Vertical Temperature Distribution Research Articles

Parameterization of Solar Radiation Absorption by Snow–ice Cover in the Thermodynamic Sea Ice Model of the Sea of Azov

Purpose. The work is aimed at assessing the influence of choice of the parameterization scheme of the snow and ice radiation features upon reproduction of seasonal evolution of the snow–ice cover thickness and temperature distribution in it in the Taganrog Bay top part. Methods and Results. Thermal seasonal dynamics of the snow–ice cover thickness in the northeastern part of the Taganrog Bay was studied using a non-stationary thermodynamic model of sea ice. The model reproduces formation of ice and accumulation of snow on its surface, spatial-temporal change in their thermophysical characteristics, melting of the snow–ice cover, vertical distribution of temperature, and solar radiation absorbed in its thickness at a preset timed data on the meteorological parameters. In the numerical solution of the heat conductivity equation for snow and ice including a radiation source, a computational grid permitting to maintain spatial resolution of the temperature profiles in the snow–ice cover during its melting and growth was applied. Two variants of parameterization of solar radiation transfer in the sea ice were considered. The first version assumed exponential decay of radiation with the constant transmittance and extinction coefficients. In the second one, a two-layer scheme of the solar radiation penetration into ice was used; it simulated the near-surface transition layer. Attenuation of intensity of solar radiation in the snow thickness was described by the Bouguer–Lambert law with the extinction coefficient both as independent of the snow thermophysical characteristics and as represented by the function of its density. The numerical experiments with the purpose to reproduce seasonal evolution of the snow–ice cover thickness and its vertical temperature profile in the Taganrog Bay top part were performed for the winter season, 2016/17. Comparative analysis of the simulation results and the sea ice thickness values taken from the ESIMO ice maps made it possible to choose a combination of the model parameters that provides the best correspondence between the calculated and actual values. Conclusions. It is shown that in reproducing the seasonal changes in the ice cover thickness in the Taganrog Bay top part in winter, 2016/17, the choice of the transmittance and extinction coefficients for white ice represented by the cloudiness functions, on the one hand, and the thickness of the layer with the most intense absorption of short-wave radiation ~ 4 cm, on the other, turned out to be the most justified.

Thermal Tides in the Upper Cloud Layer of Venus as Deduced From the Emission Angle Dependence of the Brightness Temperature by Akatsuki/LIR

AbstractThe brightness temperature of the Venus disk obtained by Longwave Infrared Camera (LIR) on board Akatsuki shows clear limb darkening at low and middle latitudes. The profile of limb brightness reflects the vertical distributions of atmospheric temperature and the optical thickness of the cloud particles. Horizontal distributions of brightness temperature obtained by LIR during ∼5.8 Venusian years were analyzed to investigate the vertical structure of the brightness temperature distribution above the cloud tops based on the emission angle dependence of the sensing altitude. Emission angles were converted to sensing altitudes by a radiative transfer calculation with nominal temperature and cloud particle distributions based on past observations. We show a local time‐altitude cross section of the brightness temperature deviation above the cloud tops for three latitudinal zones. The derived vertical amplitude distribution of the diurnal and semidiurnal tides above ∼68 km is mostly explained by the classical theory of thermal tides. A semidiurnal tide in which the phase shifts upstream with altitude is clearly seen in the equatorial region. By applying the dispersion relation of the internal gravity wave to the observed wave structure, it was found that the zonally averaged zonal wind velocity at altitudes of 66–71 km was approximately the same as the known superrotation velocity. By comparing the observed and simulated vertical phase structures, it is suggested that the tidal wave structure seen in the equatorial cloud tops is an aspect of upward propagation of a gravity wave generated in the upper cloud layer by solar heating.

Parametrizatsiya pogloshcheniya solnechnoy radiatsii snezhno-ledyanym pokrovom v termodinamicheskoy modeli l'da Azovskogo morya

Purpose. The work is aimed at assessing the influence of choice of the parameterization scheme of the snow and ice radiation features upon reproduction of seasonal evolution of the snow-ice cover thickness and temperature distribution in it in the Taganrog Bay top part. Methods and Results. Thermal seasonal dynamics of the snow-ice cover thickness in the northeastern part of the Taganrog Bay was studied using a non-stationary thermodynamic model of sea ice. The model reproduces formation of ice and accumulation of snow on its surface, spatial-temporal change in their thermophysical characteristics, melting of the snow-ice cover, vertical distribution of temperature, and solar radiation absorbed in its thickness at a preset timed data on the meteorological parameters. In the numerical solution of the heat conductivity equation for snow and ice including a radiation source, a computational grid permitting to maintain spatial resolution of the temperature profiles in the snowice cover during its melting and growth was applied. Two variants of parameterization of solar radiation transfer in the sea ice were considered. The first version assumed exponential decay of radiation with the constant transmittance and attenuation coefficients. In the second one, a two-layer scheme of the solar radiation penetration into ice was used; it simulated the near-surface transition layer. Attenuation of intensity of solar radiation in the snow thickness was described by the Bouguer – Lambert law with the attenuation coefficient both as independent of the snow thermophysical characteristics and as represented by the function of its density. The numerical experiments with the purpose to reproduce seasonal evolution of the snow-ice cover thickness and its vertical temperature profile in the Taganrog Bay top part were performed for the winter season, 2016/17. Comparative analysis of the simulation results and the sea ice thickness values taken from the ESIMO ice maps made it possible to choose a combination of the model parameters that provides the best correspondence between the calculated and actual values. Conclusions. It is shown that in reproducing the seasonal changes in the ice cover thickness in the Taganrog Bay top part in winter, 2016/17, the choice of the transmittance and attenuation coefficients for white ice represented by the cloudiness functions, on the one hand, and the thickness of the layer with the most intense absorption of short-wave radiation ∼ 4 cm, on the other, turned out to be the most justified.

A new assessment of the circulation of Atlantic and Intermediate Waters in the Eastern Mediterranean

A simulation of the Mediterranean circulation between 2011 and 2020 at a resolution of 3–4 km in the Eastern basin was compared to vertical profiles and horizontal distributions of temperature and salinity from Argo profilers distributed throughout the basin. The comparison is marked by high temporal (∼0.9) and spatial (0.6–0.8) correlations and low biases. Comparisons of SST with satellite imagery have also shown strong similarities for numerous structures over a wide range of spatial scales. The simulation is used to describe the mean circulation of surface Atlantic Waters and Intermediate Waters in winter and summer.The surface circulation is cyclonic alongslope, stronger and more stable in winter. In summer, the current veins are sometimes interrupted and replaced by trains of eddies like in the South Ionian. In other cases, the current becomes very narrow and stuck to the coast as along the Ionian east coast or the Middle East coast. In winter, surface and Levantine Intermediate Waters exit from the Levantine mainly through the Aegean, while in summer, they exit westward south of Crete. The Aegean tends in summer to be isolated by eddies that develop on both sides of the Cretan Arc. The juxtaposition of Ierapetra, the Rhodes Gyre and the Mersa-Matruh Eddies produces a southward path across the Levantine basin at about 27 − 28°E which delimits a large cyclonic circulation to the east which tends to separate the two parts of the basin (west and east Levantine). Concerning the Levantine Intermediate Waters, the alongslope cyclonic circulation all around the Levantine basin in winter is no longer maintained in summer as a large anticyclonic circulation occupies the southeast of the basin. The intermediate waters entering the Ionian either through southern Crete in summer or through the Aegean in winter, are submitted to a strong northward, southward and even westward dispersion by Pelops and the nearby anticyclonic areas. The presence of recurrent anticyclones between 35 and 37°N along a band extending from west to east of the Ionian also produces a vertical dispersion of intermediate water. Finally, the circulation of intermediate water in the South Ionian is marked by an important seasonality with the presence in summer of a large anticyclonic circulation that seems to be wind induced and finally drives a secondary branch to the Sicily Channel. A climatology for the transport through the different straits is discussed and simplified representations of the circulation are proposed.

Performance of the wall implanted with heat pipes on indoor thermal environment

In order to improve the utilization of solar energy absorbed by the building wall, a passive building technology, that is the wall implanted with heat pipes, had been proposed. In the present study, two rooms with the same environmental conditions were built, and the one with a wall implanted with heat pipes installed was taken as a test room and the other as a control. The dynamic heat transfer characteristics of a wall implanted with heat pipes in transition season and its impact on indoor thermal environment were studied experimentally. The results showed that the application of a wall implanted with heat pipes could increase the indoor temperature by about 0.5 °C and would assert a positive influence on the vertical distribution of temperature. The PMV-PPD values of two rooms were calculated to compare and evaluate the improvement in thermal comfort, and the results indicated that the wall implanted with heat pipes reduced the dissatisfaction rate by more than one seventh in comparison to the indoor thermal environment. Also, it enhanced the PMV value. Therefore, wall implanted with heat pipes as an auxiliary heat source has a good effect on the indoor thermal environment during the transition season.

Experimental study on local floor heating mats to improve thermal comfort of workers in cold environments

This study investigates the effect of local floor heating mats on the thermal comfort of workers in cold environments. Experiments were performed with two sizes of floor heating mats under two power input levels. Twenty subjects participated in the experiments at three air temperature conditions of 11, 13, and 15 °C. The participants performed three activities in the experiments: sitting, sitting + packing, and standing + packing. Subjective questionnaires were collected, including the overall thermal sensation vote (TSV), local thermal sensation of feet (TSVfeet), and thermal comfort vote (TCV). The subjects’ mean skin temperature (MST) and cochlear temperature were measured. The results show that subjects' TSV, TSVfeet, and TCV significantly improved when using heating mats of larger size and higher power input. TSVfeet increased faster than TSV. When the air temperature decreases, TSVfeet should be higher to keep TSV close to neutral. Moreover, subjects' MST and cochlear temperature also increased slightly when heating mats were adopted. Both MST and cochlear temperature were positively correlated with TSV. Heating mats also increased the subjects' working efficiency, related to the TSV and TCV. Analysis of the vertical temperature distribution in the vicinity of the subjects showed that with heating mats, the thermal plume was enhanced, and the ambient air temperature increased slightly. Hence, local floor heating mats can effectively improve the thermal comfort and working efficiency of workers in cold environments.

Irreversibilities in natural convection inside a right-angled trapezoidal cavity with sinusoidal wall temperature

Analysis on natural convective heat transfer in different engineering systems allows optimization of the technical apparatus. For this purpose, numerical simulation of the fluid flow and heat transport within the system is combined with study of entropy generation. The latter is very important considering the Gouy–Stodola theorem of thermodynamics. The present research deals with the mathematical modeling of thermal convection and entropy generation in a right-angled trapezoidal cavity under the influence of sinusoidal vertical wall temperature distribution. Control Oberbeck–Galerkin finite element technique has solved Boussinesq equations formulated using the non-dimensional primitive variables. Analyses of flow structures, thermal and entropy generation patterns for different values of the Rayleigh number, and parameters of non-uniform wall temperature were performed. It was found that a rise in the sinusoidal wall temperature amplitude increases the average Nusselt and Bejan numbers and average entropy generation. Moreover, growth in the non-uniform wall temperature wave number decreases the energy transport strength and Bejan number.

Effect Analysis of the Digital Spectrometer FFT Algorithm on THz Atmospheric Limb Sounder (TALIS) System Sensitivity

THz Atmospheric Limb Sounder (TALIS) is a microwave radiometer designed by the National Space Science Center of the Chinese Academy of Sciences (NSSC, CAS) for measuring the vertical distribution of temperature and chemical constituents in the middle and upper atmosphere. The digital spectrometer is an important part of TALIS’ back end, which mainly realizes the function of spectral analysis. The radix 16 real-time complex fast Fourier transform (FFT) algorithm used in the digital spectrometer was obtained by improving and combining the parallel processing and complex processing of the FFT algorithm. In this study, the digital spectrometer parameter selection is systematically presented, and the effect of the digital spectrometer FFT algorithm on the TALIS system sensitivity is analyzed based on the TALIS system simulation model we established in the previous stage of this research. The results show that the actual full-band sensitivity obtained after using the FFT algorithm is consistent with the ideal full-band sensitivity of TALIS for different integration time, spectral resolutions, and quantization bits. However, the results of the comparison of the actual sub-band sensitivity after using the FFT algorithm with the ideal sub-band sensitivity show that the deterioration of the sub-band sensitivity will be caused by the FFT algorithm. The mean value of the deterioration ratio was found to be approximately 18%, and the maximum value of the deterioration ratio was approximately 33%.

Experimental study on the characteristics of temperature distribution of two pool fires with different transverse locations in a naturally ventilated tunnel

The interaction between multiple fires is complex, in which the theory of single fire is not applicable. This study focuses on the combustion characteristics and temperature distribution of two pool fires with different transverse locations in a model tunnel under natural ventilation. In this study, 84 groups of combustion experiments of two ethanol pool fires were designed by varying the spacing between two pool fires (denoted by S), transverse distance between the geometric center of pool fires and tunnel sidewall (L), and side length of oil pan (D). The experimental results show that when L = 50 cm and L = D/2, mass loss rate decreases along with a bigger S/D, and reaches the minimum for L = 50 cm and the maximum for L = D/2. However, mass loss rate first increases and then decreases with S/D for L = 30 cm and L = 20 cm, which is controlled by the competition between air entrainment and radiant heat feedback. In order to describe the influences of fire source spacing and transverse distance, a prediction model of maximum temperature rise under the tunnel ceiling is developed, which matches the experimental results well. Under the case of no flame merging, longitudinal temperature distribution is insensitive to the transverse location rather than the spacing between the fire sources. Moreover, it is found that the vertical temperature distribution far from the fire sources matches the Gaussian distribution well. The results of this work can provide a significant reference for the risk assessment of tunnel fires with two fire sources.

Characteristics of vertical atmosphere based on five-year microwave remote sensing data over Wuhan region

To enhance the understandings of the regional climatic characteristics, vertical distributions of temperature and relative humidity (RH), height of atmospheric boundary layer (ABLH), integrated water vapor (IWV), and liquid water path (LWP) were analyzed based on five-year observations from a ground-based microwave radiometer over Wuhan. Performance of ground-based microwave radiometer (MWR) was also estimated by comparing with the radiosonde (RS) data. The temperature profile measured by the microwave radiometer was better under cloudy conditions, while the RH profile had higher accuracy under cloud-free conditions. The IWV from MWR generally showed a good consistency with RS data (R2 > 0.95), whereas a slight underestimation was found under cloud-free conditions as the slope of linear regression was 0.898. Variations of temperature and humidity profiles showed a distinct seasonal cycle in this region. Two abrupt turning points happened around April and October respectively, resulting in cold winters and hot and wet summers. The highest and lowest values of temperature appeared at ~15 and ~ 6 local time respectively and the vertical extension of temperature fluctuated between 5 and 7 km depending on the season, mainly related to incoming solar irradiation intensity. Due to the inhomogeneity of temperature changes in vertical direction, the ABLH also showed distinct diurnal (0.79–1.98 km) and seasonal (1.12–2.01 km) variations. The IWV was a unimodal distribution in a year. The minimum and maximum were found in December (~10.3 kg/m2) and July (~54.7 kg/m2). An abnormal high RH (a positive anomaly of ~5.7% below 2 km) was observed in February, higher than January and March. Meanwhile, the highest average LWP (114.4 g/m2) was also observed in February. Low temperature and increasing IWV caused more water vapor to condense into water droplets and form clouds in the atmosphere, and thus the RH and LWP increased. The above findings provided estimations of microwave radiometer performance and enhanced our understandings of the regional climatic characteristics.

Investigation on vertical temperature profile of thermal ejected plume from a compartment fire with an adjacent side wall

This paper presents an investigation of vertical temperature profile of the thermal ejected plume from a compartment fire with an adjacent side wall, which has not been quantified in the literatures. A full-scale compartment model with a vertical facade and an adjacent side wall positioned at the side of the window has been set up in the numerical simulations. The vertical temperature distribution upon the facade with various window dimensions, total heat release rates and side wall separation distances is measured. By comparing with former study, the validity of the numerical simulation results has been confirmed, which shows good agreement with the previous experimental data. Result reveals that only when the side wall separation distance (D) is less than a critical value for each window dimension, will the vertical temperature profile of thermal ejected plume affect by the constraining boundary of adjacent side wall, otherwise it will remain basically the same. Then, a new correlation is proposed to describe the constraining effect of side wall on the vertical temperature profile by introducing a coefficient α. Numerical simulation results for various window dimensions, total heat release rates and side wall separation distances can be well collapsed by the newly proposed correlation.

A Thermal Effect Model for the Impact of Vertical Groundwater Migration on Temperature Distribution of Layered Rock Mass and Its Application

On the basis of the one-dimensional heat conduction–convection equation, a thermal effect model for vertical groundwater migration in the stratified rock mass was established, the equations for temperature distribution in layered strata were deduced, and the impacts of the vertical seepage velocity of groundwater and the thermal conductivity of surrounding rocks on the temperature field distribution in layered strata were analyzed. The proposed model was employed to identify the thermal convection and conduction regions at two temperature-measuring boreholes in coal mines, and the vertical migration velocity of groundwater was obtained through reverse calculation. The results show that the vertical temperature distribution of the layered rock mass is subject to the migration of the geothermal water; the temperature curve of the layered formation is convex when the geothermal water travels upward, but concave when the water moves downward. The temperature distribution in the stratified rock mass is also subject to the thermal conductivity of the rock mass; greater thermal conductivity of the rock mass leads to a larger temperature difference among regions of the rock mass, while weaker thermal conductivity results in a smaller temperature difference. A greater velocity of the vertical migration of geothermal water within the surrounding rock leads to a larger curvature of the temperature curve. The model was applied to a study case, which showed that the model could appropriately describe the variation pattern of the ground temperature in the stratified rock mass, and a comparison between the modeling result and the measured ground temperature distribution revealed a high goodness of fit of the model with the actual situation.

Towards an Understanding of the Structure of Jupiter’s Atmosphere using the Ammonia Distribution and the Transformed Eulerian Mean Theory

AbstractThe structure and stability of Jupiter’s atmosphere is analyzed using transformed Eulerian mean (TEM) theory. Utilizing the ammonia distribution derived from microwave radiometer measurements of the Juno orbiter, the latitudinal and vertical distribution of the vertical velocity in the interior of Jupiter’s atmosphere is inferred. The resulting overturning circulation is then interpreted in the TEM framework to offer speculation of the vertical and meridional temperature distribution. In the extratropics, the analyzed vertical velocity field shows Ferrel-cell-like patterns associated with each of the jets. A scaling analysis of the TEM overturning circulation equation suggests that in order for the Ferrel-cell-like patterns to be visible in the ammonia distribution, the static stability of Jupiter’s weather layer should be on the order of 1 × 10−2 s−1. In the tropics, the ammonia distribution suggests strong upward motion which is reminiscent of the rising branch of the Hadley cell where the static stability is weaker. Taken together, the analysis suggests that the temperature lapse rate in the extratropics is markedly greater than that in the tropics. Because the cloud top temperature is nearly uniform across all latitudes, the analysis suggests that in the interior of the weather layer, there could exist a temperature gradient between the tropical and extratropical regions.

Case study: Vertical distributions of both temperature and dissolved oxygen in Lake Diatas - Indonesia

Lake Diatas is one of the largest lakes in West Sumatra with a variety of uses that are vulnerable to contamination that could endanger lake organisms. Therefore, the objective of the present study is to describe the vertical distributions of both temperature and dissolved oxygen (DO) in Lake Diatas as an indication of lake quality. The samples of lake water were taken at five points, namely in the middle of the lake, Teluk Kinari, Muara Danau, Gurun Datar and in Tanduk Kecil. Frequency of taking was once a month in October, November and December 2019. Variation in depth for temperature and DO observations was based on the methods of surface-water sampling (SNI 6989.57: 2008). The present study results show that the temperature range at various points with respect to lake depth variation was 20.1 to 25.9 °C with a standard deviation of 1.15 °C, while DO was in the range of 6.2 to 7.9 mg/l. These conditions still met the quality standards of lake water (Governor Regulation No. 24 Year 2010 Class II) where the temperature deviation must be less than 3 °C, and the minimum DO is 4 mg/l. By using statistical method of the two-way ANOVA, it is found that the temperature was significantly different from the time of sampling with a P-value <0.05, but the temperature did not differ significantly based on depth. The sampling time and depth of collection differed significantly for DO at 2 points close to the agricultural land. It can be concluded that the temperature and DO in Lake Diatas were still good because the oxygen content was still sufficient to ensure the survival of lake organisms. In addition, there was no indication of thermal stratification in the lake.

Prediction of vertical thermal stratification of large space buildings based on Block-Gebhart model: Case studies of three typical hybrid ventilation scenarios

Although nozzle air supply is considered to be dominant when creating the thermal environment of the occupied area in a large space building, natural ventilation and air infiltration can interact with nozzle jets, resulting in a complex air distribution inside the building. This study focuses on the prediction of indoor vertical temperature distribution in large space buildings under the coupling of multiple airflows. Based on the validated regional model, Block-Gebhart (B-G) model, three auxiliary models were introduced for three types of common building ventilation scenarios, namely nozzle air supply, natural ventilation, and air infiltration. The auxiliary models were combined with the basic model to predict the indoor thermal environment of large space buildings in three hybrid ventilation scenarios. Field measurements of the vertical air temperatures of these three buildings were carried out to verify the feasibility and accuracy of the composite model. The results showed that the average deviations of air temperature in the International Gymnastics Stadium, the Ecological Demonstration Building and the Engineering Training Plant were 0.85, 0.80, and 0.32 °C, respectively. The building with the minimum deviation was the training plant, because the prediction of air temperature of this building took into account both jet entrainment and air infiltration phenomenon, so that the description of its indoor airflow pattern was the most accurate. The composite model proposed in this paper extends the application of the B-G model in hybrid ventilation scenarios and supplements the present design system of air distribution in large space buildings.

Research on vertical spatial characteristic of satellite infrared hyperspectral atmospheric sounding data

Spatial characteristic is an important indicator of remote sensor performance, and space-borne infrared hyperspectral sounder is the frontier of atmospheric vertical sounding technology. In this paper, the formation mechanism of the vertical spatial characteristics involved in the space-borne infrared hyperspectral sounding data are analyzed in detail, which shows that the vertical spatial characteristics of sounding data depends not only on the spectral channels and their waveband coverage, but also the specific atmospheric parameter and its specific variation interested. The indicators of vertical spatial characteristics are defined and their mathematical models are established based on the mechanism analyses. These models are applied to the vertical spatial characteristic evaluation of atmospheric temperature sounding for FY-4A GIIRS, which is the first space-borne infrared hyperspectral atmospheric sounder in geostationary orbit. It is concluded that FY-4A GIIRS can sound the vertical temperature distribution in whole troposphere and lower stratosphere with height < 35 km. This study can provide basic information to support the improvement of infrared hyperspectral sounder and the trace of vertical spatial characteristics of atmospheric inversion products.

The stellar distribution function and local vertical potential from Gaia DR2

ABSTRACT We develop a novel method to simultaneously determine the vertical potential, force, and stellar z−vz phase space distribution function (DF) in our local patch of the Galaxy. We assume that the Solar Neighbourhood can be treated as a one-dimensional (1D) system in dynamical equilibrium and directly fit the number density in the z−vz plane to what we call the rational linear distribution function (RLDF) model. This model can be regarded as a continuous sum of isothermal DFs though it has only one more parameter than the isothermal model. We apply our method to a sample of giant stars from Gaia Data Release 2 and show that the RLDF provides an excellent fit to the data. The well-known phase space spiral emerges in the residual map of the z−vz plane. We use the best-fitting potential to plot the residuals in terms of the frequency and angle of vertical oscillations and show that the spiral maps into a straight line. From its slope, we estimate that the phase spirals were generated by a perturbation ∼540 Myr years ago. We also determine the differential surface density as a function of vertical velocity dispersion, a.k.a. the vertical temperature distribution. The result is qualitatively similar to what was previously found for SDSS/SEGUE G dwarfs. Finally, we address parameter degeneracies and the validity of the 1D approximation. Particularly, the mid-plane density derived from a cold sub-sample, where the 1D approximation is more secure, is closer to literature values than that derived from the sample as a whole.

The Effect of the Horizontal Dimensions of Inland Water Bodies on the Thickness of the Upper Mixed Layer

The effect of the horizontal dimensions of inland water bodies (lakes and reservoirs) on the vertical mixing processes is studied. We consider a three-dimensional hydrostatic model and a one-dimensional LAKE model based on the averaging of three-dimensional equations over a horizontal section of the water body. The processes of vertical mixing in both models were simulated with the use of k–e-closure. LAKE model takes into account the seiches through the parameterization of the pressure gradient and horizontal viscosity. The models were verified against the Kato-Phillips experiment data, and a series of numerical experiments was carried out to demonstrate the effect of the horizontal size of the water body on mixed-layer depth. It is shown that the horizontal dimensions of a water body has to be taken into account in the simulation of the vertical temperature distribution in lakes and reservoirs with the size much less than the internal Rossby deformation radius.

Estimating the two-dimensional thermal environment generated by strong fire plumes in an urban utility tunnel

Although utility tunnels act as an innovative technique for the sustainable development of city’s utilities and limited underground space today, the fire issues in this type of tunnel should be carefully treated as they are different from traffic tunnel fire scenarios. In order to propose an easy-to-use two-dimensional (2D) temperature estimation methodology that is helpful to the designers, operators and firefighters, the temperature distributions and ceiling jet thickness (the vertical distance from the ceiling to where the temperature within the fire-induced smoke flow drops to half of its maximum at a certain location) were investigated with full-scale fire tests in a utility tunnel. The vertical temperature distributions were represented as a normalized single convex-concave profile. Self-similarity was confirmed and three types of similarity profiles were found. In order to correlate the inner boundary layer region and outer region of these ceiling jet flow profiles, a series of mathematical functions combining a power function and Gortler’s error function were employed. Furthermore, the ceiling jet thickness was found to vary as a power function with the longitudinal distance, rather than being a constant as previous research suggested. The vertical distribution model, the ceiling jet thickness model and the longitudinal temperature decay model were combined into a framework to empirically estimate the 2D thermal environment generated by strong fire plumes in utility tunnel’s fire protection engineering practice.

Observational study of the vertical aerosol and meteorological factor distributions with respect to particulate pollution in Xi'an

To understand the characteristics of atmospheric pollution in Xi'an, China, the vertical structure of aerosols and meteorological data (temperature and relative humidity) during atmospheric pollution processes were obtained and studied. Lidar and radiosonde data were used for analyses of atmospheric pollution. Polarization lidar was used to study the vertical distribution and optical properties of aerosols during haze and dust processes that occurred in 2015–2016. The planetary boundary layer height (PBLH) and types of aerosol particles were retrieved from polarization lidar. A case study shows that a low PBLH and complex vertical distributions of aerosols, temperature and relative humidity (RH) were the main structural characteristics of haze days. The backscatter coefficient exceeded 0.015 km−1·Sr−1, while the linear particle depolarization ratio was relatively small. A large depolarization ratio above the haze layer, which induces the existence of floating dust, was observed by polarization lidar. Compared with those of haze processes, the vertical aerosol and temperature distributions of dust processes were different. Statistical analyses of the PBLH, temperature inversion, RH and near-surface aerosol concentration were also presented. A lower PBLH, lower average lapse rate of temperature within the PBL, and higher RH were found when haze pollution occurred. An inversion at the top of the boundary layer aggravates ground pollution, while there is not always a temperature inversion when haze occurs in Xi'an. Together, a lower PBLH and lower average lapse rate of temperature weaken the vertical diffusion of pollutants. Decreased vertical diffusion should be the main reason for the formation and persistence of pollution in Xi'an. Increased RH was the catalyst for haze pollution. The aggravation of haze was usually accompanied by an increase in RH, and the decline of haze processes was also accompanied by a decrease or increase (>90%) in RH.