributed geographically and over altitudes. The simulations show that wave signatures can be clearly identified in the neutral and the ionized atmosphere, which can have important implications for space weather. Key Points: Gravity wave distribution from lower atmosphere to upper thermosphere obtained from high‐resolution WACCM‐XThermospheric/ionospheric disturbances driven by gravity waves quantifiedWave distribution and disturbance statistics comparable to observations [ABSTRACT FROM AUTHOR]

Mountain gravity wave characteristics are important for analyzing the nighttime heavy rainfall events occurring in Sichuan. Based on the GPM satellite precipitation data, FY-4A satellite cloud data, and ERA5 reanalysis data, we analyze the mesoscale characteristics of a nighttime rainstorm with a gravity wave that occurred on 10-11 July 2018 in the northeastern Sichuan Basin mountains. The results are as follows. (1) The oscillatory feature of cloud water content and the wavelike variation of the potential temperature field reflect, to some extent, the influence of the fluctuations on the mesoscale system. (2) The fluctuation trends of wind vertical shear index, thermal helicity, and moisture helicity appear during the development of waves, indicating the characteristics of gravity waves. (3) The areas with large values of wind vertical shear index, the extreme center of thermal helicity, and moisture helicity are consistent well with the heavy precipitation regions. (4) The gravity wave may be formed by the interaction of topographic disturbances, shear instability, and non-geostrophic equilibrium, which enhance the rainstorm. The regions with a small value of the Richardson number and a nonzero value of the nonlinear equilibrium equation can indicate the location and movement direction of the rainbands. Diagnosis of Richardson number shows that the vertical shear instability is formed before the mesoscale wave is excited, but it decreases with increasing fluctuations, which indicates that part of the energy of the waves comes from the unstable flow.

Due to the significant changes they bring to high latitude stratospheric temperature and wind, stratospheric sudden warmings (SSWs) can have an impact on the propagation and energy distribution of gravity waves (GWs). The variation characteristics of GWs during SSWs have always been an important issue. Using temperature data from January to March in 2014−2016, provided by the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission, we have analyzed global GW activity at 15−40 km in the Northern Hemisphere during SSW events. During the SSWs that we studied, the stratospheric temperature rose in one or two longitudinal regions in the Northern Hemisphere; the areas affected extended to the east of 90°W. During these SSWs, the potential energy density (\begin{document}$ {E}_{p} $\end{document}) of GWs expanded and covered a larger range of longitude and altitude, exhibiting an eastward and downward extension. The \begin{document}$ {E}_{p} $\end{document} usually increased, while partially filtered by the eastward zonal winds. When zonal winds weakened or turned westward, \begin{document}$ {E}_{p} $\end{document} began to strengthen. After SSWs, the \begin{document}$ {E}_{p} $\end{document} usually decreased. These observations can serve as a reference for analyzing the interaction mechanism between SSWs and GWs in future work.

The intermittency of gravity wave potential energy (GWPE) in the upper troposphere and stratosphere was investigated using the Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) temperature data over three typical mountains (Tibetan Plateau, Rocky Mountains, and Andes). These typical mountains have high sea level elevations but different land–sea contrast. The probability density function (PDF) of GWPE has the independent variable of GWPE and dependent variable of occurrence probability of GWPE over a region. Our analysis showed that the PDFs of GWPE over these three mountains roughly followed lognormal distributions in all heights and months. But, the key parameters (mean value and standard deviation) of lognormal distribution varied with heights and months. Above each mountain, the two key parameters exhibited similar temporal and spatial distributions. They had the largest values around the tropopause region, smaller values in the lower stratosphere (~20–30 km), and larger values in the upper stratosphere (~35–45 km). The intermittency of GWs is represented as the ratio of the GWPE at 50th percentile to the GWPE at 90th percentile. The weakest intermittency was at ~20–30 km (above the zonal mean winds of zero) over the Tibetan Plateau and Rocky Mountains in all months and over the Andes from November to March, respectively. Generally, the weakest intermittency (~0.4) occurred in the region where the key parameters were the smallest around summer. The key parameters of lognormal distribution were dominated by annual variation over the Andes throughout the height range, 8–50 km. However, the semiannual variations are also significant in the lower stratosphere over the Tibetan Plateau and Rocky Mountains. The seasonal variations in the intermittency were not as obvious as those of the key parameters. The lognormal distributions and the intermittencies derived here provide an observational constraint on the tunable parameters in GW parameterization schemes. [ABSTRACT FROM AUTHOR]

This research explores the intricate-coupling relationship between typhoons and the ionosphere by the high-frequency surface wave radar's (HFSWR) over-the-horizon capabilities. This letter describes the gravity wave features in travelling ionospheric disturbances (TIDs) and ionospheric drift information. Further discussion is raised on the chaotic properties of gravity wave features using the Lyapunov exponents and chaotic attractors, particularly as they are influenced by typhoon. To predict these gravity wave features more accurately, a new model is developed by synergizing phase space reconstruction theory and statistical learning theory, a chaotic prediction model for gravity wave features constructed on a third-order Volterra filter. The experimental findings confirm that the gravity waves features detected via HFSWR present the hyperchaotic behaviour. More importantly, the innovative gravity wave prediction model based on chaotic attractor can capture the dynamics of the original chaotic system. Notably, the model's prediction accuracy has been improved by 98.6% after the introduction of phase space reconstruction modelling. [ABSTRACT FROM AUTHOR]

In order to study the scale effect in wave-structure interactions and the role that structure-related parameters (tension T or bending stiffness EI) plays, riser model tests under regular waves were conducted using the model with multiple geometric scales (1:15, 1:12 and 1:9) in a wave basin. The riser model used is a novel structural design combing the outer polyvinyl chloride pipe with the core steel rod which could be simplified as a cantilever beam. Different initial tension T acting on the riser are tested by adjusting the slotted weight. The results show that the amplitude varies in a cubic fashion with the distance from the fixed end. In addition, the influence of the wave period and top tension T on the amplitude are investigated, which ultimately leads to a dimensionless number π1 = KCd·TL²/EI where KC is the classical Keulegan-Carpenter number (KC), EI shows the bending stiffness of the riser model and L gives the pipe length. With the KC number revised to take the distance from the fixed end into the calculation, this parameter provides a good measure in estimating the amplitudes of the riser vibrations induced by the waves. [ABSTRACT FROM AUTHOR]

In this paper, we applied a variety of statistical methods to study gravity waves in the troposphere and lower stratosphere in the Brazilian sector, using a large database from Instituto de Controle do Espaço Aéreo (ICEA) of radiosonde measurements carried out in 2014 at 32 locations in the Brazilian territory totaling 49,652 wind and temperature profiles. The average wind profiles were computed and classified by means of a hierarchical cluster analysis. The kinetic and potential energy densities of gravity waves were determined using a detrending technique based on the Least Squares Method and the Fast Fourier Transform. By analyzing the energy density time series it was found that tropospheric average values are consistently larger in the months of winter, late autumn and early spring. Stratospheric average values of variability and kinetic energy density are also consistently larger in this period. A systematic search for quasi monochromatic waves was carried out and their main characteristics such as horizontal/vertical wavelengths and velocities were determined both in the troposphere and lower stratosphere. A correlation analysis between the troposphere and the lower stratosphere based on the measured parameters was used to investigate the wave coupling between the two layers, and no significant correlation was found. Finally, a spatial correlation analysis between energy densities measured at different aerodromes in the same atmospheric layer was carried out, showing that energy densities are spatially correlated for distances less than 3,000–4,000 km. Plain Language Summary: Like waves in the ocean that can be easily seen by any observer in the beach, the atmosphere is also permeated by waves of similar nature, called Gravity Waves (GWs). These waves transport energy through the atmosphere, eventually breaking, reflecting or dissipating at some point. In this work we investigated the characteristics of these waves using weather data retrieved by weather balloons released from several locations in the Brazilian territory in 2014. By analyzing the measurements, we quantified parameters related to GWs, such as the kinetic and potential energy densities. We also investigated GWs that have well defined frequencies, called monochromatic waves, and determined their wavelengths, phases, amplitudes and phase velocities. We did not find correlations between the wave energies in the troposphere and the low stratosphere, which is an evidence of weak coupling between both layers. This result suggests that GWs characteristics are substantially modified in the perturbed, turbulent and windy region between the troposphere and low stratosphere. Moreover, we also identified the prevailing behavior of the winds in each of the studied locations. Key Points: A comprehensive survey on gravity waves using radiosonde data from 32 locations in the Brazilian territory totaling 49,652 profilesThe energy densities of gravity waves are spatially correlated within a region of approximately 3,000 km of radiusIt was found that gravity waves propagating in the troposphere and low stratosphere are uncorrelated in the studied locations [ABSTRACT FROM AUTHOR]

Space based radio wave communication and navigation has become need of the society. Atmospheric (thermospheric-ionospheric) processes, such as Equatorial Plasma Bubbles (EPBs), affect the radio waves propagating through this region, causing heavy perturbations on signals received at ground. This paper investigates the causative mechanism of EPB through the ground based remotely sensed imaging observations of O (1S) 557.7 nm and O (1D) 630.0 nm emissions emanating from the upper mesosphere (∼100 km altitudes) and thermosphere-ionosphere (∼250 km altitudes) over a low - latitude station, Kolhapur (16.8° N, 74.2° E, and dip lat. 10.6°N). Our investigation revealed that the gravity waves evident in OI557.7 nm images exhibit a close association with the observed EPB structures. These mesospheric gravity waves were found to travel from the South to North with horizontal wavelengths ∼35 and ∼56 km on 13–14 April and 26–27 April 2015, respectively. The thermosphere-ionosphere measurements exhibited occurrence of the North–South aligned EPB moving to the east with an inter depletion distance (IDD) equal to ∼44 km and ∼64 km. These results provide evidences on association of the gravity waves with the EPB. [ABSTRACT FROM AUTHOR]

The impact of mid‐latitude oceanic frontal zones with sharp meridional sea‐surface temperature (SST) gradients on the middle atmosphere circulation during austral winter is investigated by comparing two idealized experiments with a high‐top gravity wave (GW) permitting general circulation model. Control run is performed with realistic frontal SST gradients, which are artificially smoothed in no‐front run. The control run simulates active baroclinic waves and GW generation around the mid‐latitude SST front, with GWs propagating into the stratosphere and mesosphere. In the no‐front run, by contrast, baroclinic‐wave activity is significantly suppressed, and GWs with smaller amplitude are excited and then dissipated at higher altitudes in the mesosphere. Westward wave forcing in the winter hemisphere was more pronounced in the control run up to ∼0.03 hPa, resulting in a more realistic reproduction of the middle atmospheric polar vortex. The results demonstrate the importance of realistic mid‐latitude ocean conditions for simulating the middle atmosphere circulation. Plain Language Summary: The impact of the mid‐latitude oceanic fronts characterized by sharp sea‐surface temperature (SST) gradients is investigated using a global gravity‐wave permitting atmospheric model that represents the troposphere, stratosphere and mesosphere. Two idealized experiments were conducted with different SST profiles. Control run features a realistic SST profile characterized by frontal SST gradients in mid‐latitudes, while they are smoothed out artificially in the "no‐front" run. In winter the no‐front run simulates significantly suppressed generation of synoptic‐scale cyclones and anticyclones, which results in reduced upward propagation of higher‐frequency gravity waves into the stratosphere, exerting marked impact on the large‐scale circulation extending as high as the mesopause. Notably higher gravity wave activity in the control run leads to a weaker, and more realistic wintertime polar vortex in the stratosphere and mesosphere. This study emphasizes the potential influence of mid‐latitude oceanic conditions on the atmospheric circulation, not only in the troposphere but also throughout the stratosphere and mesosphere. Key Points: High‐top global model simulations are conducted to examine the impact of a mid‐latitude oceanic front on the atmospheric circulationThe oceanic front enhances tropospheric baroclinic‐wave activity and generation of gravity waves propagating into the middle atmosphereThe enhanced gravity waves act to reduce cold bias of the wintertime polar vortex in the Southern Hemisphere middle atmosphere [ABSTRACT FROM AUTHOR]

Abstract A new version of NCAR Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension (WACCM‐X) has been developed. The main feature of this version is the species‐dependent spectral element (SE) dynamical core solved on a cubed sphere grid, eliminating the polar singularity and enabling simulations at high‐resolutions. Molecular viscosity and diffusion in the horizontal direction are also included. The Conservative Semi‐Lagrangian Multi‐Tracer Transport Scheme (CSLAM) is employed for the species transport. An efficient regridding scheme based on the Earth System Modeling Framework is used to map fields between the physics mesh and geomagnetic grid. Simulations have been performed at coarse (∼200 km and 0.25 scale height) and high (∼25 km and 0.1 scale height) resolutions. Spatial distribution of the resolved gravity waves from the high‐resolution simulations compares well with available observations in the middle and upper atmosphere. Analysis of the scale dependence of the gravity wave energy density and momentum flux shows that, while larger scale waves are dominant energetically at most latitudes, smaller scale waves contribute significantly to the total momentum flux, especially at mid‐high latitudes. The waves in the thermosphere are shown to be strongly modulated by the large‐scale wind through Doppler shift and molecular damping, and they cause large neutral atmosphere and plasma perturbations.

Upper mesospheric wind data acquired by the medium frequency radar at Kolhapur (16.7oN, 74.2oE) and Modern–Era Retrospective analysis for Research and Application version 2 (MERRA-2) temperature and wind reanalysis datasets are used to investigate the dynamical response of the low-latitude middle atmosphere to the sudden stratospheric warming (SSW) events that occurred during the 2017–18 and 2018–19 winters. When the amplitude of the high-latitude stratospheric planetary wave (PW) of zonal wavenumber one reduces considerably with the onset of the SSW event, the low-latitude mesospheric PW over Kolhapur also shows a considerable reduction in the PW activity. It is noteworthy that the upper mesospheric winds are eastward for approximately 3 weeks after the onset of SSW. The reduced PW activity is associated with the enhanced gravity wave activity in the meridional wind during the SSW 2018–19 event. The plane of propagation of gravity waves obtained from the perturbation ellipse method suggests that their predominant plane of propagation is in the north–south direction. The persistence of the eastward winds is suggested to be due to the interaction of the northward propagating gravity waves with the mean flow, leading to the eastward acceleration due to the Coriolis force.

Using radiosonde and ground mapping data from conventional observations， FNL analysis data （1°×1°） and quality controlled hourly precipitation data of Yunnan regional automatic station， diagnosed the function of the Qinghai-Xizang Plateau’s eastern slope topography in the PLV （plateau vortex） affected precipitation in Yunnan during 2-3 July 2017.While the latest WRFv4.0 numerical model is used to conduct the topographic sensitivity test of this process.The results show that PLV which generated in the Yajiang region of Sichuan province （NO.C1735） is an important system influenced on this heavy rainfall in Yunnan； This low-vortex system maintain warm core structure in the middle and high altitude during the process period， corresponding with remarkable alternately distribution of ascending and descending movements； Distribution of process accumulated rainfall present two obvious NW-SE rain belts parallel to the mountain trend and the precipitation on the rain belt have intensity interlaced fluctuation characteristics； The heavy rainfall mainly occurred within two periods： one from afternoon to evening and other at the first half of the night， and all located besides the terrain slope （the east and south slopes）， especially in areas with steep terrain， large slopes， and trumpet-shaped topography， and then propagates downstream alone with the PLV； The South Asian High， northwest divergent airflow， Western Pacific subtropical high and Yunnan-Myanmar high provides favorable upper flow field for the eastward movement and development of the PLV， besides the position of 500 hPa positive vorticity and 700 hPa water vapor flux convergence can well indicates the heavy rainfall area； There exist β-mesoscale gravity wave during the period of precipitation， which stimulated by the Qinghai-Xizang Plateau’s eastern slope， and propagate between 300~200 hPa； Non geostrophic equilibrium motion and vertical wind shear at high-altitude are beneficial to the occurrence and propagation of gravity wave； The gravity wave propagate downstream before the PLV and precipitation， its wave ridge corresponds to the upward motion and divergence center， whereas the wave trough corresponds to the descending motion and convergence center， the heavy precipitation and the wave ridge are all located at the southwest side of PLV， the area of strong convergence and upward movement； After reduced the terrain height， its mechanical blocking and lifting effect weakened， the gravity wave and PLV disappears， leading to significant changes in the intensity and spatial distribution of the rain belt； Thus， the topography of the eastern slope of the Plateau plays important role both on the formation and development of PLV and precipitation in Yunnan under the influence of PLV.

The high‐resolution Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension (WACCM‐X) is used to study the impacts of gravity waves (GWs) on the thermospheric circulation and composition. The resolved GWs are found to propagate anisotropically with stronger eastward components at most altitudes. The dissipation of these waves in the thermosphere produces a net eastward forcing that reaches peak values between 200 and 250 km at mid‐high latitudes in both hemispheres. Consequently, the mean circulation is weakened in the winter hemisphere and enhanced in the summer, which in turn impacts the thermospheric composition. Most notably, the column integrated O/N2 in both hemispheres is reduced and agrees better with observations. The mean thermospheric GW forcing in the meridional direction has comparable amplitude and acts to modify the gradient‐wind relationship. Plain Language Summary: Small‐scale waves originate from the lower atmosphere have been shown to propagate into the thermosphere. To study their effects a high‐resolution whole atmosphere model has been employed. Using this high‐resolution model, which can partially resolve the small‐scale waves, we can directly quantify the force exerted by these waves on the general circulation in the thermosphere. We found that such force is strong, and affects the thermospheric circulation in both winter and summer hemisphere. This consequently changes the distribution of important thermospheric species. One measure of the thermospheric composition is the ratio of atomic oxygen and molecular nitrogen, which is an indicator of the relative abundance of atomic and molecular species. This ratio has been grossly over‐estimated in previous modeling studies. It is reduced as a result of the circulation change, and is much better agreement with observations. Key Points: Gravity waves (GWs) resolved by high‐resolution WACCM‐X displays anisotropic propagationGW forcing alters thermospheric circulationThe circulation change leads to a much improved thermospheric O/N2 [ABSTRACT FROM AUTHOR]

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As an important means of in situ detection in near space, meteorological rockets can provide a high-precision distribution analysis of atmospheric elements. However, there are currently few studies on the principles of meteorological-rocket detection and the application of rocket-sounding data. The purpose of this paper is to fill this gap by providing a detailed introduction to the detection principle of a meteorological rocket launched in the East China Sea in November 2022. Moreover, empirical models, satellite data, and reanalysis data were selected for comparison and verification with the rocket-sounding data. Furthermore, the accuracy of these widely used datasets was studied based on the rocket-sounding data in the near space over the East China Sea. Additionally, gravity-wave power–frequency spectra were extracted using the maximum entropy method from both the rocket-sounding data and the remote-sensing data. Furthermore, the relationship between gravity waves and Kelvin–Helmholtz instability (KHI) was investigated by analyzing the gravity-wave energy and the Richardson number. The research findings indicate that among the remote-sensing data describing the atmospheric environment over the launch site, the COSMIC occultation data is more accurate compared with the SABER data. The wind-field distribution derived from rocket detection is consistent with the Modern-Era Retrospective analysis for Research and Applications (MERRA) reanalysis data, while also providing a more detailed description of the wind field. The main wavelengths of gravity waves extracted from rocket-sounding data are consistently smaller than those obtained from satellite remote-sensing data, indicating that rocket sounding is capable of capturing more intricate structures of gravity waves. The good correspondence between the peaks of gravity-wave energy and the regions where KHI occurs indicates that there is a strong interaction between gravity waves and KHI in the middle atmosphere. [ABSTRACT FROM AUTHOR]

The temperature plays a critical role in atmospheric research. A measurement system based on Rayleigh scattering Lidar was developed in this study to detect mid and upper-level atmospheric temperature. To analyze the error introduced by the calibration point temperature, the echo signal was simulated. The continuously measured atmospheric temperature structure is stable. The measured atmospheric temperature profile follows the same trend as the atmospheric mode, as shown by comparison with different modes and balloons. The mean difference between the measured atmospheric temperature and the balloon temperature is 2.59 K, with the error mostly concentrated below 5 K. Continuous observation of atmospheric temperature using the system revealed the occurrence of temperature-induced gravity waves at a vertical wavelength from 2 to 3 km at an altitude between 30 and 45 m. Partial fragmentation occurs when energy dissipation is performed in the low-frequency mode from 38 to 45 km. This system was demonstrated to effectively detect temperature and continuously observe gravity waves, with its accuracy confirmed by comparison with balloon temperature measurements. [ABSTRACT FROM AUTHOR]

The cloud imaging and particle size (CIPS) instrument onboard the Aeronomy of Ice in the Mesosphere satellite provides images of gravity waves (GWs) near the stratopause and lowermost mesosphere (altitudes of 50–55 km). GW identification is based on Rayleigh Albedo Anomaly (RAA) variances, which are derived from GW‐induced fluctuations in Rayleigh scattering at 265 nm. Based on 3 years of CIPS RAA variance data from 2019 to 2022, we report for the first time the seasonal distribution of GWs entering the mesosphere with high (7.5 km) horizontal resolution on a near‐global scale. Seasonally averaged GW variances clearly show spatial and temporal patterns of GW activity, mainly due to the seasonal variation of primary GW sources such as convection, the polar vortices and flow over mountains. Measurements of stratospheric GWs derived from Atmospheric InfraRed Sounder (AIRS) observations of 4.3 μm brightness temperature perturbations within the same 3‐year time range are compared to the CIPS results. The comparisons show that locations of GW hotspots are similar in the CIPS and AIRS observations. Variability in GW variances and the monthly changes in background zonal wind suggest a strong GW‐wind correlation. This study demonstrates the utility of the CIPS GW variance data set for statistical investigations of GWs in the lowermost mesosphere, as well as provides a reference for location/time selection for GW case studies. Key Points: Aeronomy of Ice in the Mesosphere cloud imaging and particle size (CIPS) provides first near‐global images of gravity waves at 50–55 km with high horizontal resolutionCIPS observes gravity wave hotspots generated by convection, topography, and the polar vortexLocations of gravity wave hotspots near the stratopause/lowermost mesosphere are similar to those in the mid‐stratosphere near 35 km [ABSTRACT FROM AUTHOR]

The tropopause region is crucial for the stratosphere‐troposphere exchange (STE) and acts as an indicator of climate change. Double tropopauses (DTs) act to increase the STE process but their driving mechanisms remain an open question. The present assessment offers for the first time the linkage between tropospheric gravity waves (GWs) and DT events by exploring a global data set of multi‐year radiosonde measurements. In the extratropics, the occurrence frequency of DT events keeps a remarkably consistent spatial‐temporal structure with GW total energy. Under the DT scenario, GW total energy has increased by 37.67% compared to single tropopause events. Based on a statistical assessment, the upward propagating GWs throughout the second tropopause region can probably raise Kelvin‐Helmholtz instability or turbulence, leading permanent irregularities in thermodynamic structure, and consequently, increasing the likelihood of DT. Plain Language Summary: Atmospheric disturbances above the troposphere are predominantly associated with waves generated in the troposphere. Among others, gravity waves (GWs) play major roles in transport of energy and momentum from the lower to the upper atmosphere. The double tropopause (DT) caused by irregular temperature changes is a common phenomenon in the lowermost stratosphere, which has an indicative significance for climate change. The upward propagating GWs sourced from the troposphere can probably alter the temperature variability in the tropopause region, and therefore, they are likely associated with the occurrence of DTs. By analyzing a large amount of global radiosonde data, simultaneous measurements of tropospheric GWs and irregularities in the tropopause enable us to argue that GWs sourced from troposphere could increase the likelihood of DTs. Key Points: A good level of agreement in spatial‐temporal variability has been identified between Double tropopause (DT) events and tropospheric gravity wave (GW) total energySubstantial tropospheric GW and Kelvin‐Helmholtz instability frequency enhancements in the tropopause region can be observed with DT phenomenaThe tropospheric GWs may increase the likelihood of DT events by introducing permanent localized irregularities or instabilities [ABSTRACT FROM AUTHOR]

Abstract The impact of mid‐latitude oceanic frontal zones with sharp meridional sea‐surface temperature (SST) gradients on the middle atmosphere circulation during austral winter is investigated by comparing two idealized experiments with a high‐top gravity wave (GW) permitting general circulation model. Control run is performed with realistic frontal SST gradients, which are artificially smoothed in no‐front run. The control run simulates active baroclinic waves and GW generation around the mid‐latitude SST front, with GWs propagating into the stratosphere and mesosphere. In the no‐front run, by contrast, baroclinic‐wave activity is significantly suppressed, and GWs with smaller amplitude are excited and then dissipated at higher altitudes in the mesosphere. Westward wave forcing in the winter hemisphere was more pronounced in the control run up to ∼0.03 hPa, resulting in a more realistic reproduction of the middle atmospheric polar vortex. The results demonstrate the importance of realistic mid‐latitude ocean conditions for simulating the middle atmosphere circulation.

Atmospheric gravity waves (GWs) can strongly modulate middle atmospheric circulation and can be a significant factor for the coupling between the lower atmosphere and the middle atmosphere. GWs are difficult to resolve in global atmospheric models due to their small scale; thus, GW observations play an important role in middle atmospheric studies. The climatology of GW variance and momentum in the low-latitude mesosphere and lower thermosphere (MLT) region are revealed using multiple meteor radars, which are located at Kunming (25.6°N, 103.8°E), Sanya (18.4°N, 109.6°E), and Fuke (19.5°N, 109.1°E). The climatology and longitudinal variations in GW momentum fluxes and variance over the low-latitude region are reported. The GWs show strong seasonal variations and can greatly control the mesospheric horizontal winds via modulation of the quasi-geostrophic balance and momentum deposition. The different GW activities between Kunming and Sanya/Fuke are possibly consistent with the unique prevailing surface winds over Kunming and the convective system over the Tibetan Plateau according to the European Centre for Medium-Range Weather Forecasts (ECMWF), Reanalysis v5 (ERA5) data, and outgoing longwave radiation (OLR) data. These findings provide insight for better understanding the coupling between the troposphere and mesosphere.

Gravity wave (GW) momentum flux spectra help to uncover the mechanisms through which GWs influence momentum transfer in the atmosphere and provide crucial insights into accurately characterizing atmospheric wave processes. This study examines the momentum flux spectra of GWs in the troposphere (2–14 km) and stratosphere (18–28 km) over Koror Island (7.2°N, 134.3°W) using radiosonde data from 2013–2018. Utilizing hodograph analysis and spectral methods, the characteristics of momentum flux spectra are discussed. Given that the zonal momentum flux spectra of low-level atmospheric GWs generally follow a Gaussian distribution, Gaussian fitting was applied to the spectral structures. This fitting further explores the seasonal variations of the zonal momentum flux spectra and the average spectral parameters for each month. Additionally, the GW energy is analyzed using SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite data and compared with the results of the momentum flux spectra from radiosonde data, revealing the close negative correlation between wave energy and wave momentum for stratospheric GW changing with time. The findings indicate that the Gaussian peak shifts more eastward in both the troposphere and stratosphere, primarily due to the absorption of eastward-propagating GWs by the winter tropospheric westerly jet and critical layer filtering. The full width at half maximum (FWHM) in the stratosphere is larger than in the troposphere, especially in June and July, as the spectrum broadens due to propagation effects, filtering, and interactions among waves. The central phase speed in the stratosphere exceeds that in the troposphere, reflecting the influences of Doppler effects and background wind absorption. The momentum flux in the stratosphere is lower than in the troposphere, which is attributed to jet absorption, partial reflection, or the dissipation of GWs.

Cirrus clouds play a significant role in Earth's energy balance and in the hydrological cycle of the atmosphere.In this study， we focus on the period of several years， 2007 to 2010， and the area， the Qinghai-Xizang Plateau， to analyze the generation mechanism and the distribution characteristics of cirrus clouds by using the data of “Cloud Satellite” （CLOUDSAT） and “Cloud-Aerosol Lidar and Infrared Pathfinder Satellite” （CALIPSO）.Counting the number of the occurrence of cirrus clouds in different height， including high-level cirrus clouds and low-level cirrus clouds， the results show that the total occurrence frequency of high-level cirrus clouds is much higher than that of low-level cirrus clouds during the selected period and area.High-level cirrus clouds usually occur in the southern part of the plateau， and low-level cirrus clouds have much occurrence frequency both at the edge of the plateau and in the western part of the plateau.Besides， when calculating the loss of the gravitational wave， the result also shows an important relationship between the gravitational wave and the occurrence frequency of low-level cirrus clouds， that they are positively correlated with each other.To be specific， the larger the gravitational wave loss， the more cirrus clouds occur.The reason why this phenomenon occurs is that the formation of cirrus clouds in the plateau area is closely related to the temperature disturbance which is caused by the gravitational wave.By investigating in the selected area， there is the phenomenon that the deep convection mostly occurs in the southeast of the Qinghai-Xizang Plateau and the following conclusions can be drawn： When the outward longwave radiation （OLR） is lower than 140 W·m-2， that is， the deep convection activity is the strongest， the daily occurrences frequency of high-level cirrus clouds grows explosively， being much higher than the northern and western regions of the plateau.In addition， on southern edge of the Qinghai-Xizang Plateau， cirrus clouds not only are influenced by the deep convection， but also are closely related the water vapor content and vertical upward wind speed， which shows a decreasing trend from south to north.All the phenomenon on southern edge of the Qinghai-Xizang Plateau is directly related to the elevation of terrain in the plateau.

Abstract The high‐resolution Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension (WACCM‐X) is used to study the impacts of gravity waves (GWs) on the thermospheric circulation and composition. The resolved GWs are found to propagate anisotropically with stronger eastward components at most altitudes. The dissipation of these waves in the thermosphere produces a net eastward forcing that reaches peak values between 200 and 250 km at mid‐high latitudes in both hemispheres. Consequently, the mean circulation is weakened in the winter hemisphere and enhanced in the summer, which in turn impacts the thermospheric composition. Most notably, the column integrated O/N2 in both hemispheres is reduced and agrees better with observations. The mean thermospheric GW forcing in the meridional direction has comparable amplitude and acts to modify the gradient‐wind relationship.

Abstract The cloud imaging and particle size (CIPS) instrument onboard the Aeronomy of Ice in the Mesosphere satellite provides images of gravity waves (GWs) near the stratopause and lowermost mesosphere (altitudes of 50–55 km). GW identification is based on Rayleigh Albedo Anomaly (RAA) variances, which are derived from GW‐induced fluctuations in Rayleigh scattering at 265 nm. Based on 3 years of CIPS RAA variance data from 2019 to 2022, we report for the first time the seasonal distribution of GWs entering the mesosphere with high (7.5 km) horizontal resolution on a near‐global scale. Seasonally averaged GW variances clearly show spatial and temporal patterns of GW activity, mainly due to the seasonal variation of primary GW sources such as convection, the polar vortices and flow over mountains. Measurements of stratospheric GWs derived from Atmospheric InfraRed Sounder (AIRS) observations of 4.3 μm brightness temperature perturbations within the same 3‐year time range are compared to the CIPS results. The comparisons show that locations of GW hotspots are similar in the CIPS and AIRS observations. Variability in GW variances and the monthly changes in background zonal wind suggest a strong GW‐wind correlation. This study demonstrates the utility of the CIPS GW variance data set for statistical investigations of GWs in the lowermost mesosphere, as well as provides a reference for location/time selection for GW case studies.

Abstract The tropopause region is crucial for the stratosphere‐troposphere exchange (STE) and acts as an indicator of climate change. Double tropopauses (DTs) act to increase the STE process but their driving mechanisms remain an open question. The present assessment offers for the first time the linkage between tropospheric gravity waves (GWs) and DT events by exploring a global data set of multi‐year radiosonde measurements. In the extratropics, the occurrence frequency of DT events keeps a remarkably consistent spatial‐temporal structure with GW total energy. Under the DT scenario, GW total energy has increased by 37.67% compared to single tropopause events. Based on a statistical assessment, the upward propagating GWs throughout the second tropopause region can probably raise Kelvin‐Helmholtz instability or turbulence, leading permanent irregularities in thermodynamic structure, and consequently, increasing the likelihood of DT.

The uneven distribution of GNSS observations and the scarcity of satellite data pose challenges for the continuous detection of traveling ionospheric disturbances (TIDs) induced by gravity waves (GWs). This paper proposes a short-term TID forecasting method based on the convolutional long short-term memory (ConvLSTM) neural network. This method utilizes 3-D electron density disturbance information from 3-dimensional computerized ionospheric tomography (3DCIT) results to predict the 3-D characteristics of ionospheric disturbances during Hurricane Matthew. A multi-channel forecasting pattern combining disturbance feature labels is used to improve the forecast accuracy. The results show that the ConvLSTM network can effectively identify the spatiotemporal features of TIDs. The inclusion of the labels greatly enhances the forecast performance, as shown by the reduction of the mean absolute error (MAE) and root mean square error (RMSE) over longer forecast durations, along with the increase in correlation. Additionally, the horizontal phase velocities of the TIDs at 200 and 300 km altitudes calculated using the 5-minute forecast results (∼150-173.33 m/s) are comparable to the original 3DCIT estimation (∼166.67-170 m/s). [ABSTRACT FROM AUTHOR]

We report for the first time a case of wavelike structures of E‐region irregularities observed by an all‐sky radar at Ledong (18.44°N, 108.97°E), China. The wavelike structures covered up to 250 km zonally, fluctuated in the vertical and horizontal planes, and were observed in the directions perpendicular and significantly off‐perpendicular to the geomagnetic field. The wavelength, and vertical and horizontal oscillating amplitudes were estimated at about 20–70, 5, and 2 km, respectively. Eventually, the large‐scale wavelike structure broke into spatially separated small‐scale patches and disappeared. The case provides observational evidence for the wave modulating sporadic E (Es) mechanism, which suggests that the wavelike structures of E‐region irregularity were primarily generated by wind shears and modulated by gravity waves. The wavelike structure was possibly an intermediate state between the continuous‐type and quasiperiodic‐type E‐region irregularities. The mechanism responsible for the echoing structure observed in off‐perpendicular directions is unclear. The possible contributions from refraction and reflection by intense Es layer/structure were discussed. Plain Language Summary: The E‐region irregularities were usually observed using narrow‐beam very high frequency radars. Due to the limited field‐of‐view (FOV) of the narrow‐beam radars, the spatial morphology of large‐scale irregularity structures could not be obtained. Over low latitudes, the E‐region irregularities were traditionally classified into two main types: the continuous type linked with the tidal sporadic E (Es) layer and the quasiperiodic (QP) type due to the drift of small irregularity patches. Facilitating from the very large FOV of the all‐sky radar at Ledong, we report a case of E‐region irregularities with different echo patterns from the continuous and the QP types. These E‐region irregularities showed wavelike structures covering up to 250 km in the zonal direction and were observed in directions both perpendicular and significantly off‐perpendicular to the geomagnetic field. In combination with the collocated Es and neutral wind measurements, the possible mechanisms responsible for the wavelike irregularity structures are discussed. Key Points: Wavelike structures of E‐region irregularities elongating up to 250 km are reported at low latitudes for the first timeThe wavelike structures were most likely generated by wind shears and modulated by gravity wavesThe wavelike structures may be an intermediate state between the continuous‐type and quasiperiodic‐type E‐region irregularities [ABSTRACT FROM AUTHOR]

All known planets orbit the Sun so harmoniously that the entire Universe is believed to behave in a rhythmical and fractal way. Titius–Bode law is the main theoretical tool for planetary orbit description. Here we show that planetary sequence follows the Fibonacci-like prime sequence, and we introduce two gravitational spirals to predict orbits for solar members orbiting the Sun. Furthermore, we predict two hypothetical planets as far as 1500 AU and 2300 AU from the Sun, respectively, in our solar system, and some unknown planets in extrasolar planetary systems. Our planetary sequence demonstrates the possible frontier of our solar system, and the theory is also valid for other star systems and planetary systems, giving a simple way to finding the most possible adjacent unknown planets or moons near a known one. We anticipate our sequence can be more sophisticatedly used to search for unknown Universes and to depict the cosmos fully and exclusively, and we conclude that our whole Universe is of fractal property and all celestial bodies are distributed according to Fibonacci sequence. [ABSTRACT FROM AUTHOR]

Cold pools that form from existing convection can generate new clouds nearby, a process that has been suggested to contribute to cloud organization. However, some disagreement exists on the role of cold pools in cloud organization over tropical oceans, and much remains to be understood on how this role depends on the state of large‐scale disturbances such as the Madden‐Julian Oscillation (MJO). This study addresses this question by examining the intraseasonal variability in the properties of cold pools and their effects on convection triggering using observations. The unique set of surface meteorology data and ground‐based radars deployed during the DYNAMO/AMIE field campaign are used to identify cold pools and the associated spatiotemporal evolution of rainfall. The results suggest that cold pools enhance rainfall at their expected speed of 3–8 m s−1, which includes the Doppler‐shifting effect by the background wind. The cold pools also enhance rainfall mainly within a 20 km radius, especially in the direction of boundary‐layer vertical wind shear. However, gravity waves appear to contribute predominantly to the propagation of convection over a wider range of distances due to their faster propagation speeds. The interface of convection triggering and propagation at different speeds of cold pools and gravity waves seems to contribute to cloud organization. The effectiveness of cold pools and gravity waves on cloud organization also depends highly on the MJO due to the combined effects of changes in environmental humidity and boundary to lower‐tropospheric wind. Plain Language Summary: High‐density air that forms due to evaporative cooling of rainfall and downward injection of colder air aloft spreads horizontally, a phenomenon known as a cold pool. The spreading edges of cold pools initiate new cumulus clouds by lifting humid air, which is thought to cluster cumulus clouds that can merge and form larger clouds. However, the importance of cold pools in cloud clustering remains debated. This study uses a unique combination of observational data collected during a field campaign deployed over the Indian Ocean to examine the effect of cold pools on cloud clustering. The results provide observational evidence that cold pools support cloud formation within a 20 km radius of the identified cold pools, helping the clustering of clouds within a limited distance. In addition to cold pools, gravity waves that form from cumulus clouds mainly lead to the propagation and formation of cumulus clouds over longer distances due to their faster propagation speeds. The formation of cumulus clouds over a varying range of distances due to different propagation speeds of cold pools and gravity waves seems critical to the clustering of clouds. However, their effectiveness on cloud formation depends on atmospheric conditions set by intraseasonal variability. Key Points: Precipitation‐induced cold pools are observed to enhance rainfall within 20 km through interactions with boundary‐layer vertical wind shearWhile cold pools trigger convection within a limited distance, gravity waves mainly propagate convection over a wider range of distancesThe cold pools and gravity waves together lead to cloud organization, but their effectiveness depends on the large‐scale environment [ABSTRACT FROM AUTHOR]

Abstract Using an atmosphere–ionosphere coupled model (GAIA), atmospheric and ionospheric perturbations triggered by the 2022 Hunga-Tonga volcanic eruption are studied. Our result shows that ionospheric perturbations are caused by neutral wind perturbations associated with gravity waves. Gravity waves with horizontal phase speeds of 200–310 m/s are excited in the troposphere near the Hunga-Tonga volcano, and propagate upward into the thermosphere. While the amplitude of the eruption-generated gravity waves is small in the troposphere (~ 1 m/s), the amplitude of the gravity waves increases exponentially with height because of the exponential decrease of the density, reaching 60‒80 m/s at 300 km height. General features of the TIDs appeared in GNSS–TEC observations reported in earlier studies are reproduced fairly well. We can conclude that the eruption-generated gravity waves whose horizontal phase velocity is close to the sound speed play an important role in thermospheric and ionospheric perturbations after the Hunga-Tonga volcano eruption. Graphical Abstract

The intermittency of gravity wave potential energy (GWPE) in the upper troposphere and stratosphere was investigated using the Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) temperature data over three typical mountains (Tibetan Plateau, Rocky Mountains, and Andes). These typical mountains have high sea level elevations but different land–sea contrast. The probability density function (PDF) of GWPE has the independent variable of GWPE and dependent variable of occurrence probability of GWPE over a region. Our analysis showed that the PDFs of GWPE over these three mountains roughly followed lognormal distributions in all heights and months. But, the key parameters (mean value and standard deviation) of lognormal distribution varied with heights and months. Above each mountain, the two key parameters exhibited similar temporal and spatial distributions. They had the largest values around the tropopause region, smaller values in the lower stratosphere (~20–30 km), and larger values in the upper stratosphere (~35–45 km). The intermittency of GWs is represented as the ratio of the GWPE at 50th percentile to the GWPE at 90th percentile. The weakest intermittency was at ~20–30 km (above the zonal mean winds of zero) over the Tibetan Plateau and Rocky Mountains in all months and over the Andes from November to March, respectively. Generally, the weakest intermittency (~0.4) occurred in the region where the key parameters were the smallest around summer. The key parameters of lognormal distribution were dominated by annual variation over the Andes throughout the height range, 8–50 km. However, the semiannual variations are also significant in the lower stratosphere over the Tibetan Plateau and Rocky Mountains. The seasonal variations in the intermittency were not as obvious as those of the key parameters. The lognormal distributions and the intermittencies derived here provide an observational constraint on the tunable parameters in GW parameterization schemes.

Data acquired by broadband seismic stations distributed around the world are used to document the exceptionally long duration signal from the tsunami-associated gravity wave that followed the January 2022 Hunga-Tonga eruption. The first arrivals of this wave, with a frequency of around 2 mHz, are recorded at the time the tsunami arrives to each station, but the highest recorded frequencies, which reach 40 mHz, arrive 5 days later at some sites, following the prediction of a gravity wave originating at the Hunga-Tonga region and traveling in deep water. This dispersive signal is detected in most of the stations located in the Pacific Ocean basin and its coasts, but also in the Indian Ocean, Antarctica, and some stations in North America located hundreds of kilometers from the coastline. The signal is compared with the data gathered after earthquakes that have produced large tsunamis, showing that the seismic records from the Hunga-Tonga eruption are very different. Following the hypothesis pointed out by Omira et al 2023, we propose that the origin of this exceptional characteristic is due to the interaction between the tsunami and atmospheric waves that travel a little faster.

Lidar observations are an effective tracker for identifying atmospheric wave signals. In this research, observations through three lidars are utilized to study the wave structures. A broadband sodium fluorescence lidar and a narrowband Temperature/Wind (T/W) lidar located at Hefei (31.8°N, 117.3°E), while the third lidar system, a broadband lidar system, is located in Wuhan (30.5°N, 114.4°E), about 310 km from Hefei. The three lidars can observe sodium density, temperature and wind profiles simultaneously. Joint sodium density measurements by the fourth lidar beams from Wuhan and Hefei yield a peculiar NaS with distinguished C‐structure and a large horizontal scale of wave structure over more than 310 km, on 21 December 2014. The NaS event occurring at 14:20 to 17:50 UT corresponds well to the region where the Richardson Number (Ri) is larger than 10, which in turn indicates that the NaS was formed in an extremely stable atmosphere. Results from the Lomb‐Scargle periodogram analysis suggest that the occurrence and evolution of this NaS event may have been caused by a gravity wave with a period of about 1.25 hr, and its end is closely related to the gravity wave fragmentation caused by convective instability. Plain Language Summary: The sporadic sodium layer (SSLs or NaS) is the most fascinating phenomenon observed from the mesospheric layer. On 21 December 2014, a peculiar NaS, exhibiting distinguished C‐structure and wave characteristics, was observed by four lidar beams, which came from a sodium fluorescence lidar and a temperature and wind (T/W) lidar at Hefei and a sodium fluorescence lidar at Wuhan. The NaS event corresponds well to the region where the Richardson Number (Ri) is larger than 10, which indicates that this event was formed in an extremely stable atmosphere. Results from the Lomb‐Scargle spectral analysis and instability analysis suggest that the occurrence of this NaS is closely related to the propagation and breaking of gravity waves. Key Points: Joint measurements by four lidar beams exhibit a peculiar NaS with distinguished C‐shape and wave structure of large horizontal scaleThe NaS corresponds well to the region where the Ri is persistently larger than 10, indicating an extremely stable state of the mesopauseResults from Lomb‐Scargle analysis suggest the occurrence of the NaS caused by a gravity wave, and its end related to the wave breaking [ABSTRACT FROM AUTHOR]

Gravity waves (GWs) and their associated multi‐scale dynamics are known to play fundamental roles in energy and momentum transport and deposition processes throughout the atmosphere. We describe an initial machine learning model—the Compressible Atmosphere Model Network (CAM‐Net). CAM‐Net is trained on high‐resolution simulations by the state‐of‐the‐art model Complex Geometry Compressible Atmosphere Model (CGCAM). Two initial applications to a Kelvin‐Helmholtz instability source and mountain wave generation, propagation, breaking, and Secondary GW (SGW) generation in two wind environments are described here. Results show that CAM‐Net can capture the key 2‐D dynamics modeled by CGCAM with high precision. Spectral characteristics of primary and SGWs estimated by CAM‐Net agree well with those from CGCAM. Our results show that CAM‐Net can achieve a several order‐of‐magnitude acceleration relative to CGCAM without sacrificing accuracy and suggests a potential for machine learning to enable efficient and accurate descriptions of primary and secondary GWs in global atmospheric models. Plain Language Summary: Atmospheric gravity waves (GWs) are well described by the Navier‐Stokes equations, but solving these equations including small scale remains daunting, limited by the very high computational cost of resolving the smallest spatial‐temporal features in a global context. To address this challenge, we developed a machine learning model called CAM‐Net. Our model demonstrates that neural networks can be trained on high‐resolution compressible atmospheric model data and then used to simulate GW evolution. Importantly, initial results show that using such trained model can achieve computational savings of >1,000 times compared to a physics‐based simulation while still achieve highly accurate results. These findings are exciting, as they suggest that CAM‐Net can overcome the limitations of current GW parameterizations and provide a promising avenue for studying the effects of sub‐grid‐scale processes in atmospheric science and properly incorporating them in global models. The development of CAM‐Net opens up major new opportunities for improving effective model resolution, accuracy, and efficiency. Key Points: A machine learning model (CAM‐Net) tailored for nonlinear Gravity wave (GW) simulations is developedCAM‐Net can achieve a several order‐of‐magnitude acceleration relative to physics‐based model without sacrificing accuracyCAM‐Net opens a new window to improve the parameterization of primary and secondary GWs in the global atmospheric models [ABSTRACT FROM AUTHOR]

Based on several kinds of observational data and numerical simulation, the mesoscale features of a strong squall line on March 19, 2013, in southern China were investigated. The results show that: (1) The squall line occurred in front of a 500-hPa trough and was near a cold front on the ground. The ambient wind was mainly southwestern, and its cross-line component was smaller than the along-line component. (2) There were significant differences between the east and the west of the squall line. The eastern part was dry, and the DCAPE was large; as a result, short-term heavy rainfall was weaker than that in the western part, while thunderstorm gales were stronger. Convective cells in the eastern part initially distributed in a fragmented manner at the cold side of the frontal zone. The western part was humid, with short-term heavy rainfall and concentrated hail. Convective cells appeared within the mesoscale convergence line near the surface front area, and the convergence line was persistent. There are constantly new cells growing at the convergence center above them. (3) The gravity waves affected the maintenance of the squall line, and their effect in the western part was obviously stronger than that in the eastern part. When the updraft of the jet intersected with the convergent line, the lower-level updraft at the intersection strengthened and led to convective initiation (CI). Finally, the squall line formed along the amplitude of the gravity waves. (4) New convective cells emerged in both the north and the south of older cells. The upper and lower gravity waves of those new cells in the north were out of phase, restraining the convection; however, they were in phase in the southern new cells, which positively contributed to CI. New cells continued to emerge and replaced old ones, and the squall line propagated to the southeast. [ABSTRACT FROM AUTHOR]

Atmospheric gravity waves (AGWs) and medium‐scale traveling ionospheric disturbances (MSTIDs) in the upper atmosphere can be observed in nocturnal airglow images. Spectral analysis of airglow images provides propagation direction and intensity of these waves. However, the spectral analysis of airglow images has not been done yet for stations in the southern hemisphere except for Antarctica. In this study, we calculated the horizontal phase velocity spectra of AGWs in the mesosphere‐lower‐thermosphere (MLT) region near the mesopause and MSTIDs in the F‐region ionosphere from airglow images at wavelengths of 557.7 and 630.0 nm, respectively, by applying the 3‐dimensional Fourier spectral analysis to the airglow images obtained at Darwin (12.4°S, 131.0°E) in Australia for 13.75 years from 2001 to 2007 and from 2011 to 2019. The spectra of AGWs in the MLT region show clear characteristics that the southward power spectral density (PSD) is stronger in summer and weaker in winter. Tropospheric convection was located at north of Darwin in summer and above Darwin in winter, suggesting that the tropospheric convection is a possible source of AGWs in the mesopause region. The spectra of MSTIDs in the F‐region ionosphere show that the dominant northwestward PSD is stronger in winter and during solar quiet periods. These features can be explained if the observed MSTIDs are caused by the ionospheric instabilities. A weak positive correlation was observed between PSDs of AGWs in the mesosphere and MSTIDs. We propose that the MSTIDs propagating other than northwestward may be generated by AGWs. Plain Language Summary: Atmospheric gravity waves (AGWs) and medium‐scale traveling ionospheric disturbances (MSTIDs) in the upper atmosphere affect the atmospheric circulation and radio‐wave transmissions, including satellite positioning. These waves can be observed in nocturnal airglow images. Thus, spectral analysis of airglow images provides propagation direction and intensity of these waves. However, such spectral analysis of airglow images has not been done yet for stations in the southern hemisphere except for Antarctica. In this study, we calculated the horizontal phase velocity spectra of AGWs and MSTIDs from airglow images at wavelengths of 557.7 and 630.0 nm, respectively, by applying the 3‐dimensional Fourier spectral analysis to the airglow images obtained at Darwin in Australia for 13.75 years from 2001 to 2007 and from 2011 to 2019. The southward propagating AGWs are stronger in summer and weaker in winter. We suggest that the tropospheric convection is a possible source of these AGWs. The northwestward MSTIDs are stronger in winter and during solar quiet periods. These features can be explained if the observed dominant northwestward MSTIDs are caused by the ionospheric instabilities, although other directions may be caused by AGWs. Key Points: We obtained the horizontal phase velocity distribution of airglow waves seen in 557.7 and 630.0‐nm images at Darwin over 13.75 yearsTropospheric convection is a possible source of atmospheric gravity waves (AGWs) seen in 557.7‐nm airglow images in the mesopause regionMedium‐scale traveling ionospheric disturbances in 630.0‐nm images are caused not only by the ionospheric instabilities, but also by AGWs [ABSTRACT FROM AUTHOR]

Past studies have indicated that precipitation over tropical open oceans generally peaks in the early morning. However, an intriguing departure from this pattern is observed in the central Bay of Bengal (CBoB), where rainfall exhibits a distinct afternoon peak during the South Asian summer monsoon season. By using a novel satellite‐based cloud classification and tracking data set, we found that more than 75% of the afternoon rainfall (15–17 LST) over the CBoB comes from mesoscale convective systems (MCSs). Most of the MCSs contributing to the CBoB afternoon rainfall peak originate either locally over the CBoB or near the west and east coasts of the BoB, in contrast to the northern BoB as highlighted in previous studies. Analyses show that MCSs initiated near coastlines are primarily influenced by land‐sea breezes, whereas MCSs initiated over the BoB open ocean during early morning are strongly associated with diurnal radiative forcings. In addition, there are clear diurnal propagating MCS initiation signals from the west and north coastlines of the BoB to the CBoB, which are related to diurnal gravity waves emitted from the coastlines. The thermodynamic conditions conducive to MCS initiation over different sub‐regions of the BoB are also investigated. No systematic differences found in environmental convective available potential energy between days with and without MCS initiation. However, over most sub‐regions, days with MCS initiation generally have higher total column water vapor than days without MCS initiation. This difference suggests that the lower‐free‐tropospheric moisture content plays an important role in MCS initiation over the BoB. Plain Language Summary: Precipitating clouds over tropical oceans play a major role in Earth's water and energy cycles. Their precipitation generally peak in the early morning due to the diurnal changes of solar radiation. However, previous studies indicated that the summertime rainfall over the central Bay of Bengal (BoB) shows a prominent peak in the afternoon. Using satellite data, we found that this afternoon rainfall peak is mainly attributed to large, intense, and organized cloud systems. These cloud systems usually initiate near the BoB coastlines or over the BoB open oceans. Diurnal variations of land‐sea breezes, radiation, and atmospheric gravity waves contribute to the initiation of these systems. Additionally, atmospheric moisture may play as a dominant factor that determines the occurrence of these large cloud systems. These findings might be helpful to the future development of global climate models to simulate the diurnal cycle of rainfall more accurately over the BoB. Key Points: More than 75% of afternoon rainfall over the central Bay of Bengal comes from mesoscale convective systems (MCSs)These MCSs are initiated over either the coastal or open ocean due to the diurnal land‐sea breezes, radiative effects, and gravity wavesThe lower‐free‐tropospheric moisture content plays an important role in MCS initiation over the Bay of Bengal [ABSTRACT FROM AUTHOR]

The satellite‐based Cloud Imaging and Particle Size (CIPS) instrument and Atmospheric Infrared Sounder (AIRS) observed concentric gravity waves (GWs) generated by Typhoon Yutu in late October 2018. This work compares CIPS and AIRS nadir viewing observations of GWs at altitudes of 50–55 and 30–40 km, respectively, to simulations from the high‐resolution European Centre for Medium‐Range Weather Forecasting Integrated Forecasting System (ECMWF‐IFS) and ECMWF reanalysis v5 (ERA5). Both ECMWF‐IFS with 9 km and ERA5 with 31 km horizontal resolution show concentric GWs at similar locations and timing as the AIRS and CIPS observations. The GW wavelengths are ∼225–236 km in ECMWF‐IFS simulations, which compares well with the wavelength inferred from the observations. After validation of ECMWF GWs, five category five typhoon events during 2018 are analyzed using ECMWF to obtain characteristics of concentric GWs in the Western Pacific regions. The amplitudes of GWs in the stratosphere are not strongly correlated with the strength of typhoons, but are controlled by background wind conditions. Our results confirm that amplitudes and shapes of concentric GWs observed in the stratosphere and lowermost mesosphere are heavily influenced by the background wind conditions. Plain Language Summary: Atmospheric gravity waves (GWs) have an important role in coupling the different atmospheric layers. One of the main sources of GWs is convection such as typhoons. In the stratosphere, these GWs frequently appear as concentric (or ring‐shaped) patterns in nadir‐viewing satellite measurements. In this work, data from two such nadir viewing satellite instruments, the Cloud Imaging and Particle Size (CIPS) instrument and Atmospheric Infrared Sounder (AIRS), are analyzed to study the GWs generated by Typhoon Yutu, which occurred in late October 2018. CIPS and AIRS observe at altitudes of 50–55 and 30–40 km, respectively, providing us a unique opportunity to study concentric GWs at two different altitudes. The satellite observations are then used to validate the GW‐resolving high‐resolution European Centre for Medium‐Range Weather Forecasting (ECMWF) model. Utilizing ECMWF simulations, four more typhoon events were analyzed. The results indicate that the amplitudes of concentric GWs in the stratosphere are not correlated with the strength of typhoons. However, the amplitudes and shapes of concentric GWs observed in the stratosphere and lower mesosphere are found to be influenced by the background wind conditions. This work provides an understanding of the relative importance of GW source strength and background wind conditions. Key Points: Cloud Imaging and Particle Size (CIPS) and Atmospheric Infrared Sounder (AIRS) measurements of concentric gravity waves (GWs) generated by Typhoon Yutu are used to verify European Centre for Medium‐Range Weather Forecasting (ECMWF) GWs in the altitude range of 30–55 kmAnalysis of GW observations from CIPS and AIRS as well as ECMWF data provides detailed characteristics of concentric GWsDifferences in GW amplitudes among five typhoon cases grow as GWs propagate upward, indicating the importance of background winds [ABSTRACT FROM AUTHOR]

A new Cloud Imaging and Particle Size (CIPS) gravity wave (GW) variance data set is available that facilitates automated analysis of GWs entering the mesosphere. This work examines several years of CIPS GW variances from 50 to 55 km in the context of the Arctic and Antarctic polar vortices. CIPS observes highest GW activity in the vortex edge region where horizontal wind speeds are largest, consistent with previously published GW climatologies in the stratosphere and mesosphere. CIPS observes the well‐documented planetary wave (PW)‐1 patterns in GW activity in both hemispheres. In the Northern Hemisphere, maximum GW activity occurs over the North Atlantic and western Europe. In the Southern Hemisphere, maximum GW activity stretches from the Andes over the South Atlantic and Indian Oceans, as expected. In the NH, CIPS GW spatial patterns are highly correlated with horizontal wind speed. In the SH, CIPS GW patterns are less positively correlated with the winds due to increased zonal symmetry and orographic forcing. The Andes Mountains and Antarctic Peninsula, South Georgia Island, Kerguelen/Heard Islands, New Zealand, and Tasmania are persistent sources of orographic GWs. Atmospheric Infrared sounder observations of stratospheric GWs are analyzed alongside CIPS to explore vertical GW coherence and to infer GW propagation and sources. NH midlatitude GW activity is reduced during the January 2021 SSW, as expected. This reduction in GWs leads to a simultaneous reduction in traveling ionospheric disturbances (TIDs), providing more evidence that weak polar vortex events with weak GW activity leads to reduced daytime TID activity. Plain Language Summary: A new satellite gravity wave (GW) variance data set is available that facilitates automated analysis of GWs entering the mesosphere. This work examines several years of GW variances from 50 to 55 km in the context of the Arctic and Antarctic polar vortices. Highest GW activity is observed in the vortex edge region where horizontal wind speeds are largest, consistent with previous work. Known planetary wave‐1 patterns are confirmed in the new data set. In the Northern Hemisphere, maximum GW activity occurs over the North Atlantic and western Europe. In the Southern Hemisphere, maximum GW activity stretches from the Andes over the South Atlantic and Indian Oceans. In the Arctic winter, GW spatial patterns are highly correlated with horizontal wind speed. In the Antarctic winter, GW patterns are less positively correlated with the winds due to smaller variations around a latitude circle and larger orographic forcing. We show that Arctic midlatitude GW activity is reduced during the January 2021 SSW, as expected. This reduction in GWs leads to a simultaneous reduction in traveling ionospheric disturbances (TIDs), providing more evidence that weak polar vortex events with weak GW activity leads to reduced daytime TID activity. Key Points: This is the first work to present gravity waves (GWs) from 50 to 55 km observed by AIM CIPS with a focus on the winter polar vorticesDuring the 2020–2021 Arctic winter the longitude of maximum GW activity, maximum horizontal wind speed, and the polar vortex are co‐locatedReduced GW activity during the January 2021 SSW leads to simultaneous reductions in daytime traveling ionospheric disturbances [ABSTRACT FROM AUTHOR]