Near-ground Atmosphere Research Articles

Occurrence frequency of subcritical Richardson numbers assessed by global high-resolution radiosonde and ERA5 reanalysis

Abstract. Kelvin–Helmholtz instability (KHI) is most likely to be the primary source for clear-air turbulence, which is of importance in pollution transfer and diffusion and aircraft safety. It is indicated by the critical value of the dimensionless Richardson (Ri) number, which is predicted to be 1/4 from linear stability analysis. However, Ri is fairly sensitive to the vertical resolution of the dataset; a higher resolution systematically leads to a finer structure. The study aims to evaluate the performance of ERA5 reanalysis in determining the spatial–temporal variabilities in subcritical Ri by comparing it against a near-global high-resolution radiosonde dataset during the years 2017 to 2022 and further highlights the global climatology and dynamical environment of subcritical Ri. Overall, the occurrence frequency of Ri<1/4 is inevitably underestimated by the ERA5 reanalysis over all climate zones at all heights from the near-ground atmosphere up to 30 km, compared to radiosonde, due directly to the severe underestimation in wind shears. Otherwise, the occurrence frequency of Ri<1 in ERA5 is climatologically consistent with that from Ri<1/4 in radiosondes in the free troposphere, especially over the midlatitude and subtropics in the Northern Hemisphere and Southern Hemisphere. Therefore, we argue that the threshold value of Ri could be approximated as 1 rather than 1/4 when using ERA5-based Ri as a proxy for KHI. The occurrence frequency of subcritical Ri revealed by both datasets exhibits significant seasonal cycles over all climate zones. In addition, it is positively correlated with the standard derivation of orography at low levels and is exceptionally strong over the Niño-3 region at heights of 6–13 km. Furthermore, a high occurrence of subcritical Ri would likely be accompanied by strong wind speeds and intensive orographic or non-orographic gravity waves.

Mass Transfer Theory Based Analysis of Influencing Factors on Component Gradient of Near-surface Atmosphere on Venus

The atmosphere of Venus differs completely from that of Earth despite the planets’ similarity in size and mass. At Venus's surface, the atmosphere is hot and dense, with a temperature of approximately 735 K and a pressure of approximately 92 bar. The temperature profile from the Soviet VeGa-2 probe shows high instability of the near-ground potential temperature, which, according to relevant research, can be explained by the vertical gradient of N2 mole fraction. Based on the Maxwell–Stefan mass transfer theory, we propose a theoretical model of binary gas component for a quantitative discussion of influencing factors for the N2 vertical concentration gradient, which consist of temperature, gravity, specific heat ratio, mass relative factor, thermal diffusion factor, and CO2 flux. Our model shows that the 0%–3.5% N2 concentration gradient cannot be generated without CO2 flux in the near-ground atmosphere of Venus. And the result with CO2 source indicates that the 0.000001%–3.5% N2 concentration gradient at 0–7 km atmosphere can be generated by the 2.7 × 10−6 mol m−2 s−6 CO2 flux on Venusian surface, which is in agreement of gradient reckoned by VeGa-2's data. This magnitude of CO2 flux is close to the one produced by volcanic eruptions on Earth, indicating possible existence of volcanic activities on the surface of Venus. This work has provided the community a new vision to understand the influencing factors of Venusian atmospheres composition distribution.

Phase-modulated Rice model for statistical distributions of complex signals.

The basic Rice model is commonly used to describe complex signal statistics from randomly scattered waves. It correctly describes weak (Born) scattering, as well as fully saturated scattering, and smoothly interpolates between these extremes. However, the basic Rice model is unsuitable for situations involving scattering by random inhomogeneities spanning a broad range of spatial scales, as commonly occurs for sound scattering by turbulence in the atmospheric boundary layer and other scenarios. In such scenarios, the phase variations are often considerably stronger than those predicted by the basic Rice model. Therefore, the basic Rice model is extended to include a random modulation in the signal phase, which is attributable to the influence of the largest, most energetic inhomogeneities in the propagation medium. Various joint and marginal distributions for the complex signal statistics are derived to incorporate the phase-modulation effect. Approximations of the phase-modulated Rice model involving the Nakagami distribution for amplitude, and the wrapped normal and von Mises distributions for phase, are also developed and analyzed. The phase-modulated Rice model and various approximations are shown to greatly improve agreement with simulated data for sound propagation in the near-ground atmosphere.

Actinides Th and U in Atmospheric Particulate Matter in Yakutsk

The distribution of Th and U was studied in the near-ground atmosphere of the city of Yakutsk. The chemical compositions of particulate matter (PM) in the summer atmosphere and in the solid and soluble phases of the snowpack were studied in 2019–2020. In the summer atmosphere, Th and U are concentrated mostly in the dust fraction of PM, together with a group of siderophile elements. The wintertime PM is characterized by a more homogeneous size of its particles. PM minerals with which concentrations of actinides correlate are amphiboles and pyroxene for Th and carbonates for U. The Th and U concentrations were found out to systematically decrease in the sequence soil–summer PM (dust)–winter PM (snow), at the dominance of Th, but the aqueous phase of the snow contains U concentrations one order of magnitude higher than those of Th. The bulk (close to 90%) of actinides is deposited during the warm season. The total amount of actinides falling out in Yakutsk is 63 mg/(m2 year), with two-thirds of this amount being Th. This value may locally increase to 200 mg/(m2 year) and more in areas of contrasting anomalies, with the predominance of Th. The main sources of actinides entering the near-ground atmosphere of Yakutsk are dusting from the soil surface and emissions from vehicles, with lesser amounts coming from energy-producing and construction-industry facilities.

Signal power distributions for simulated outdoor sound propagation in varying refractive conditions.

Probability distributions of acoustic signals propagating through the near-ground atmosphere are simulated by the parabolic equation method. The simulations involve propagation at four angles relative to the mean wind, with frequencies of 100, 200, 400, and 800 Hz. The environmental representation includes realistic atmospheric refractive profiles, turbulence, and ground interactions; cases are considered with and without parametric uncertainties in the wind velocity and surface heat flux. The simulated signals are found to span a broad range of scintillation indices, from near zero to exceeding ten. In the absence of uncertainties, the signal power (or intensity) is fit well by a two-parameter gamma distribution, regardless of the frequency and refractive conditions. When the uncertainties are included, three-parameter distributions, namely, the compound gamma or generalized gamma, are needed for a good fit to the simulation data. The compound gamma distribution appears preferable because its parameters have a straight forward interpretation related to the saturation and modulation of the signal by uncertainties.

Anomalous vertical sound propagation and the ground-blocking of turbulence

Scattering by turbulence leads to random scintillations and coherence loss of sound waves, among other impacts. In a recent experiment involving transmissions from a 130-m tower to microphones on the ground [Kamrath et al., J. Acoust. Soc. Am. 149(3), 2055–2071 (2021)], the turbulence impacts on phase variances were shown to be considerably smaller for vertical and slanted paths than theoretically predicted. The primary cause is likely ground blocking of the turbulence: since the sound waves are impacted most strongly by the turbulent velocity fluctuations in the direction of propagation, and the ground blocks large vertical motions, the turbulence impacts are relatively weakened for vertical paths. An approach is described for including the ground blocking in the turbulence spectrum and, thus, in acoustic scattering calculations. The anisotropic propagation effect could possibly be used to measure the relative strengths of vertical and horizonal velocity fluctuations in the near-ground atmosphere.

Observation of the low-altitude cloud characteristics with Mie scattering Lidar at the Great Wall Station, Antarctica

The observation of polar clouds is of great significance to studying climate change in Antarctica. The modified Klett–Fernald method and Mie scattering light detection and ranging (Lidar) were used to study the characteristics of low-altitude clouds from February 15 to March 2, 2017 at the Great Wall Station. The temporal and spatial variations in the cloud extinction coefficient were obtained, and the optical and physical characteristics of the low-altitude clouds were statistically analyzed. The analysis shows that the near-ground atmosphere is very clean and the atmosphere at low heights is covered by low-altitude clouds. The meteorological and Lidar data show that the polar cyclone may be the main driving force of the cloud-height changes at this station.

Geochemical differentiation of atmospheric aerosols in natural zones of European Russia

Climate and environmental changes on Earth have become modern challenges to humanity. The main factor affecting the landscapes of Russia is an increase in air temperature and a decrease in precipitation. Because of these processes, the amount of aerosols in the near-ground atmosphere of the landscapes of the ETR (European territory of Russia) increases. The aim of the study is to determine the atmogeophysical and atmogeochemical indicators that reveal the interaction of the atmosphere and the diversity of natural landscapes in European Russia. Landscape-geochemical research methods make it possible to study geosystems with the participation of all landscape components and actual migration processes, especially the atmospheric migration of chemical elements. To determine the modern atmogeochemical existence, field comprehensive studies of the potential emission of matter in all natural zones of the ETR were carried out submeridionally - in the landscapes of the steppe, forest-steppe, forest and tundra zones of the ETR. The research results show that in the submeridional profile, the mass concentration of aerosols decreases regularly from south to north, the minimum concentrations of atmospheric aerosols are observed in the forest zone, in the tundra there was a slight increase due to anthropogenic landscapes and the influence of the sea. Analysis of the chemical composition of aerosols revealed that, among the elements of global importance, aluminosilicates naturally increase to the south of the ETR as elements of clay minerals that are widespread in the Russian Plain. The maximum phosphorus content occurs in the residential area with agricultural landscapes. Sulfur concentrations are confined to the semiarid zone of the ETR, then decrease in the forest zone and increase again in the technogenic regions and the tundra belt of the Kola Peninsula, surrounded by the sea. The concentrations of chemical elements of regional and local distribution in atmospheric aerosols are more differentiated on the ETR and depend on the natural and technogenic features of each region. Thus, heavy metals are more common in the Plain territories of the forest-steppe and forest zones of the ETR and are confined to the bedrock and technogenic sources. High concentrations of calcium and strontium are associated with areas of weathering of carbonate rocks. In general, increased concentrations of atmospheric aerosols with an increased content of anthropogenic elements are observed during the western and southern transport of air masses. At the same time, the amount of rainstorm precipitation increases when these aerosols act as condensation nuclei. To assess the current state of the atmosphere at the ETR, it is necessary to continue field measurements and organize European annual and seasonal geochemical monitoring at stationary observation points.

Vertical and slanted sound propagation in the near-ground atmosphere: Coherence and distributions.

Atmospheric turbulence causes acoustic signals to fluctuate and diminishes their coherence. These phenomena are important in applications such as source localization and sonic boom propagation. This article provides formulations for the spatial, cross-frequency, and temporal coherences of narrowband acoustic signals propagating over vertical and slanted paths in the atmosphere. Formulations for single- and two-point distributions of acoustic signals are also overviewed. The theoretical formulations are compared with data from a comprehensive sound propagation experiment carried out in 2018 at the National Wind Technology Center (Boulder, CO). The theories for sound propagation in a turbulent atmosphere, when combined with turbulence models incorporating shear and buoyancy instabilities, correctly predict the measured spatial coherence, which is primarily affected by small-scale isotropic turbulence. For relatively small coherence times, this approach also correctly predicts the temporal coherence. However, the approach underpredicts the cross-frequency coherence and temporal coherence for relatively large coherence times, which are affected by large-scale anisotropic buoyancy-driven velocity fluctuations. For different regimes ranging from unsaturated to fully saturated scattering, the measured distributions agree well with the theoretical predictions.

Vertical and slanted sound propagation in the near-ground atmosphere: Amplitude and phase fluctuations.

Sound propagation along vertical and slanted paths through the near-ground atmosphere impacts detection and localization of low-altitude sound sources, such as small unmanned aerial vehicles, from ground-based microphone arrays. This article experimentally investigates the amplitude and phase fluctuations of acoustic signals propagating along such paths. The experiment involved nine microphones on three horizontal booms mounted at different heights to a 135-m meteorological tower at the National Wind Technology Center (Boulder, CO). A ground-based loudspeaker was placed at the base of the tower for vertical propagation or 56 m from the base of the tower for slanted propagation. Phasor scatterplots qualitatively characterize the amplitude and phase fluctuations of the received signals during different meteorological regimes. The measurements are also compared to a theory describing the log-amplitude and phase variances based on the spectrum of shear and buoyancy driven turbulence near the ground. Generally, the theory correctly predicts the measured log-amplitude variances, which are affected primarily by small-scale, isotropic turbulent eddies. However, the theory overpredicts the measured phase variances, which are affected primarily by large-scale, anisotropic, buoyantly driven eddies. Ground blocking of these large eddies likely explains the overprediction.

MEMS-based electric field sensor with environmental adaptability consideration and its application in the near-ground atmosphere

The near-ground electric field (E-field) is an important parameter needed to be measured for lightning warning systems. Yet, most of the E-field sensors are based on bulky and expensive rotate-vane mills. This paper presents a novel MEMS(Micro-electro-mechanical Systems)-based sensor and its application in near-ground atmospheric E-field long-term monitoring. We solve the problem of environmental adaptability by means of a novel macromolecular polymer package and moisture-proof design. To enhance the electric field resolution, a Φ 36mm×17mm probe is mounted separately from the signal processing circuit. Both finite element simulation and experimental results prove that this sensor could detect the electric field as small as 5V/m. The real-time monitoring data have a good consistency with those of the commercial electric field mill.

Модель воздействия гравитационно-волнового излучения релятивистских двойных звездных систем на электрическое поле в тропосфере

A model is proposed which explains the observed effect of gravity-wave influence of relativistic binaries to the Earth’s electric field vertical projection in the near-ground atmosphere layer. The considered mechanism is a perturbation of the Earth’s orbit by the gravity waves which leads to a small displacement between the Earth and the Earth’s atmosphere free electric charge. The proposed model give amplitude estimations of Ez components spectrally localized at the relativistic binaries gravity waves’ frequencies which do not contradict to the observations.

A Review on Electrodynamic Influence of Atmospheric Processes to the Ionosphere

This work is an attempt to critically analyze the existing theoretical models of the impact of earthquake preparation processes on the state of the earth’s atmosphere and ionosphere in the zone of growing seismic activity, as well as the mechanisms of formation and transfer of disturbances in various media over the earthquake center. The determining factor (criterion) of the analysis is the degree of compliance of the simulation results with experimental data obtained at various phases of earthquake development by direct and remote diagnostic methods using ground and aerospace technologies. The key role is played by the model’s compliance with the results of measuring electric fields and currents in the near-ground atmosphere and ionosphere, small-scale ionospheric inhomogeneities and correlated field-aligned currents and electromagnetic ULF/ELF emissions. A full-fledged model should also explain the origin of such seismic related phenomena as the generation in the troposphere and over-horizon propagation of pulsed VHF radiation, thermal effects and associated IR emissions as well as the modification of plasma distribution in the D, E and F layers of the ionosphere. The use of this criterion in the analysis allowed us to identify a theoretical model that most fully describes the totality of the above-mentioned experimental data within a single physical mechanism. This is an electrodynamic model based on the perturbation of the conductivity current in the global atmosphere—ionosphere electric circuit due to the injection of charged aerosols into the atmosphere during the preparation and development of an earthquake. The present paper describes this model and the formation mechanisms of related phenomena in the atmosphere and ionosphere, which can be considered as short-term precursors to earthquakes.

Influence of Atmosphere Near-Surface Layer Properties on Development of Cloud Convection

A two-dimensional mathematical model of moist air convection in the sub-cloud and cloud layers is proposed. A theoretical analysis of the influence of near ground atmospheric parameters on the development of sub-cloud and cloud convection is provided, and the criteria of convection development are considered. As a rule, this relationship is parameterized in general circulation, regional or mesoscale models of the atmosphere. Therefore, achieving a more complete and correct understanding of this relationship can lead to an improvement in the accuracy of weather forecasts. The mathematical model describes the system of the equations of motion, heat conductivity and the continuity equations for a two-dimensional vertical plane. The approximate analytical solution of the system of equations is obtained. Expressions for the estimation of the convection height and height of maximum velocity are derived for vertical and horizontal components of updraft wind and for vertical distribution of temperature. From the expressions obtained, the criterion of sub-cloud convection development is derived. The expressions for the convection parameters at a condensation level have also been formulated, from which the criterion of cloud development through convection is derived. It is established that the development of cloud convection depends on absolute values of the dew point deficit in a near-surface layer and, in a greater degree, on vertical gradients of water vapor mass fraction. It is shown that at certain critical values of a vertical gradient of water vapor mass fraction “explosive convective growth” is observed. The application of the obtained results to artificial stimulation of convection by means of air heating in the near-ground atmosphere has shown that the success of such an application and the required air heating-up depend on: (i) the vertical temperature gradient; (ii) the vertical dew-point gradient; and (iii) the value of the dew point deficit in the near-ground layer. The analysis performed has shown the possibility of successful stimulation of artificial convection under specific favorable atmospheric conditions.

Winter thunderstorms in Kamchatka

Winter thunderstorms in Kamchatka are rare meteorological phenomena. To investigate the nature of this phenomenon, time variations of quasistatic electric field and meteorological quantities at «Paratunka» observatory, IKIR FEB RAS (φ = 52:97° N; λ = 158:25° E), and the data on solar, seismic and cyclonic activities available in INTERNET were used as a thunderstorm activity indicator. It was shown that powerful solar flares accompanied by radiation increases in visible and infra-red spectra as well as the Earth infra-red radiation entering the atmosphere before powerful earthquakes with magnitude M > 8 may be additional sources of heat in the near-ground atmosphere of Kamchatka. The impact of tropical cyclones on the processes of thunderstorm activity formation in Kamchatka during weak seismic activity has been determined insufficiently and requires further detailed investigation.

Measuring anisotropy ellipse of atmospheric turbulence by intensity correlations of laser light.

An experimental study has been performed of a laser beam propagating horizontally through the near-ground atmosphere above a grassy field at the University of Miami (UM) Coral Gables campus. The average intensity, scintillation index, and intensity correlation function are measured in the receiver plane for three channels with different turbulent conditions and at three different heights above the ground. Our results reveal that along short links (210m) only the intensity correlation function captures the anisotropic information of turbulence, corresponding to the refractive index anisotropy ellipse of atmospheric fluctuations. In addition, we report an interesting phenomenon relating to turbulence eddy orientation near the ground. We confirmed that the experimental results are in agreement with the numerical simulations based on the multiple phase-screen method. Our findings provide an efficient method of determining the anisotropic parameters of atmospheric turbulence.

Diurnal Variations of Air-Soil Exchange of Semivolatile Organic Compounds (PAHs, PCBs, OCPs, and PBDEs) in a Central European Receptor Area.

Concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) in air and soil, their fugacities, and the experimental soil-air partitioning coefficient (KSA) were determined at two background sites in the Gt. Hungarian Plain in August 2013. The concentrations of the semivolatile organic compounds (SOCs) in the soil were not correlated with the organic carbon content but with two indirect parameters of mineralization and aromaticity, suggesting that soil organic matter quality is an important parameter affecting the sorption of SOCs onto soils. Predictions based on the assumption that absorption is the dominant process were in good agreement with the measurements for PAHs, OCPs, and the low chlorinated PCBs. In general, soils were found to be a source of PAHs, high chlorinated PCBs, the majority of OCPs and PBDEs, and a sink for the low chlorinated PCBs and γ-hexachlorocyclohexane. Diurnal variations in the direction of the soil-air exchange were found for two compounds (i.e., pentachlorobenzene and p,p'-dichlorodiphenyldichloroethane), with volatilization during the day and deposition in the night. The concentrations of most SOCs in the near-ground atmosphere were dominated by revolatilization from the soil.

Complex Aerosol Experiment in Western Siberia (April – October 2013)

The primary project objective was to accomplish the Complex Aerosol Experiment, during which the aerosol properties should be measured in the near-ground layer and free atmosphere. Three measurement cycles were performed during the project implementation: in spring period (April), when the maximum of aerosol generation is observed; in summer (July), when atmospheric boundary layer height and mixing layer height are maximal; and in late summer – early autumn (October), when the secondary particle nucleation period is recorded. Numerical calculations were compared with measurements of fluxes of downward solar radiation. It was shown that the relative differences between model and experimental values of fluxes of direct and total radiation, on the average, do not exceed 1% and 3% respectively.

ЭФФЕКТЫ СОЛНЕЧНОГО ЗАТМЕНИЯ 20 МАРТА 2015 Г. В ИОНОСФЕРЕ НАД ЕВРОПОЙ: РЕЗУЛЬТАТЫ ИОНОЗОНДОВЫХ НАБЛЮДЕНИЙ

ЭФФЕКТЫ СОЛНЕЧНОГО ЗАТМЕНИЯ 20 МАРТА 2015 Г. В ИОНОСФЕРЕ НАД ЕВРОПОЙ: РЕЗУЛЬТАТЫ ИОНОЗОНДОВЫХ НАБЛЮДЕНИЙ

Reaction of electric and meteorological states of the near-ground atmosphere during a geomagnetic storm on 5 April 2010

The effects of a geomagnetic storm on 5 April 2010 on electric parameters of the atmospheric near-ground layer in Kamchatka have been investigated. Three processes over the course of the storm were identified. Air electroconductivity began to decrease 4 h before the storm, and this lasted for 20 h. The storm's sudden commencement caused potential gradient oscillations with amplitudes up to 300 V/m. During the stages of the storm, a significant increase in the atmosphere ion content unipolarity coefficient occurred.