Horizontal Temperature Fields Research Articles

Indoor Thermal Environment Test of Six Prism Terrace Greenhouse

Solar greenhouse occupies a large proportion of greenhouse types in China and is the most widely used agricultural facility in northern China. The application of solar greenhouse in agriculture is mainly to cultivate fruits, vegetables and flowers, and the bottom surface of greenhouse is mainly rectangular. So in this paper, based on regular hexagon, a greenhouse with hexagonal structure is designed, and a miniature model is constructed according to the scale. Then select some reasonable components and install them inside the structure for temperature test. By measuring the temperature inside the greenhouse at a fixed point, the temperature change inside the greenhouse in a day is obtained. Through the analysis of the longitudinal temperature comparison and the horizontal temperature field inside the greenhouse, the rationality of the structure model is verified.

The Namib Turbulence Experiment: Investigating Surface–Atmosphere Heat Transfer in Three Dimensions

Abstract The Namib Turbulence Experiment (NamTEX) was a multinational micrometeorological campaign conducted in the central Namib Desert to investigate three-dimensional surface layer turbulence and the spatiotemporal patterns of heat transfer between the subsurface, surface, and atmosphere. The Namib provides an ideal location for fundamental research that revisits some key assumptions in micrometeorology that are implicitly included in the parameterizations describing energy exchange in weather forecasting and climate models: homogenous flat surfaces, no vegetation, little moisture, and cloud-free skies create a strong and consistent diurnal forcing, resulting in a wide range of atmospheric stabilities. A novel combination of instruments was used to simultaneously measure variables and processes relevant to heat transfer: a 3-km fiber-optic distributed temperature sensor (DTS) was suspended in a pseudo-three-dimensional array within a 300 m × 300 m domain to provide vertical cross sections of air temperature fluctuations. Aerial and ground-based thermal imagers recorded high-resolution surface temperature fluctuations within the domain and revealed the spatial thermal imprint of atmospheric structures responsible for heat exchange. High-resolution soil temperature and moisture profiles together with heat flux plates provided information on near-surface soil dynamics. Turbulent heat exchange was measured with a vertical array of five eddy-covariance point measurements on a 21-m mast, as well as by collocated small- and large-aperture scintillometers. This contribution first details the scientific goals and experimental setup of the NamTEX campaign. Then, using a typical day, we demonstrate (i) the coupling of surface layer, surface, and soil temperatures using high-frequency temperature measurements, (ii) differences in spatial and temporal standard deviations of the horizontal temperature field using spatially distributed measurements, and (iii) horizontal anisotropy of the turbulent temperature field.

Continuously sensing of water temperature in a lake using acoustic tomography method

ABSTRACT Continuously sensing of water temperature is of critical importance to water environment, fluid dynamic and water resources researches. Coastal acoustic tomography (CAT) is a remote sensing technique in spatial temperature distribution estimating and has been widely used in many coastal regions. Continuous observations of water temperature in small-scale waters with distance less than 1 km are seldom conducted, as it is difficult to get high-resolution observation results. Here, a horizontal temperature field within 300 m distance was mapped in a sound transmission experiment with three 50 kHz CAT systems. The maximum inversion error temperature for the horizontal temperature field was 0.09°C. The root-mean-square error between the CAT-observed and range-averaged temperature that were calculated from one-way travel time data along three transmission paths were 0.03°C, 0.028°C and 0.043°C, respectively. The obtained results confirmed that CAT can be used in recovering the horizontal distributions of water temperature fields in lake.

Water Temperature Observation by Coastal Acoustic Tomography in Artificial Upwelling Area

Artificial upwelling is a geoengineering method to repair and improve marine ecosystems, and its operation requires long-term and continuous temperature field observation. However, existing methods are rarely seen to accomplish such observation. In this study, we investigate the coastal acoustic tomography (CAT) to obtain the long-term horizontal temperature field of an artificial upwelling area in an anechoic tank. We conduct four sets of experiments with different CAT station numbers and compare their data with those collected from temperature sensors. By analyzing the travel time from the CAT experiments, the horizontal temperature field of the upwelling area could be mapped. The CAT results and the comparison results show that the surface temperature of the observed area decreases by approximately 3 °C after upwelling, while the temperature of where the CAT is deployed decreases by about 1 °C; the temperature is lowest at the center of the upwelling area. Increasing the number of stations and station spacing would improve the temperature mapping accuracy. Therefore, the feasibility of using the CAT system to observe artificial upwelling is proved valid. This study indicates the potential application of CAT in temperature field observation in artificial upwelling area in the sea.

Horizontal diffusive motion of columnar vortices in rotating Rayleigh–Bénard convection

In laboratory experiments, horizontal translational motion of columnar vortices formed in rotating Rayleigh–Bénard convection was investigated. Two types of measurements, vertical velocity fields and horizontal temperature fields, were conducted with water as the test fluid. Using particle image velocimetry, the vertical velocity fields determined the parameter range at which the quasi-two-dimensional columnar vortices emerged. Locally, the duration characteristics of the columns, evaluated with their vertical coherence, indicate the minimum time scale of translational motion of the vortices in the horizontal plane. Vortex tracking of the horizontal temperature fields over long observation periods (${>}10^{3}~\text{s}$) was conducted using encapsulated thermochromic liquid crystal visualization. Two cylindrical vessels with different radii showed the emergence of the centrifugal effect in $O({>}10^{2}~\text{s})$ despite the small Froude number ($Fr<0.1$). Further, in the horizontal plane the columnar vortices behaved in a random-walk-like diffusive motion. The statistically calculated mean-squared displacements indicated anomalous diffusive motion of the columns; displacement increasing with time as $t^{\unicode[STIX]{x1D6FE}}$ with $\unicode[STIX]{x1D6FE}\neq 1$. We discuss the causes of this anomaly in both the instantaneous and long-term statistical data gathered from experimental observations over different time scales. The enclosure effect from the repulsion of up-welling and down-welling vortices ensures that vortices diffuse only little, resulting in a sub-diffusive (decelerated) motion $\unicode[STIX]{x1D6FE}<1$ in $O(10^{1}~\text{s})$. With this weak centrifugal contribution, the translational motion of the columns slowly accelerates in the radial direction and thereby yields a super-diffusive (accelerated) motion $\unicode[STIX]{x1D6FE}>1$ in $O(10^{2}~\text{s})$.

Vortex tracking on visualized temperature fields in a rotating Rayleigh–Bénard convection

We established a vortex detection method using instantaneous temperature fields that were visualized using thermochromic liquid crystals (TLCs) to investigate behaviors of vortical structures in a rotating Rayleigh–Benard convection. Experimental testing was performed at a fixed Rayleigh number $$Ra = 1.0 \times 10^7$$ and different Taylor numbers from $$Ta = 1.0 \times 10^6$$ to $$1.0 \times 10^8$$ in water containing encapsulated TLCs. Vortices were recognized as undulations that appear in the horizontal temperature fields, thus making vortex detection with high spatial resolution possible, and this enabled quantitative investigation of the dynamics of vortical structures. Standard template matching was used to detect individual vortices on visualized temperature fields, and two-dimensional curved surface fitting was adopted to remove erroneous detections and to evaluate shapes of local temperature fields corresponding to vortical structures. Additionally, vortex tracking clearly showed geometric advection pattern of vortical structures.

Temperature disturbances in the subauroral lower thermosphere during winter stratospheric warming

Irregular variations in the temperature of the subauroral lower thermosphere during the winter stratospheric warming, which began in the first decade of December 2001 and continued to the end of the observational season (February 19, 2002), have been analyzed. The temperature measurements were based on the thermal broadening of the 557.7 nm oxygen emission measured during moonless nights at Maimaga optical station in the vicinity of Yakutsk (ϕ=63°N, λ=129.7° E) using the Fabry-Perot spectrometer. Isolated fragments of the map of contour lines of the horizontal temperature field and the globally averaged height-time section of the temperature at the levels of the 1, 2, 5, 10, 30, 50, and 70 hPa isobaric surfaces, obtained by the NOAA Meteorological Satellite Systems, as well as the F10.7 and Ap indices have been used to analyze the cause-effect relation between the variations in the temperature of the subauroral lower thermosphere and winter stratospheric warming events. It is shown that, when warming is detected at heights of the lower thermosphere, the temperature can become higher than its model values by up to 20 K, which indicates that the planetary waves can penetrate to heights of the lower thermosphere and then propagate downward. In this case the atmosphere cools at heights of the lower thermosphere and tends to heat up above 10 hPa and to cool below 30 and 50 hPa; i.e., we observe the well-known fact of vertical alternation of cold and warm atmospheric regions detected during winter stratospheric warming events.

310 内部発熱対流における温度場の可視化と解析(S42-1 流れの可視化実験解析(1),S42 流れの可視化実験解析)

Natural convection in a shallow fluid layer induced by internal heat generation was investigated experimentally. A horizontal temperature field at each Rayleigh number was visualized by Thermo-chromic Liquid Crystal (TLC), and then the obtained images were converted to the temperature field by a calibration curve, which correlates between color information extracted from the image and temperature. Individual cells were extracted from the converted temperature field and a variation of area of the cells with respect to the Rayleigh number represented a cell dilatation. Variations of statistical values, standard deviation of the temperature field and mean size of a cell, with Rayleigh number increases showed that there might be a gradual transition of the convection.

The spring transition from horizontal to vertical thermal stratification on a midlatitude continental shelf

The spring transition from wintertime horizontal thermal stratification to the summertime vertically stratified state on a wide, sloping midlatitude continental shelf is investigated. The sigma z‐level model (SZM), a new three‐dimensional primitive equation numerical ocean model employing a hybrid sigma coordinate and z‐level coordinate in the vertical, simulates the continental shelf region. A simple analytical model to describe the heating rate of a well‐mixed water column is applied to the problem to illustrate the importance of bottom slope in determining the evolution of the horizontal thermal stratification. The applicability of this simple model to continental shelf dynamics forced by realistic surface fluxes is studied with a “pseudo” two‐dimensional (x‐z) form of the SZM forced with daily heat flux and wind stress records from the West Florida Shelf. A term‐by‐term analysis of the depth‐averaged time‐integrated temperature equation quantifies the contribution of each physical process to the evolution of the horizontal temperature field. The simple model used to describe the heating rate of a homogeneous water column appears as the dominant balance in the integrated temperature equation. Cross‐shelf temperature advection associated with upwelling and downwelling alters the horizontal depth‐integrated temperature over the shelf predicted by the simple model. Two processes describe the spring transition. The erosion of the wintertime horizontal thermal gradient occurs on a timescale of a few months when the water column is being heated and mixed periodically. The second process is the formation of the seasonal thermocline following the last strong mixing event. This occurs on a timescale of less than a week under a stabilizing heat flux and light winds completing the spring transition from horizontal to vertical thermal stratification.

Near surface spatially averaged air temperature and wind speed determined by acoustic travel time tomography

Acoustic travel time tomography is presented as a possibility for remote monitoring of near surface air temperature and wind fields. This technique provides line-averaged effective sound speeds changing with temporally and spatially variable air temperature and wind vector. The effective sound speed is derived from the travel times of sound signals which propagate at defined paths between different acoustic sources and receivers. Starting with the travel time data a tomographic algorithm (Simultaneous Iterative Reconstruction Technique, SIRT) is used to calculate area-averaged air temperature and wind speed. The accuracy of the experimental method and the tomographic inversion algorithm is exemplarily demonstrated for one day without remarkable differences in the horizontal temperature field, determined by independent in situ measurements at different points within the measuring field. The differences between the conventionally determined air temperature (point measurement) and the air temperature determined by tomography (area-averaged measurement representative for the area of the measuring field 200 m x 260 m) were below 0.5 K for an average time of 10 minutes. The differences obtained between the wind speed measured at a meteorological mast and calculated from acoustic measurements are not higher than 0.5 m s -1 for the same averaging time. The tomographically determined area-averaged distribution of air temperature (resolution 50 m x 50 m) can be used to estimate the horizontal gradient of air temperature as a pre-condition to detect horizontal turbulent fluxes of sensible heat.

Simple Model Prediction of Horizontal Temperature Fields in the Subtropical–Subpolar System Caused by Sudden Change in Wind Stress Curl

Abstract A four-level numerical model, which is driven by wind stress and surface heat flux, is used to study responses of horizontal temperature fields in the subtropical–subpolar system to a sudden change in the magnitude of the wind stress curl. Weakly nonlinear responses to O(1) change in the wind stress curl are examined, according to the effects on the Ekman pumping, convection, westward baroclinic wave, and advection. For this purpose, a quasi-analytical method, that is, characteristics associated with effects of both wave propagation and advection, is constructed based on a planetary geostrophic model with four-level geometry. Characteristics obtained for the first and second baroclinic modes are used to diagnose steady-state and time-dependent solutions. One feature of time-dependent motions predicted by the model is a westward propagation of the first baroclinic mode with a significantly higher speed than the combined speed of the nondispersive first-mode baroclinic Rossby wave and barotropic ci...

A note on the use of acoustic Doppler current profilers in mesoscale surveys

The mesoscale structure of the Arctic Front in the Greenland Sea has been investigated during three surveys using acoustic Doppler current profiling and hydrographic measurements. It is shown that systematic errors of the current measurements that are related to the ship's speed can be reduced significantly by an appropriate calibration, and that the vessel's navigation remains the main limiting factor in obtaining accurate estimates of absolute currents. However, in regions where the temperature distribution can be assumed to correspond to the density distribution, vertical shear measurements compare favorably with the horizontal temperature fields so that they prove to be a useful tool for high-resolution mesoscale investigations. >

Experimental determination of 2-D flame temperature fields by interferometric tomography

An optical method for measuring the 2-D temperature distribution in a horizontal plane of an asymmetric diffusion flame is studied. Using a Mach-Zehnder interferometer the method records projections of the index of refraction in the flame from eight different directions. The projection data are detected by a 1024 channel linear diode array and are then transferred to a computer which reconstructs the 2-D distribution of the refractive index and temperature by methods known from computer tomography. All data processing is governed by an interactive computer program. The tomographic reconstruction is performed by the iterative algorithm MART (multiplicative algebraic reconstruction technique), which has been modified to minimize the reconstruction errors for this type of application. The results indicate that it is possible to reconstruct the horizontal temperature field of an asymmetric and moderately hot slot flame using few (i.e. less than 10) projection angles with temperature errors less than ±10%.

SYNOPTIC USE OF RADIATION MEASUREMENTS FROM SATELLITE TIROS II1

TIROS II measurements of infrared radiation in the 10-micron “water-vapor window” on one orbital pass over the United States are examined in detail relative to the field of cloudiness as derived from TIROS II television pictures and from other meteorological data. The radiation data are found to portray clearly the large-scale systems of middle and dense high cloud overcast, a capability that exists both day and night. Through use of information about the vertical and horizontal temperature fields, useful quantitative estimates of the heights of the tops of cloud systems are derived. In cases where there is a low overcast, the window measurements in themselves may not distinguish clouds from clear areas; but during daytime if television pictures are available, the window measurements can clearly show where a cloud overcast is low in height. Some tentative conclusions about the partial transparency of cirrus clouds to infrared radiation are also presented.

LEE-SIDE FRONTOGENESIS IN THE ROCKY MOUNTAINS1

Abstract The development and motion of fronts associated with lee-side troughs on large mountain barriers has been investigated. These fronts differ from ordinary cold fronts in their horizontal temperature field, which is characterized by a sinusoidal thermal ridge. The thermal ridge intensifies, while remaining stationary with respect to the mountains, and moves eastward upon the approach of a Pacific cold front. An equation is derived, showing that changes in the thermal pattern can be described by changes in a potential thermal vorticity equation, which consists of three terms: (1) one representing an advection of the potential thermal vorticity by the 500-mb. wind; (2) one representing the advection of 500-mb. absolute vorticity by the thermal wind; and (3) a purely orographic term. An idealized sinusoidal model of the thickness pattern is used in conjunction with the prognostic equation to explain the development and motion of lee-side thermal ridges. Actual examples from synoptic maps are chosen to...