Vertical Profiles Of Air Temperature Research Articles

Retrieval of air temperature profiles in the Venusian mesosphere from VIRTIS‐M data: Description and validation of algorithms

We present here methods developed for the retrieval of air temperature profiles in the Venusian mesosphere from the absolute radiances measured by the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS) on board the Venus Express satellite. The infrared M channel of the instrument acquires multispectral images between 1000 and 5000 nm. In nighttime measurements, radiance in the range 3800–5000 nm is dominated by the thermal emission and absorption by the clouds and carbon dioxide. Since the latter is the main atmospheric component, it is possible to exploit the strong variability of its opacity in this spectral range, as resolved by the instrument, to reconstruct the vertical air temperature profile as a function of pressure. In this context we decided to adopt the Twomey et al. (1977) relaxation scheme. The resulting code was extensively tested on a set of simulated VIRTIS‐M data. Comparison of the known input conditions with the results of analysis code allowed us to evaluate the systematic and random errors affecting the retrievals procedures on a statistical basis. The code returns the vertical air temperature profile with an uncertainty of less than 1 K in the region between 70 and 7 mbar (66 and 77 km above the reference surface) and less than 4 K throughout the entire range 100–0.1 mbar (64–95 km). Finally, we present the first examples of the code applied to actual measured Venusian data, demonstrating its capability to achieve a satisfactory modeling of the observations and provide physically reasonable results.

Influence of a solar eclipse on thermal stratification and the turbulence regime

During the total solar eclipse on March 29, 2006 [1], researchers in Kislovodsk measured variations in the flux of the total shortwave radiation, meteorological elements (wind speed and direction and relative air humidity), and turbulence parameters in the surface atmospheric layer, vertical profiles of air temperature in the layer 0‐600 m, functions of particle size distribution (0.20‐1.50 µ m), and concentrations of light ions. It was found that the decrease in the maximum air temperature caused by the eclipse reached 3.5°C in the surface atmospheric layer and approximately 2°C at an altitude of 600 m a.s.l. After the full phase of the eclipse, turbulent kinetic energy decreased by a factor of 2.5, dispersion of the vertical component of the wind speed decreased by a factor of 2.3, turbulent heat flux decreased by a factor of 3.5, and dispersion of turbulent pulsations of air temperature decreased by a factor of 10. Despite the long history of investigations of eclipses [2], the influence of the solar eclipses on processes in the boundary atmospheric layer has not yet been studied sufficiently enough [3‐5]. It is clear that a solar eclipse should lead to variations in the thermal regime of the boundary atmospheric layer, increase in the relative air humidity, and consequent increase in the size of aerosol particles. Variations in the parameters of aerosol along with other factors can change notably the electric characteristics of the surface atmosphere [6]. Decrease in the near-surface air temperature can also lead to variations in the turbulence regime. In order to study the quantitative variations in the above-mentioned parameters of the lower atmosphere during the total solar eclipse in the last decade of March in Kislovodsk (altitude ~900 m a.s.l.), the following measurements were carried out at the urban meteorological station: flux F of total shortwave radiation (CNR1 net radiometer (Kipp and Zonen, Netherlands); accuracy ± 10 W/m 2 ), meteorological parameters (accuracy of measurements: air temperature ± 0.3°C , relative humidity ± 5% , components of wind speed ± 0.15 m/s), turbulent pulsations (digitization step 0.1 s) of three components of wind speed and air temperature using a Meteo-2M acoustic meteorological station (Institute of Atmospheric Optics, Tomsk), vertical profiles of air temperature (time averaging 5 min, spatial averaging 50 m, accuracy of measurements ± 0.5°C ) in layer 0‐ 600 m (MTP-5 UHF microwave profiler of the Central Aerological Observatory [8]), concentrations of negative light ions using a SIGMA-1 counter of aeroions (accuracy of each measurement ± 30% , time constant 1.5 s, mobility of ions >0.4 cm 2 / W · s), and distribution function of the dry base of aerosol particles in the size range 0.20‐1.50 µ m (LAS-P laser spectrometer of aerosols, averaging time of differential countable concentrations of particles 15 s, and random error of measurements of countable concentrations 20%). Calibration of the laser spectrometer was carried out using nuclear filters, which allowed us to increase the accuracy of determination of the boundaries of the particle size ranges determined by the spectrometer.

Airflow and heat flux through the vertical opening of buoyancy-induced naturally ventilated enclosures

Characteristics of the mean and turbulent airflow and heat flux through the vertical opening of a buoyancy-induced naturally ventilated full-scale enclosure with upper and lower vents on one of the sidewalls were studied experimentally. The effect of the interaction between the mixing and the displacement ventilation modes on the airflow through the upper vent is explored. Measurements include vertical profiles of mean and turbulent air velocity and temperature through the upper opening using a three-dimensional sonic anemometer. The airflow appears to be inclined to the horizontal plane due to the effect of buoyancy. The level of the neutral plane at the upper vent, defined here as the plane separating between inflow and outflow, can be identified by the vertical profiles of both mean flow and turbulence intensity, with good agreement between the two approaches. The contribution of the turbulent to the total (mean and turbulent) heat flux through the vent decreases as ventilation transforms from the mixing to the displacement mode.

The martian atmosphere in the region of Hellas basin as observed by the planetary Fourier spectrometer (PFS-MEX)

This work presents a review of the observations acquired by the planetary Fourier spectrometer (PFS) in the region of the Hellas basin. Taking advantage of the high spectral resolution of PFS, the vertical air temperature profile can be investigated with a previously unexperienced vertical resolution. Extensive comparisons with the expectations of EMCD 4.0 database highlight moderate discrepancies, strongly dependant on season. Namely, the morning observations acquired around L s=45° show a series of temperature deficiencies with recurrent spatial patterns in different observations, correlated with the topography profile. Trends of integrated dust loads as a function of the field of view (FOV) elevation are also described. Values are consistent with the retrieval hypothesis of a dust scale height equal to the gas one, even far from the season of main dust storms.

VERTICAL PROFILE AND TURBULENT DIFFUSIVITY OF AIR TEMPERATURE, CO2, and H2O WITHIN AND ABOVE A SUBURBAN CANOPY

This paper shows the seasonal dependency of vertical profile of air temperature, CO2, and H2O within and above a suburban canopy and the turbulent diffusivity of the scalars. The results were derived from field measurements of the vertical profiles and fluxes, which were conducted in a residential area (the mean height of canopy is 7.3 m) of Tokyo, Japan. The vertical profile of CO2 in the daytime drastically varied with the season; the CO2 concentration within the canopy was lower than that above the canopy in summer but was slightly higher in winter. The seasonal change of the daytime CO2 profile is likely due to the effect of photosynthesis by vegetation in backyards. The normalized turbulent diffusivity of air temperature and CO2 depended on height and atmospheric stability, which is similar to that for vegetated canopies. In contrast, the normalized turbulent diffusivity of H2O was relatively smaller than that of heat and CO2. Although the correlation coefficients indicated that the transfer efficiencies of CO2 were generally smaller than that of heat, the magnitude of normalized turbulent diffusivity of air temperature and CO2 was almost same.

WINTERTIME PROFILES OF TEMPERATURE, CO2, AND WATER VAPOR AND LOCAL COLD-AIR SUBSIDENCE IN A RESIDENTIAL AREA

In this study we focused on the relationships between the vertical profiles of scalar within and above a suburban canopy and the cold-air subsidence locally generated within the canopy. The results were derived from the wintertime field measurements of the vertical profiles of CO2, air temperature, water vapor, and turbulent flows, which were conducted in a residential area (the mean height of canopy is 7.3 m) of Tokyo, Japan. Under stably stratified conditions, the CO2 concentration above the canopy decreased with height, while that within the canopy kept almost same level. This indicates that the CO2 emitted from the houses accumulated within the canopy. Such behavior was not found in H2O profile. The vertical profile of air temperature and observations on the surface temperature using a thermal infrared camera suggested that the cold air generated at roof level moved down to the ground level. The effect of ‘cold air subsidence’ within the canopy is the most plausible reason for the nighttime vertical profiles of CO2 and H2O.

Flux-gradient profiles for momentum and heat over an urban surface

In this paper, we evaluate the applicability of flux-gradient relationships for momentum and heat for urban boundary layers within the Monin-Obukhov similarity (MOS) theory framework. Although the theory is widely used for smooth wall boundary layers, it is not known how well the theory works for urban layers. To address this problem, we measured the vertical profiles of wind velocity, air temperature, and fluxes of heat and momentum over a residential area and compared the results to theory. The measurements were done above an urban canopy whose mean height zh is 7.3 m. 3-D sonic anemometers and fine wire thermocouples were installed at 4 heights in the region 1.5zh < z < 4zh. We found the following: (1) The non-dimensional horizontal wind speed has good agreement with the stratified logarithmic profile predicted using the semi-empirical Monin-Obukov similarity (MOS) function, when it was scaled by the surface friction velocity that is derived from the shear stress extrapolated to the roof-top level. (2) The scaled gradient of horizontal wind speed \(\phi_M =(dU/dz)kz^\prime/u_{\ast}\) followed a conventional semi-empirical function for a flat surface at a level (z/zh = 2.9), whereas, in the vicinity of the canopy height \({\phi_M}^{-1}\) was larger than the commonly-used empirical relationship. (3) The potential temperature profile above the canopy shows dependency on the atmospheric stability and the scaled gradient of temperature \((\phi_H=(d\theta/dz){kz^\prime/T_{\ast}})\) is in good agreement with a conventional shear function for heat. In the case of heat, the dependency on height was not found. (4) The flux-gradient relationship for momentum and heat in the region 1.5zh < z < 4zh was rather similar to that for flat surfaces than that for vegetated canopies.

Methods for the analysis of data from the Planetary Fourier Spectrometer on the Mars Express Mission

This work presents an algorithm for the scientific analysis of individual calibrated measurements from the Planetary Fourier spectrometer (PFS). The instrument, included in the scientific payload of the ESA Mars Express mission to Mars, acquires spectra in the range between 250 and 8200 cm −1, with a sampling step of ∼1 cm −1 and an effective resolution of ∼2 cm −1. The observed radiance depends on several parameters of the atmosphere and surface of Mars as described by the radiative transfer equation. Adopting the very general formalism of Bayesian analysis, we determined which quantities are actually retrievable from individual measurements. Namely, they are: the surface temperature, the column density of dust and water ice aerosols in the atmosphere, the air temperature as a function of altitude (in the indicative range 5–45 km above the surface), the surface pressure, and the column density of water vapor and carbon monoxide. These evaluations are carried out taking into account the noise equivalent radiance (NER) of the instrument and the natural variabilities of the investigated parameters in the Martian environment, as estimated from the expectations of the European Martian Climate Dataset v3.1 (EMCD). Other parameters included in the radiative transfer equation shall be assumed as known, because they are not retrievable from individual measurements due to the instrumental NER or an underconstrained inverse problem: the surface emissivity in the thermal infrared, the optical properties of suspended dust and the analytical shape of dust concentration vs. altitude. During the development of the algorithm devoted to these studies, different approaches were evaluated on the basis of formal, computational and scientific considerations, with the aim to develop the general design of an integrated software package. The resulting code was extensively tested on a wide set of simulated PFS spectra. These spectra were computed from the atmospheric and surface conditions extracted from the EMCD, assumed to be representative of the Martian environment for different values of latitude, local time and season. Their comparison with the retrievals from simulated observations allowed us to evaluate the systematic and random errors affecting the procedures with respect to the different quantities involved. The code evaluates the surface temperature with an error in the order of 1 K, while the vertical air temperature profile is computed with an uncertainty less than 2 K from in the region between 5 and 20 km above the surface, increasing up to 7 K at 50 km. The column opacity of dust, measured in terms of integrated optical thickness at 1100 cm −1, is computed with an error of around 0.13. The surface pressure determination is carried out with a typical uncertainty of 0.2–0.3 millibar. Several auxiliary tests allowed us to study the correlations between the different retrieval errors and the possible causes of incorrect PFS data interpretation. The choice of a suitable model for the dust optical properties is demonstrated to be particularly critical. This paper also presents the first discussion about application of the procedure to actual PFS Martian data. Despite the calibration issues still affecting the determination of absolute radiance in the near-infrared, the algorithm is able to achieve a satisfactory modeling of observations in a wide range of situations.

Measurement of saltation process over gobi and sand dunes in the Taklimakan desert, China, with newly developed sand particle counter

The Japan‐Sino joint project, Aeolian Dust Experiment on Climate impact (ADEC), was initiated in April 2000 in order to understand the aeolian dust impact on climate via radiative forcing. As a part of the ADEC project, we have conducted field research in a sand dune and a gobi (i.e., a desert in which the soil surface consists of sand and pebbles with flat surfaces) in the south of the Taklimakan desert, China. The purpose of this study is to understand the wind erosion process and its relation to the meteorological and soil physical parameters. For this purpose, we measured the vertical profiles of wind speed, air temperature, and humidity as well as the other meteorological elements using an automatic weather station. A new sand particle counter (SPC) was newly developed to measure the saltation process. The SPC detects a signal change when a saltation particle passes through the slit between the laser beam transmitter and receiver. From this signal change, we can measure saltation particles from 30 to 667 μm diameter with 32 bin classes and particle numbers of each bin class every second. We have operated this SPC in the field, and it proved to be useful for the saltation process study when data corrections and calibration were properly made. During the observation period (1–21 April 2002), a total of eight dust events occurred; we analyzed two events: 5 April and 14 April cases. The results can be summarized as follows: (1) Total saltation fluxes in the 5 April case from 1223 to 1430 UT were 37.93 kg m−2 at 30 cm height and 43.71 kg m−2 at 20 cm height for the gobi site and 2.61 kg m−2 at 30 cm height for the dune site. (2) In the 14 April case, from 0327 to 0830 UT, the total saltation flux was 8.95 kg m−2 at 30 cm height for the gobi site. (3) Saltation flux at the gobi site in the 5 April case was more than 10 times larger than that of the sand dune, though the distance between the sites is 4 km. This is because the number of the parent soil particles around 80 μm at the gobi site was more than 10 times greater than that of the dune site. (4) Height dependency of saltation particle size and number was found in the gobi site; that is, the particle size distributions at the gobi sites in the 5 April case indicated that the number size distribution of the coarse particles, 117 to 554 μm, at 20 cm height was greater than that at 30 cm height. This size‐height dependency was reasonable from a physical point of view. However, present theory cannot explain this well.

Ice-shelf microtopography observed using satellite thermal imagery

AbstractSmall anomalies in ice-shelf surface temperature correlate with measured microtopography. Clear-sky thermal infrared (TIR) images of the Brunt Ice Shelf, Antarctica, frequently show persistent patterns of anomalous snow surface temperatures. The anomalous signatures appear as stripes orientated along the ice flowline and are of the order of 5 K in magnitude. The positional persistence of the stripes suggests a topographic mechanism for their formation. In order to test this hypothesis, the TIR stripes are compared to a digital terrain model (DTM) derived from a kinematic global positioning system survey of the ice shelf. Ridges and valleys are seen in the DTM; the ridges correspond to the warmer TIR stripes, the valleys to the colder areas. In order to investigate the mechanism that couples elevation with thermal signature, two comparable but contrasting sets of clear-sky infrared images are presented, along with surface meteorological data. The first shows strong TIR stripes, whilst the second, despite similar snow- and air-temperature profiles, shows a weaker signature and smaller sensible-heat flux, H. Two possible mechanisms are presented which explain the TIR signature: surface elevation mapping onto the vertical air-temperature profile or, alternatively, enhanced surface sensible-heat flux on elevated areas. At present, there is insufficient information to resolve this uncertainty.

Mean vertical profiles of temperature and absolute humidity from a 12-year radiosounding data set at Terra Nova Bay (Antarctica)

A set of 1330 radiosoundings was performed at the Italian station of Terra Nova Bay in Antarctica during 12 measurement campaigns from 1987 to 1998. These measurements were separately analyzed for the various 10-day periods from mid-October to mid-February, to determine the mean vertical profiles of air pressure and temperature in the troposphere and lower stratosphere, and those of moisture parameters in the troposphere. The temperature data were corrected for the errors due to radiation and heat exchange processes and for the lag errors of the sensor. Due to temperature dependence and other dry bias effects, the humidity errors were also taken into account. The tropospheric temperature was found to present average values of its vertical gradient varying between −5.4 and −6.3 K/km, while its minimum height associated with the tropopause gradually lowered from 13.7 to 7.9 km. Total water vapor content increased correspondingly from 0.12 to 0.36 g cm −2 during the first two months and decreased to 0.26 g cm −2 in the following period. Stratospheric temperature was observed to increase during the first 2 months by about 15 K in the region below the 24-km height and to appreciably decrease at upper levels, maintaining almost stable features during the subsequent months.

Canopy Architecture and Turbulence Structure in a Coniferous Forest

Synchronous sonic anemometric measurements at five heightswithin a mixed coniferous forest were used to test two different parameterisations ofcanopy architecture in the application of a second-order turbulence closure model. Inthe computation of the leaf drag area, the aerodynamic sheltering was replaced with anarchitectural sheltering, assumed to be analogous to the clumping index defined in radiativetransfer theory. Consequently, the ratio of leaf area density and sheltering factor was approximatedby the effective leaf area or the mean contact number, both obtained from the inversion of non-destructive optical measurements. The first parameter represents the equivalentrandomly dispersed leaf area in terms of shading, the second is the average number of leavesthat a straight line intercepts penetrating the canopy with a certain zenith angle. Theselection of this direction was determined by the analysis of the mean angle of the wind vectorduring sweep events. The drag coefficient values obtained from the inversion of themomentum flux equation, using the two proposed parameterisations, are in good agreement withvalues found in the literature. The predicted profiles of turbulence statistics reasonablymatch actual measurements, especially in the case of the mean contact numberparameterisation. The vertical profile of leaf drag area, obtained by forcing the turbulence modelto match the observed standard deviation of vertical velocity (σw), is intermediatebetween the two empirical ones. Finally, the proposed canopy parameterisations were appliedto a Lagrangian transport model to predict vertical profiles of air temperature, H2O andCO2 concentration.

Microclimatological characteristics of a miscanthus (Miscanthus cv. giganteus) stand during stable conditionsat night in the nonvegetative winter period

¶Microclimatological data obtained during a field experiment in the nongrowing winter period were used to study the microclimatologically stable night conditions of a 200 × 150 m miscanthus (Miscanthus cv. giganteus) stand and compared to open field conditions. The microclimatological pattern within the miscanthus canopy was characterized by long-wave radiative cooling of the plant stand and by an established temperature inversion within the canopy at calm nights. The results show that there are significant differences in air temperature and energy balance components between the open field and the miscanthus field during calm and clear nights. In general, net radiation difference during the cold and calm nights was relatively constant and about 20 W m−2 less negative in miscanthus (because of lower surface temperatures) than at the open field. Air temperature differences also remained fairly constant and were up to 3 °C lower than at the open field (at the height of 1 m). Through thermal inversion cold air accumulated in the lower parts of the canopy as shown by the vertical air temperature profiles. They showed a greater amplitude within the diurnal cycle in the miscanthus stand than in the open field. Through the onset of wind, temperature profiles changed rapidly and differences diminished. Vertical katabatic air drainage into the canopy layers was estimated indirectly by using the energy balance approach. It was calculated from the significant energy balance closure gap and showed a mean air exchange rate of up to 22 m3 m−2 h−1, related to a stand volume of 1 m2 area and 4 m height, during the mostly calm and clear nights, depending on the canopy net radiation and turbulent heat exchange forced by slight wind spells. Quantitative uncertainties in calculated cold air drainage which are introduced by the measurement method and certain assumptions in the calculations, were considered in a sensitivity analysis. In spite of these uncertainties evidence of katabatic cold air flow is given.

Moisture supply and microclimate––interactions with productivity potential

Micrometeorological conditions within a crop canopy are important as direct environmental forces to photosynthesis and also for different microorganisms living in the plant ecosystem. Vertical profiles of air temperature, humidity, wind speed describe the micrometeorological conditions within the plant canopy. Those profiles depend on macrometeorological conditions and the structure and water status of the plant stand. A user friendly version of crop micrometeorological simulation model was developed concerning data assimilation and output analysis. The effect of soil moisture content was investigated on microclimatic conditions and further effects on photosynthesis intensity using simulation model. Different states of water supplies cause different measure of evapotranspiration and these differences appear in microclimate and formation of plant production.

History of the Long Series of Daily Air Temperature in Padova (1725–1998)

The history of the origin of the study of meteorology in Padova and its connection to the major developments of this science in Italy and the international context are presented. Special topics are: the scientific legacy of Galileo Galilei and the Accademia del Cimento,the birth of the first meteorological networks, i.e., Ferdinand II and Leopold de' Medici who created the Rete Medicea, J. Jurin and the network of the RoyalSociety, London, L. Cotte and the Societe Royale de Medicine, Paris, J. J. Hemmerand the Societas Meteorologica Palatina, Mannheim. After outliningthe cultural background that favoured the development of meteorology, emphasis is given to the plurisecular time series of meteorological observations, taken in Padova since 1725, in its national and international context. This long series includes barometric pressure, air temperature, wind direction and speed; state of the sky and occurrence of meteorological events and precipitation. Special reference is made to indoor and outdoor temperature observations. Solar radiation falling on each exposure has been modelled in order to know when data were fully reliable and when they were less so. A vertical profile of air temperature has allowed corrections of the change of instrument level, when necessary. In terms of homogeneity, the series can be divided into several periods, during which instruments and operational methods, position, general criteria were unchanged: origins in homes of the first observers (1725–1767); the First Period at the Specola(1768–1812); the Second Period at the Specola (1813–1864); the Third and Fourth Periodsat the Specola (1865–1937); the Last Measurements at theSpecola (1938–1962); the Giovanni Magrini Observatoryof the Water Magistrate (1920–today); the Gino Allegri Airport(1926–1990), the Botanical Gardens (1980–today), the CNR (1984–1986; 1993–today). The latestperiod with the birth of new weather stations, is the most affected byanthropic effect. The simultaneous presence of an urban and a rural weather station pointed out local effects which dominate the urban heat island.

Nocturnal Air Temperature Variations between Forest and Open Areas

Abstract In this study a variety of instruments were set up to examine the influence of net radiation, cold-air advection, and sheltering on the air temperature pattern in a coniferous forest during clear nights. The air temperature pattern in the forest was compared with both a neighboring large open area (>10 km2) and small open areas (<1 km2) within the forest. Vertical and horizontal air temperature profiles, mobile measurements of air temperature, and field stations measuring wind and air temperature at several levels were used to describe the air temperature development and air temperature pattern in the forest. The study showed that the correlations among sky view factor (SVF), net radiation, and air temperature were large for points within the forest. Increasing SVF gave a more negative net radiation and lower air temperature. In comparison with the extensive open areas, however, the forest had lower air temperatures even though SVF was lower. The results suggested that the lower air temperatures ...

久住山麓の草地斜面上で観測された冷気の流下層（ＣＡＤＬ）の構造とシアーフロー不安定性

Intensive observations of surface wind, longwave radiation and vertical profile of air temperature including surface temperature were made on a grass-covered slope of Mt. Kuju, Oita, Japan, during the period 21-27 August 1998, from which we obtained the following results.The cold-air-drainage layer (CADL), which is defined as the surface air layer on a slope with a potential temperature deficit, is made up of two sublayers, a radiation cooling underlayer (RCL) and a mixing cooling upper layer (MCL). Although the potential temperature deficit in the RCL is created by radiation cooling, that in the MCL is conjectured to be mainly caused by mixing of the cold air produced in the RCL with the air above, because the deficit increases even while the potential temperature keeps rising in the MCL. Owing to the shear flow instability, which can arise at the interface between the CADL and the overlying air where large shear occurs, the thickness of the MCL changes drastically, while the thickness of the RCL remains almost constant in time. When instability develops, an increase of potential temperature occurs in the MCL and often even in the RCL for a short time, due to the entrainment of the air with higher potential temperature from above.

The Diurnal Vari ation of Summer Surface Temperaturesin Meiji- shrine/Yoyogi-park and Its Peripheral Area

In the beginning of August, 1997 under typical summer pressure patterns, we observed an intensive observation. Using the portable thermal infrared camera, thermal infrared images were taken from Meijishrine/Yoyogi-park of Tokyo that was a large-scale green tract, and its peripheral area. The thermal infrared camera was setted by 1 on top of the Tokyo Metropolitan Government building and the roof of Shibuya-ku Office, and thermal infrared images were taken by an interval for ten minutes. Between synchronism, we lifted up a captive balloon from the central part of Yoyogi-park and measured vertical profiles of air temperature. We understood a difference of the thermal quality caused by the green tract and the artificial heat structure with concrete and the asphalt which constituted urban area from the diurnal variation of surface temperatures provided from thermal infrared images had. The difference of surface temperature between the green tract and its peripheral area reached about 7 degrees at the maximum. The surface temperature of multistory buildings became lower than the urban area in the daytime, whereas it was higher than there in the nighttime.

Sudden Change of Surface Inversion of Air Temperature on Suburban Area in the Chiba Prefecture

Vertical profile of air temperature is measured by radiosonde set on anchored balloon at a winter night, 3-4 December 1979, under the condition of clear sky and gentle wind. The observations were made at four points distributed in about 15km distance, in northwestern Chiba Prefecture (Fig. 1).Surface inversion appeared before sunset (about 15:30JST). Intensity of inversion increased to midnight and the depth of inversion layer reached 50-75m at midnight. Between 0 to 1JST temperature profile showed sudden change; strong inversion layer is elevated to 50-100m hight and ground based isothermal layer appeared under 50m bight (Fig. 2, 3). The similer change of temperature profile appeared at three suburban observation points except at one point placed in flat grass field. Concentration of NO and NO2 are high within the inversion layer and their vertical profile show simultaneous change with that of inversion (Fig. 4, 5).It is shown by wind field analysis, that the cold northern wind causes the change of temperature profile. The wind is a part of land breeze from Kanto Plain to the Tokyo Bay (Fig. 6, 7). These phenomena appeared at 34 nights during December of 1975-1979 (Table 1, 2 and Fig. 8), which correspond to the occurence frequency of about a half number of nights with clear sky and gentle wind.

Effects of thermal radiation on airflow with displacement ventilation: an experimental investigation

Various wall surface emissivities are used to examine the radiative effects on the vertical air temperature profile and gravity current in a full-scale model of a room ventilated by displacement. The vertical temperature stratification is a combined effect of convection, conduction and radiation. The radiative effects are to heat the floor surface and alter the flow rate in the thermal plumes, which weakens the gravity current and lowers the stratification level. The intermittance at the upper edge of the gravity current is illustrated by studying its turbelent structure. The data gathered in this work are suitable for validating flow and radiation models.