Presence Of Temperature Inversion Research Articles

Scenario Analysis of the Risk of Gas Pipeline Failures in the North

Low temperatures and abnormal meteoconditions of the North have significant effect both on the accident frequency, and on accident development. Abnormal weather conditions of the North are characterized by the powerful temperature inversions arising at an anti-cyclone due to the emission of permafrost soil at extremely low temperatures of air and conditions of air stagnation. These abnormal conditions influence process of gas dispersion in the atmosphere, promoting its deceleration and formation of explosive concentration of gas at the Earth’s surface. Based on the results of gas pipeline failures analysis occurred in the North, the main causes of gas pipeline accidents were identified, the gas leakage “fault tree” from the gas pipeline was developed with estimation of failures frequencies, and the frequency of emergency situations in case of gas leakage from the gas pipeline was estimated. The most dangerous scenarios of gas pipeline accident evolution have been identified and their risk levels in the zone of the damage factors have been assessed on the basis of acceptable risk criteria. It is justified to increase the action range of damage factors in an explosion of methane -air mixture cloud in open space at presence of temperature inversion.

The assessment of the atmospheric air quality in Tomsk with the use of a mesoscale photochemical model

The paper presents the results of studying the influence of the development of meteorological situation in clear weather with a weak wind on the level of atmospheric surface air pollution in the city of Tomsk (Russia). Mesoscale meteorological and photochemical models with a new kinetic scheme were applied to the analysis. The main local weather conditions were identified, in which numerical calculations show increased values of the air pollution index. The numerical predictions have confirmed an increase in the ground-level concentration of pollutants in the presence of temperature inversion or isothermy.

Pollution of the snow surface with polycyclic aromatic hydrocarbons during the formation of frost

When analyzing chemical compositions of snow the high variability of content of polycyclic aromatic hydrocarbons (PAHs) in snow cover between snowfalls is observed. Researchers explain this by concentrating of snow. However, another mechanism of atmospheric contamination of the snow cover surface is possible. It may be a precipitation of fine crystals of PAHs from the atmosphere in the composition of cryohydrates, which can form aerogenic anomalies on the snow surface at formation of hoarfrost. The process starts in the atmosphere during the interaction of finely dispersed crystals of PAHs with cloud supercooled drops. This results in the cryogenic concentration of solid particles of PAHs by way of formation of solid eutectic mixture – cryohydrates, which are a two-phase system consisting of a fine mixture of crystals of solid particles and ice. Evidence of their manifestation is the presence of the Forel hatching on the surface of the facets of the hoarfrost crystals appearing due to the different optical density of alternating zones, which consist of interpenetrating domains of crystallized solid aerosols and ice. At the same time, due to the presence of temperature inversion over the snow cover and its drying effect on the near-snow layer of air, a stable mass transport of water vapor down to the snow cover is formed, which can initiate the flow of fine cryohydrates from the PAHs. Therefore, the growth of atmospheric ice crystals, begun in the surface atmosphere, continues on the snow surface during formation of hoarfrost, thus creating a special nano-relief of snow cover. The paper presents the results of observations of changes in the concentration of individual PAHs in the upper 18 mm layer of snow at accumulation of the surface hoarfrost during a long period between snowfalls. Some micro-morphological features of the forms of skeletal rime micro-crystals are shown, with which an increase in the nano-roughness of the snow surface is associated, as well as the manifestation of the signal of the aerogenic PAH anomaly on the snow surface. Since the conditions for the formation of surface hoarfrost occur more often than for snowfalls, the hoarfrost may be an informative object of testing when detecting hydrocarbon contamination of snow cover during the intervals between snowfalls.

The Role of Emissivity in the Detection of Arctic Night Clouds

Detection of clouds over polar areas from satellite radiometric measurements in the visible and IR atmospheric window region is rather difficult because of the high albedo of snow, possible ice covered surfaces, very low humidity, and the usual presence of atmospheric temperature inversion. Cold and highly reflective polar surfaces provide little thermal and visible contrast between clouds and the background surface. Moreover, due to the presence of temperature inversion, clouds are not always identifiable as being colder than the background. In addition, low humidity often causes polar clouds to be optically thin. Finally, polar clouds are usually composed of a mixture of ice and water, which leads to an unclear spectral signature. Single and bi-spectral threshold methods are sometimes inappropriate due to a large variability of surface emissivity and cloud conditions. The objective of this study is to demonstrate the crucial role played by surface emissivity in the detection of polar winter clouds and the potential improvement offered by infrared hyperspectral observations, such as from the Infrared Atmospheric Sounding Interferometer (IASI). In this paper a new approach for cloud detection is proposed and validated exploiting active measurements from satellite sensors, i.e., the CloudSat cloud profiling radar (CPR) and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). For a homogenous IASI field of view (FOVs), the proposed cloud detection scheme tallies with the combined CPR and CALIOP product in classifying 98.11% of the FOVs as cloudy and also classifies 97.54% of the FOVs as clear. The Hansen Kuipers discriminant reaches 0.95.

Mixing in the surface layers in association with internal waves during winter in the northwestern Bay of Bengal

The upper ocean has complex and variable temperature stratification, and the surface layers in the northwest Bay of Bengal in winter indicate the presence of transient thermal inversions that wane with the advancement of the season. During winter, the sea surface loses heat and the surface waters of the coastal regions of the east coast of India are fairly stratified with the residual freshwater atop from the preceding southwest monsoonal discharge. The vertical stability favors the formation and sustenance of temperature inversions. To investigate the mechanism and the influence of ubiquitous internal waves that thrive on stability, a three-dimensional Princeton Ocean Model is configured for the east coast of India and is applied to study the process in the surface layers in association with the internal waves. The model domain constitutes a variable curvilinear grid, and the input fields comprise bathymetry, initial temperature and salinity, wind stress, air-sea heat fluxes and tidal forcing at the open boundaries. The numerical experiments demonstrate that vertical stability alone cannot cause, support or augment the internal wave oscillations, if the stratification is attributed to salinity only. Internal waves may therefore be perceived in stable layers, essentially from temperature-induced stratification. Despite stratification and enough vertical density gradient in the upper ocean, the conditions may not suit for the occurrence of internal waves due to thermal diffusive processes that overpower the salinity gradients. The vertical spreading of heat due to double diffusion is believed to be transparent to tidal forcing as the generation of internal waves is subdued even under density stratification. The model simulations indicate that the horizontal convergence/divergence motions, required for the manifestation of internal waves at the surface are inhibited in the presence of temperature inversion. The available SAR imageries in winter endorse the model simulations to this effect.

Carbon oxide in the surface air (Obninsk monitoring station)

The results of measurements of the concentration of carbon oxide (CO) in the atmospheric surface layer over the town of Obninsk (in European Russia, 105 km to the southwest of Moscow) are presented. Air samples were analyzed with the aid of a measuring system consisting of a Fourier-spectrometer and an optic multipass cell. The CO concentration was measured simultaneously with the measurements of air temperature up to a height of 300 m. The measurement data obtained from February 1998 to January 2009 suggest the presence of variations within the range 100–450 ppb (∼80% of all the data) and nonperiodic relatively short-term and anomalously high CO concentrations that reach several ppm. The highest concentrations are due to CO accumulated in the surface air in the presence of temperature inversion and during forest fires. The measurements of the concentration of CO throughout a day revealed its morning and evening maxima, which coincide in time with the increased traffic current. The maxima and minima of seasonal variations in the monthly mean concentrations of CO, which are due to variations in the sources and sinks of CO that happen within a year, are observed in January and June, respectively. The amplitudes of seasonal variations amounted to (53 ± 10)% of the annual mean. The annual mean concentration of CO decreased by ∼12% over the measurement period. A comparison was made with observational data obtained at five monitoring stations located in the latitudes that are close to the latitude of Obninsk. Over the European continent, the concentration of CO tends to decrease with a longitude decrease as it goes from east to west.

Coordinated MST radar and lidar observations for the study of mesospheric structures over a tropical station

VHF radar observations at a frequency of 53 MHz at Gadanki (13.5°N,79.2°E), India, during the period from September 1995 to August 1999 are used to study the tropical mesospheric structures. MST radar echoes have shown an enhancement in echo power of about 6– 8 dB above the average noise level. These echoes are intermittent in time and can be observed at an altitude between 70 and 76 km . The seasonal variation of these echoes shows the maximum percentage occurrence during summer, closely followed by equinoxes and minimum during winter. This seasonal variation is also accompanied by shifting of height to lower heights during winter. Coordinated MST radar and Nd:YAG lidar observations were conducted to study the mesospheric structures during March 1998–June 1999. In the Lidar temperature profiles, inversion of about 20– 30 K is observed at the heights of the MST radar-enhanced echoes. Enhanced radar reflectivity is observed on both the preceding and succeeding days of lidar observations of strong temperature inversion. Percentage occurrence of MST radar echoes and temperature inversions show one-to-one correspondence for most of the cases. The effect of temperature inversion on the radar reflectivity is also studied. The presence of temperature inversion and enhanced radar reflectivity are discussed in the light of gravity-wave breaking processes at that height region.