Temperature Standard Deviation Research Articles

Picosecond-lidar thermometry in a measurement volume surrounded by highly scattering media

In this work, a picosecond-lidar system, using a Nd:YAG picosecond laser, a Newtonian telescope and a streak camera, was used for single-ended furnace diagnostics. The optical access of the furnace was obstructed by a sooty diffusion ethylene flame. It was demonstrated that, with proper optical arrangement, the elastic scattering of the flame can be mapped in one dimension simultaneously as temperatures, up to 1200 K, are measured in the furnace using Rayleigh thermometry. Accumulated point temperature measurements as well as one- and two-dimensional measurements were conducted. A discussion about noise influence on accuracy and precision shows that measurements allowing a resolution of ∼6 cm are possible with a single-pixel temperature standard deviation of 91 K, while mapping soot scattering from the flame within the dynamic range of the streak camera, using 30 mJ pulse energy.

Predictions of beta diversity for reef macroalgae across southeastern Australia

We analyzed and predicted spatial patterns of turnover in macroalgal community composition (beta diversity) that accounted for broad-scale environmental gradients using two contrasting community modelling methods, Generalised Dissimilarity Modelling (GDM) and Gradient Forest Modelling (GFM). Percentage cover data from underwater macroalgal surveys of subtidal rocky reefs along the southeastern coastline of continental Australia and northern coastline of Tasmania were combined with 0.01°-resolution gridded environmental variables, to develop statistical models of beta diversity. GDM, a statistical approach based on a matrix regression, and GFM, a machine learning approach based on ensemble tree based methods, were used to fit models and generate predictions of beta diversity within unsurveyed areas across the region of interest. Patterns of macroalgal beta diversity predicted by both methods were remarkably congruent and showed a similar and striking change in community composition from eastern South Australia to western Victoria and northern Tasmania. Macroalgal communities differed markedly in predicted composition between the open coast and inshore locations. A distinct algal community was predicted for the enclosed Port Philip Bay in Victoria. Sea surface temperature standard deviation and average contributed most to changes in beta diversity for both the GDM and GFM models; changes in wave exposure and oxygen also influenced beta diversity in the GDM model, while salinity and exposure contributed substantially to the GFM model. The GDM and GFM analyses allowed us to model and predict spatial patterns of beta diversity in macroalgal communities comprising >180 species over 6600 km of coastline. These outputs advance regional-scale conservation management by allowing planners to interpolate from point source ecological data to assess the distribution of biodiversity across their full domain of interest. The congruence between methods suggests that strong environmental gradients related to temperature and exposure are the common drivers of community change in this region.

Unveiling the 3D temperature structure of galaxy clusters by means of the thermal Sunyaev-Zel’dovich effect

The Sunyaev-Zel'dovich (hereafter SZ) effect is a promising tool to derive the gas temperature of galaxy clusters. The approximation of a spherically symmetric gas distribution is usually used to determine the temperature structure of galaxy clusters, but this approximation cannot properly describe merging galaxy clusters. The methods used so far, which do not assume the spherically symmetric distribution, permit us to derive 2D temperature maps of merging galaxy clusters. In this paper, we propose a method to derive the standard temperature deviation and temperature variance along the line-of-sight, which permits us to analyze the 3D temperature structure of galaxy clusters by means of the thermal SZ effect. We also propose a method to reveal merger shock waves in galaxy clusters by analyzing the presence of temperature inhomogeneities along the line-of-sight.

Air pollution, weather variations and primary spontaneous pneumothorax.

Spontaneous pneumothoraces (SP) tend to occur in clusters which have been related to atmospheric pressure variations and thunderstorm insurgence. We examined the influence of standard meteorological parameter variations and concentrations of the major air pollutants on incidence of spontaneous pneumothorax (SP) in a highly developed industrial area (Turin, Italy). From October 2002 to December 2007, 591 SP patients were prospectively evaluated. For each day, standard weather parameters and concentration of air pollutants were recorded. The total number of admissions for SP was 591. The number of days with admissions was 363, which represents the 19% of the total number of days in the study period (1918). Eighty-one percent of days with SP admissions were clusterized. Results of statistical analysis showed that the sequence of SP events was not random. There was relationship between SP and daily wind speed (WS) minimum, daily standard deviation of NO(2), NO(2), CO(2) daily maximum and minimum, O3 daily minimum, daily mean CO(2) (p = 0.01), daily NO(2) minimum (p = 0.001). Multiple regression analysis has shown relationship between number of SP admissions and increase of daily mean and minimum NO(2) (p = 0.001), decrease of NO(2) standard deviation (p = 0.01), decrease of daily mean and minimum O(3) (p = 0.01), and of maximum of NO (p = 0.001), increase of daily O(3) standard deviation (p = 0.05). Daily decrement of standard deviation of temperature (p = 0.01) and increment ofWS anomalies and minima (p = 0.01) were also significant. Meteorological parameters and atmospheric pollutants might explain cluster hospitalization.

Present-day temperature standard deviation parameterization for Greenland

Present-day temperature standard deviation parameterization for Greenland

Modelling and adaptive control of small capacity chillers for HVAC applications

Abstract An adaptive controller for single and uneven tandem scroll compressor, packaged air-cooled water chillers is described. The designed controller allows to substantially increase the energy performance of the system, as well as to achieve excellent regulation performances in process applications. The controller parameters are adapted on the basis of estimates of the plant thermal load, that are computed by using a Kalman filter. An ad hoc approach is used to define a relay control logic, which is based on a numerical optimization procedure. To support controller design, a detailed simulation environment is developed and validated on an experimental facility. Performance of the algorithm is described with both simulation and experimental data. At low part load ratio values the proposed algorithm grants a 0.6–0.7 K improvement in the regulation performance in terms of supply water temperature standard deviation and mean supply water temperature deviation. The unit energy efficiency improvement with respect to supply water temperature control varies from 7.3% to 3.0% while the experimental seasonal energy efficiency rating improvement is 9.1%.

Comparison of objective descriptions of the thermocline

Temperature‐depth profiles, including the thermocline, are typically described or characterized by mixed layer depth, thermocline depth, and thermocline strength. Objective methods of estimating these parameters are compared with empirical determinations for 200 CTD profiles collected in the eastern and central tropical Pacific, the subtropical North Pacific, and the California Current. The objective methods are (1) maximum slope by difference, (2) maximum slope by regression, (3) four‐segment profile model, (4) inflection point, and (5) variable representative isotherm. Mixed layer depth is well estimated by the temperature criterion of (SST‐0.8°C) independent of the estimation of thermocline parameters. Thermocline depth and strength are well estimated by the variable representative isotherm method. However, thermocline strength measured as the slope of the temperature‐depth profile does not provide a good measure of stratification of the water column. Therefore, it is recommended that the thermocline strength estimate for a profile be supplemented by an estimate of the standard deviation of temperature in the near‐surface layer including the thermocline.

Potentials for radio occultation applications during inter-satellite calibration periods

EUMETSAT has launched the first in a series of three Metop satellites in October 2006. Each satellite has a nominal 5 year life time, covering 14 years in total. Successive satellites will be launched with about 0.5 year overlap into the same sun-synchronous polar orbit, allowing inter-satellite calibration. Focusing on the GRAS RO (radio occultation) instrument, we analyze two possible applications of this inter-satellite calibration period to assess: (1) the inherent RO precision by matching observations across the two satellites; (2) possible RO contributions to calibrate Earth-viewing sounders on-board the platforms by matching occultations with these sounders. Both applications are relevant for climate monitoring. An inherent precision assessment depends on the applied collocation criteria. We investigate the impact on bending angle, refractivity, temperature standard deviations by collocating GRAS/COSMIC and COSMIC/COSMIC. Even with close collocations, bending angle standard deviations are never found below 1%; in refractivity processing they are reduced by a factor of more than two. In temperature, they are never below 1 K. A 1DVar based impact assessment of these criteria on the temperature error shows an additional error of about 0.3 K when moving from matches within 100–300 km. Using ECMWF data, the atmospheric variability over the investigated collocations is assessed. With simulations we next analyze RO matches between 2 Metops with separation times of in-between 25 min and 50 min. Fairly relaxed spatial collocation criteria are required with these separation times to find strict matches, where the same GPS satellite is observed in the same viewing geometry. Such spatial collocations are unsuited to assess application (1); separation times of <6 min are required to collect enough matches. It is however possible to find more than 150 matches per day based on a criteria of ⩽300 km, ⩽3 h. For application (2), we find collocated sounder pixels for about 90% of the occultations for collocations within ⩽100 km, ⩽ 3 h, independent of whether the observations are made on the same or different platforms. Although this is reduced for close to nadir azimuth angles.

Real‐time MR thermometry for monitoring HIFU ablations of the liver

A high-resolution and high-speed pulse sequence is presented for monitoring high-intensity focused ultrasound ablations in the liver in the presence of motion. The sequence utilizes polynomial-order phase saturation bands to perform outer volume suppression, followed by spatial-spectral excitation and three readout segmented echo-planar imaging interleaves. Images are processed with referenceless thermometry to create temperature-rise images every frame. The sequence and reconstruction were implemented in RTHawk and used to image stationary and moving sonications in a polyacrylamide gel phantom (62.4 acoustic W, 50 sec, 550 kHz). Temperature-rise images were compared between moving and stationary experiments. Heating spots and corresponding temperature-rise plots matched very well. The stationary sonication had a temperature standard deviation of 0.15 degrees C compared to values of 0.28 degrees C and 0.43 degrees C measured for two manually moved sonications at different velocities. Moving the phantom (while not heating) with respect to the transducer did not cause false temperature rises, despite susceptibility changes. The system was tested on nonheated livers of five normal volunteers. The mean temperature rise was -0.05 degrees C, with a standard deviation of 1.48 degrees C. This standard deviation is acceptable for monitoring high-intensity focused ultrasound ablations, suggesting real-time imaging of moving high-intensity focused ultrasound sonications can be clinically possible.

Turbulence Intensity Parameters over a Very Complex Terrain

Detailed knowledge of turbulence structure is important for the understanding of atmospheric phenomena in the boundary layer, especially over complex terrain. In the present study, turbulence intensity parameters are analyzed for different conditions regarding stability, wind speed and wind direction over a mountainous region. The purpose of the analysis is to verify whether the observed parameters follow Monin–Obukhov similarity theory (MOST), despite the terrain heterogeneity. The dataset was collected during an experimental campaign at the Nova Roma do Sul site, in southern Brazil, with a micrometeorological tower located near a sharp slope, approximately 400 m high. The results show that the normalized standard deviations of the vertical velocity component as well as the normalized standard deviation of temperature follow Monin–Obukhov similarity for all stability regimes, regardless of the wind direction. However the normalized standard deviation of the horizontal components of the turbulent velocity obeys the similarity relationship only for a limited range of the stability parameters.

Land-Atmosphere Energy Transfer and Surface Boundary Layer Characteristics in the Rongbu Valley on the Northern Slope of Mt. Everest

The land-atmosphere interaction processes are unique at Mt. Everest as a result of high elevation. Based on turbulent data collected from April 2005 to March 2006 with the eddy covariance method at Quzong in the Rongbu Valley on the northern slope of Mt. Everest, land-atmosphere energy budget before and after the southwest monsoon onset and surface layer turbulent characteristics are studied for the first time. It is found that energy budget components (net radiation flux, sensible heat flux, latent heat flux, and soil heat flux) and surface heating field have strong diurnal and seasonal variations. In particular, under the influence of the southwest monsoon, the characteristics of surface parameters can be clearly identified. From pre-monsoon to monsoon season, the sensible heat flux decreases whereas the latent heat flux increases. The latent heat flux and Evaporative Fraction at Quzong are relatively high most of the year. Furthermore, the intensity of heating source in the wet season (from June to August) is much greater than that in the dry season (from October to December). The relationship between normalized standard deviation of wind speed and atmospheric stability, variations of normalized standard deviation of temperature, and humidity with atmospheric stability are analyzed using the Monin-Obukhov similarity theory. The result reveals that the normalized standard deviation of velocity components of the three-dimensional wind speed follows similarity relationships in the convective and near-neutral surface layer, but does not seem to be valid in stable surface layer. However, the normalized standard deviation of temperature and humidity does not obey Monin-Obukhov similarity theory in the entire interval of atmospheric stratifications.

Methods to Estimate Surface Fluxes of Momentum and Heat from Routine Weather Observations for Dispersion Applications under Stable Stratification

We examine the efficacy of two methods commonly used to estimate the vertical turbulent fluxes of momentum and sensible heat from routinely observed mean quantities in the surface layer under stable stratification. The single-level method uses mean wind speed and temperature measurements at a single height, whereas the two-level method uses mean wind speed measurements at a single height and mean temperature measurements at two heights. These methods are used in popular meteorological processors such as the U.S. Environmental Protection Agency approved AERMET and CALMET to generate inputs for dispersion simulations. We use data from a flux station of the U.K. Met Office at Cardington for comparison. It is found that the single-level method does not describe the flux variation in the weakly stable regime at all, because of its assumption that the temperature scale, i.e. the ratio of the kinematic sensible heat flux to the friction velocity, is constant, which is plausible only under strongly stable conditions. On the other hand, the two-level method provides a physically realistic variation of the fluxes with stability, but the required temperature measurements at two levels are usually not available on a routine basis. If measurements of the standard deviation of temperature are also available, in addition to the mean temperature at a single level, then they can be usefully employed in a third (single-level) method, with the consequence that the computed fluxes are very similar to those obtained from the two-level method. An improvement to the original single-level method is considered, and flux calculations under low wind conditions are also discussed.

A Simple Method of Estimating Scalar Fluxes Over Forests

A simple aerodynamic-variance method is proposed to fill gaps in continuous CO2 flux measurements in rainy conditions, when open-path analysers do not function. The method requires turbulent conditions (friction velocity greater than 0.1 ms–1), and uses measurements of mean wind speed, and standard deviations of temperature and CO2 concentration fluctuations to complement, and at times replace, eddy-covariance measurements of friction velocity, sensible heat flux and CO2 flux. Friction velocity is estimated from the mean wind speed with a flux-gradient relationship modified for the roughness sublayer. Since normalised standard deviations do not follow Monin-Obukhov similarity theory in the roughness sublayer, a simple classification scheme according to the scalar turbulence scale was used. This scheme is shown to produce sensible heat and CO2 flux estimates that are well correlated with the measured values.

Climate and geographic trends in hatch delay of the treehole mosquito, Aedes triseriatus Say (Diptera: Culicidae)

Eggs of Aedes triseriatus mosquitoes are stimulated to hatch when inundated with water, but only a small fraction of eggs from the same batch will hatch for any given stimulus. Similar hatching or germination patterns are observed in desert plants, copepods, rotifers, insects, and many other species. Bet hedging theory suggests that parents stagger offspring emergence into vulnerable life history stages in order to avoid catastrophic reproductive failures. For Ae. triseriatus, a treehole breeding mosquito, immediate hatching of an entire clutch leaves all of the parent's progeny vulnerable to extinction in the event of a severe drought. Natural selection has likely favored parents that pursued a bet hedging strategy where the risk of reproductive failure is distributed over time. Considering treehole mosquitoes, bet hedging theory could be used to predict that hatch delay would be positively correlated with the likelihood of drought. To test this prediction, we collected Ae. triseriatus from habitats that varied widely in mean annual precipitation and exposed them to several hatch stimuli in the laboratory. Here we report that, as predicted, Ae. triseriatus eggs from high precipitation regions showed less hatch delay than areas of low precipitation. This strategy probably allows Ae. triseriatus to cope with the wide variety of climatic conditions that it faces in its extensive geographical range.

The Influence of Local Stability on Heat and Momentum Transfer within Open Canopies

Eddy-covariance data have been analyzed to investigate the influence of local stability on heat transfer within open canopies. The flux–gradient relationship for heat is derived from the temperature variance equation, and the stability dependence of the flux–gradient relationship is examined and discussed. The results indicate that the strong stability dependence of the nondimensional standard deviation of temperature, and the small contributions of turbulent transport to the temperature variance, lead to a strong stability dependence of the nondimensional temperature gradient within open canopies. Quadrant analysis and hole size analysis were performed for momentum and heat fluxes in the subcanopy, and the results indicate that the contribution of each quadrant to the total flux depends on both the local stability and canopy depth. The intermittency of the turbulent flux does not show a clear dependence on local stability. As the contribution of ejections to the heat flux increases, the vertical flux of the temperature variance changes sign from negative to positive, leading to small temperature variance transport in unstable conditions. Multi-resolution analysis indicates that heat and momentum are transported with different dominant time scales in very unstable conditions, suggesting a different role of local buoyancy in heat and momentum transfer.

Characterization of the Martian Convective Boundary Layer

Abstract The authors have carried out an extensive characterization of the Martian mixed layer formed under convective conditions. The values of the mixed layer height, convective velocity scale, convective temperature scale, mean temperature standard deviation, mean horizontal and vertical velocity standard deviations, and mean turbulent viscous dissipation rate have been obtained during the strongest convective hours for the mixed layer. In addition, the existing database of the surface layer has been improved by recalculating some parameters (e.g., Monin–Obukhov length, friction velocity, or scale temperature) that had already been obtained in previous papers by other means and also by calculating new ones, such as the standard deviation of the vertical wind speed velocity, the turbulent viscous dissipation rate, and eddy transfer coefficients for momentum and heat. The Earth counterparts of all these magnitudes are also shown. In this paper, a comprehensive database concerning the whole convective planetary boundary layer on Mars is displayed, and a detailed terrestrial comparison is established. The inputs of this work are hourly in situ temperature, hourly in situ horizontal wind speed, and hourly simulated ground temperature for specific selected Sols of the Viking and Pathfinder landers. These data correspond to typical low and midlatitude northern summertime conditions, with weak prevailing winds. To handle this set of data, surface layer and mixed layer similarity theory have been used at the strongest convective hours. In addition, the inclusion of a parameterization of a molecular sublayer and prescribed values of the surface roughness has been considered.

Relative intensities of middle atmosphere waves

Climatologies of gravity waves, quasi‐stationary planetary waves, and tides are compared in the upper stratosphere, mesosphere, and lower thermosphere. Temperature standard deviations from zonal means are used as proxies for wave activity. The sum of the waves is compared to directly measured total temperature fluctuations. The resulting difference is used as a proxy for traveling planetary waves. A preliminary climatology for these waves is proposed. A ranking of the four wave types in terms of their impact on the total wave state of the atmosphere is achieved, which is dependent on altitude and latitude. At extratropical latitudes, gravity waves mostly play a major role. Traveling planetary waves are found to play a secondary role. Quasi‐stationary planetary waves and tides yield a lesser contribution there. Vertical profiles of total temperature fluctuations show a sharp vertical gradient change (“kink” or “bend”) in the mesosphere. This is interpreted in terms of a change of wave damping, and the concept of a “wave turbopause” is suggested. The altitude of this wave turbopause is found to be mostly determined by the relative intensities of gravity waves and planetary waves. The turbopause is further analyzed, including earlier mass spectrometer data. It is found that the wave turbopause and the mass spectrometer turbopause occur rather close together. The turbopause forms a layer about 8 km thick, and the data suggest an additional 3 km mixing layer on top.

Adjoint-Based Sensitivity Analysis and Error Correction Methods Applied to Solid Oxide Fuel Cells

Sensitivity analysis and design optimization of solid oxide fuel cells are presented. Multispecies diffusion, low speed convection, and chemical kinetics are included in a two-dimensional numerical model, and sensitivity derivatives are computed using both discrete adjoint method and direct differentiation. The implementation of the discrete adjoint method is validated by comparing sensitivity derivatives obtained using the adjoint with results obtained using direct differentiation and finite-difference methods. For optimization, cost functions describing hydrogen concentration along the anode-electrolyte interface, hydrogen concentration at the channel outlet, and standard deviation of temperature inside the anode are considered. Material properties of the anode, operating conditions, and a shape parameter are selected as design variables. The development of an initial design environment to automate the flowfield solution, sensitivity computation, optimization, and mesh movement is also described. Finally, an adjoint-based error correction method is implemented and demonstrated to provide accurate estimations for a desired objective function on a fine mesh by combining information obtained from analysis and adjoint solutions on a coarser one.

Linear mixing in thermal infrared temperature retrieval

Virtually all remotely sensed thermal infrared (IR) pixels are, to some degree, mixtures of different materials or temperatures: real pixels are rarely thermally homogeneous. As sensors improve and spectral thermal IR remote sensing becomes more quantitative, the concept of homogeneous pixels becomes inadequate. Quantitative thermal IR remote sensors measure radiance. Planck's Law defines a relationship between temperature and radiance that is more complex than linear proportionality and is strongly wavelength‐dependent. As a result, the area‐averaged temperature of a pixel is not the same as the temperature derived from the radiance averaged over the pixel footprint, even for blackbodies. This paper uses simple linear mixing of pixel elements (subpixels) to examine the impacts of pixel mixtures on temperature retrieval and ground leaving radiance. The results show that for a single material with one temperature distribution and with a subpixel temperature standard deviation of 6 K (daytime images), the effects of subpixel temperature variability are small but can exceed 0.5 K in the 3–5 µm band and about a third of that in the 8–12 µm band. For pixels with a 50 : 50 mixture of materials (two temperature distributions with different means) the impact of subpixel radiance variability on temperature retrieval can exceed 6 K in the 3–5 µm band and 2 K in the 8–12 µm band. Sub‐pixel temperatures determined from Gaussian distributions and also from high‐resolution thermal images are used as inputs to our linear mixing model. Model results are compared directly to these broadband thermal images of plowed soil and senesced barley. Finally, a theoretical framework for quantifying the effect of non‐homogeneous temperature distributions for the case of a binary combination of mixed pixels is derived, with results shown to be valid for the range of standard deviations and temperature differences examined herein.

Design of Calibrators for Profile Extrusion – Optimizing Multi-step Systems

Abstract A computer code, that couples numerical modelling and optimization routines, is described and used to automatically optimize the performance of a multi-step calibration stage of a plastic profile extrusion line. The objective of the optimization process is to minimize two conflicting criteria: final plastic profile average temperature and corresponding distribution standard deviation, both computed at the end of the calibration/cooling stage. The optimization routine uses Multi-Objective Evolutionary Algorithms (MOEA). Having in mind the well-known difficulties in characterizing the interface heat transfer coefficient, the system optimization was performed using different constant values for this parameter.