Amplitude Of Surface Temperature Research Articles

A simple method for the estimation of thermal inertia

A simple method for estimating thermal inertia using daily amplitude of surface soil heat flux and temperature is proposed. Based on an analytical solution of the diffusion equation where the soil temperature is idealized as a sinusoidal function, the thermal inertia is expressed as a proportional coefficient in a linear equation relating the amplitudes of surface soil (ground) heat flux and temperature. Tests of the proposed method demonstrate that this simple method is potentially useful in the Earth and extra‐terrestrial remote sensing.

Effects of transient diesel engine operation on its cyclic heat transfer: an experimental assessment

This paper presents results from the analysis of experimental data with the aim of investigating the cyclic, instantaneous heat transfer phenomena occurring in both the cylinder head and exhaust manifold wall surfaces of a direct injection, air-cooled diesel engine, operating under transient events (long-term), viz. during a sudden change in engine speed and/or load, rather than the usual steady state. The experimental installation allowed both for long- and short-term signal types to be recorded on a common time reference base during the transient event. Processing of experimental data was accomplished using a modified version of one-dimensional heat conduction theory with Fourier analysis, capable of catering for the special characteristics of transient engine operation. Based on this model, the evolution of local surface heat flux during a transient event was calculated. Two engine transient events are examined, which present a key difference in the way the load and speed changes are imposed on each one of them. It is revealed that in the case of a ‘ramp’ transient the amplitude of wall surface temperature and heat flux variation in the combustion chamber during the first 20 engine cycles was increased by almost three times more than the corresponding ones during steady state operation. At the same time, temporal gradients of cylinder pressure and wall surface temperature are also sharply increased in the combustion chamber and exhaust manifold surfaces. The variation of cylinder pressure, surface temperature, and heat flux is altered significantly during the transient event, with their peak values either advanced or retarded compared with those for the corresponding steady state operation. The previous observations are moderated or even vanished in the case of a ‘slow pace’ transient variation, revealing the significant influence of engine speed and load triggered by the external command, on the response of heat transfer variables. During a ramp transient, the amplitude of wall temperature swing is increased significantly even at a depth of a few millimetres below the surface of the combustion chamber, thereby influencing the dissipation of heat towards its external layers. Under these circumstances, the depth of penetration for temperature oscillations inside the metal volume is also significantly increased.

Spectral Behaviour of a Coupled Land-Surface and Boundary-Layer System

The temporal spectral response of a coupled land-atmosphere system to daily forcing of net radiation at the land surface is investigated using the analytic approach. The original definition of the problem dates back to an early study by Lettau. The present study builds on the problem and introduces some important additions, with a focus on the propagation of heat flux and temperature waves in both the soil and the atmospheric boundary layer. The study highlights the dependence of the complex amplitude of surface temperature and heat fluxes on the different land-surface parameters, such as friction velocity, evaporative fraction, aerodynamic resistance and vegetation height. Finally, the dependency of surface state variables to the frequency of the forcing is analyzed.

Thermal diffusivity measurements of thin plates and filaments using lock-in thermography

Photothermal radiometry has been widely used to measure the thermal diffusivity of bulk materials. In the case of thin plates and filaments, a one-dimensional heat propagation model including heat losses has been developed, predicting that the thermal diffusivity can be obtained by recording both the surface temperature amplitude and phase profile slopes ("slope method"). However, this method has given highly overestimated values of the thermal diffusivity of poor-conducting films and filaments. In this paper we analyze the effect of the experimental factors affecting the thermal diffusivity measurements of thin plates and filaments using infrared thermography, in order to establish the experimental conditions needed to obtain accurate and reliable values of the diffusivity of any kind of material using the slope method. We present the calculations of the surface temperature of thin isotropic and anisotropic plates heated by a modulated and tightly focused laser beam, showing that the slope method is also valid for this kind of pointlike heating. Special attention is paid to the effect of surface heat losses (convective and radiative) on the diffusivity measurements of small-dimension and poor-conducting materials. Lock-in thermography measurements performed in the best experimental conditions on a wide set of samples of different thermal properties (thin isotropic and anisotropic plates and filaments) confirm the validity of the slope method to measure accurately the thermal diffusivity of samples of these shapes.

Numerical analysis for critical thickness of crushed rock revetment layer on Qinghai–Tibet Railway

Abstract Under the warm and ice-rich nature of permafrost and the scenarios of climate warming on the Qinghai–Tibet Plateau, the construction of Qinghai–Tibet Railway has to utilize new techniques by cooling down the ground temperature. The non-dimensional governing equations for natural convection in variable permeability porous media are derived. Onset and development of winter-time natural convection in the crushed rock revetment of Qinghai–Tibet Railway are investigated by an airflow function. Numerical results indicate that the natural convection pattern occurring within the crushed rock revetment will be unicellular, thus forming the chimney effect to cool down the roadbed during winter months. In order to evaluate the cooling effectiveness of winter-time natural convection in the crushed rock revetment embankment, the overall Nusselt number and relevant Nusselt percentage representing heat transfer through unit length at the embankment base were defined. The dependences of the overall Nusselt number and relevant Nusselt percentage on the thickness of crushed rock revetment layer and the amplitude of harmonic surface temperature are analyzed using a numerical representation of the non-dimensional governing equations for convection. The approach to evaluation of critical thicknesses of crushed rock revetment in the railway embankment was developed on the basis of the dependence of the overall Nusselt percentage on the thickness of crushed rock revetment and the amplitude of harmonic surface temperature. Validity of evaluating thicknesses of crushed rock revetment filled in the embankment was demonstrated both numerically and experimentally. Thus, this evaluation approach is available for the construction of Qinghai–Tibet Railway.

A moving boundary problem derived from heat and water transfer processes in frozen and thawed soils and its numerical simulation

The seasonal change in depths of the frozen and thawed soils within their active layer is reduced to a moving boundary problem, which describes the dynamics of the total ice content using an independent mass balance equation and treats the soil frost/thaw depths as moving (sharp) interfaces governed by some Stefan-type moving boundary conditions, and hence simultaneously describes the liquid water and solid ice states as well as the positions of the frost/thaw depths in soil. An adaptive mesh method for the moving boundary problem is adopted to solve the relevant equations and to determine frost/thaw depths, water content and temperature distribution. A series of sensitivity experiments by the numerical model under the periodic sinusoidal upper boundary condition for temperature are conducted to validate the model, and to investigate the effects of the model soil thickness, ground surface temperature, annual amplitude of ground surface temperature and thermal conductivity on frost/thaw depths and soil temperature. The simulated frost/thaw depths by the model with a periodical change of the upper boundary condition have the same period as that of the upper boundary condition, which shows that it can simulate the frost/thaw depths reasonably for a periodical forcing.

An analysis of phase change material as thermal mass

Temperature fluctuations within a building can be attenuated by thermal mass. Adding phase change material (PCM) to thermal mass increases the effective heat capacity during the phase transition. This can anchor the temperature of the mass in a narrow band around the melting point of the PCM, further reducing the temperature swings perceived by occupants of the room. A simple dimensionless model for thermal mass forced by a sinusoidally varying air temperature is developed to calculate the performance of the PCM. The mass temperature satisfies the heat equation, with a temperature-dependent thermal diffusivity, and is solved numerically. For a given PCM, the energy stored and returned to the room, the surface temperature amplitude and the penetration depth of heat pulses into a hypothetical semi-infinite mass can all be calculated as a function of a single dimensionless parameter. For optimal performance, the latent heat of the PCM should be as large as possible, the melting temperature range should be narrow and the thickness of the mass should exceed the penetration depth. The PCM wallboard is shown to be potentially as effective as conventional concrete, so lightweight buildings could enjoy the benefits of thermal inertia commonly associated with heavyweight structures.

Development of an Ecologic Marine Classification in the New Zealand Region

We describe here the development of an ecosystem classification designed to underpin the conservation management of marine environments in the New Zealand region. The classification was defined using multivariate classification using explicit environmental layers chosen for their role in driving spatial variation in biologic patterns: depth, mean annual solar radiation, winter sea surface temperature, annual amplitude of sea surface temperature, spatial gradient of sea surface temperature, summer sea surface temperature anomaly, mean wave-induced orbital velocity at the seabed, tidal current velocity, and seabed slope. All variables were derived as gridded data layers at a resolution of 1 km. Variables were selected by assessing their degree of correlation with biologic distributions using separate data sets for demersal fish, benthic invertebrates, and chlorophyll-a. We developed a tuning procedure based on the Mantel test to refine the classification's discrimination of variation in biologic character. This was achieved by increasing the weighting of variables that play a dominant role and/or by transforming variables where this increased their correlation with biologic differences. We assessed the classification's ability to discriminate biologic variation using analysis of similarity. This indicated that the discrimination of biologic differences generally increased with increasing classification detail and varied for different taxonomic groups. Advantages of using a numeric approach compared with geographic-based (regionalisation) approaches include better representation of spatial patterns of variation and the ability to apply the classification at widely varying levels of detail. We expect this classification to provide a useful framework for a range of management applications, including providing frameworks for environmental monitoring and reporting and identifying representative areas for conservation.

Lake surface water temperature retrieval using advanced very high resolution radiometer and Moderate Resolution Imaging Spectroradiometer data: Validation and feasibility study

In this study we prove the feasibility of the advanced very high resolution radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer sea surface temperature algorithms to derive operational lake surface water temperature (LSWT). A validation study covering 2 years was done using data from the AVHRR on NOAA 12, 15, 16, and 17, the MODIS on TERRA, and AQUA and with different method‐ingested in situ data from different sized lakes. Best results were found for NOAA 16 nighttime data at Lake Geneva (bias of 0.18 K and standard deviation of 0.73 K) and TERRA nighttime data at Lake Constance (satellite‐buoy bias of −0.08 K and standard deviation of 0.92 K). For all sensor families an overall scatter ranging from 0.9 to 1.6 K was found. Bias of MODIS is larger, −1.73 to 1.9 K, than the one of the AVHRR (−0.28 to 1.5 K). The current orbital configuration of the platforms used revealed the diurnal evolution of the lake surface temperature amplitude from space. The damped mixing found for a typical calm and clear‐sky regime is different from open ocean conditions. As the main error source, we found undetected cloudy pixel. Furthermore, the physical difference between skin and bulk temperature, especially its relation to the diurnal thermocline, solar insolation, and wind stress contributes to the bias and scatter within the match‐up data set. The data sets have been validated to allow further application for LSWT climatology and assimilation into numerical weather prediction models.

A diagnostic model of the diurnal cycle of sea surface temperature for use in coupled ocean‐atmosphere models

On the basis of a method of estimating the diurnal amplitude of sea surface temperature (SST) as a function of the diurnal integrals of surface heat and momentum fluxes, a parameterization scheme of the diurnal cycle of SST is implemented in a one‐dimensional ocean mixed‐layer model. Many coupled ocean‐atmosphere models using bulk mixed‐layer schemes underestimate the diurnal cycle in sea surface temperature by up to 2°C. This discrepancy is caused by coarse vertical resolution in the upper grid boxes of the ocean components. A simple solution is suggested by adding one extra transient level: a variable‐depth diurnal sublayer within the top model level which accommodates the diurnal buoyancy cycle. A one‐dimensional mixed‐layer model with 10‐m resolution and with sublayer simulates diurnal SSTs close to those observed from the Tropical Ocean Global Atmosphere/Coupled Ocean Atmosphere Response Experiment (TOGA/COARE) with typical errors of about 0.1°C. The impact of improved SSTs on surface heat fluxes is also shown by coupling the one‐dimensional mixed‐layer model with sublayer to an atmospheric boundary layer model.

Experimental investigation of thermal and moisture behaviors of wet and dry soils with buried capillary heating system

An experimental study of thermal and moisture behaviors of dry and wet soils heated by buried capillary plaits was done. This study was carried out on a prototype similar to an agricultural tunnel greenhouse. The experimental procedure consisted on three different measuring phases distinguished by three different operational conditions of the capillary plaits: heating at 70 °C, heating at 40 °C and without heating in summer. During an experimental run, quantities measured are soil temperature, soil water content at various depths, soil surface heat flux, solar radiation under the plastic cover, internal relative humidity, internal and external air temperature. In unsaturated moist soils, the transport of heat is complicated by the fact that heat and mass transfer is a coupled process. During the daily soil temperature variation, it was found that the surface temperature amplitude was higher in wet soil than in dry soil. The water content increased during daytime and decreased during nighttime. The diurnal variation amplitude of water content was higher without underground heating and decreased with the buried heat source temperature.

Spatial and temporal variations of model‐derived diurnal amplitude of sea surface temperature in the western Pacific Ocean

The diurnal amplitude of sea surface temperature (SST) at 1‐m depth is estimated with a simple empirical model in the region of 80°E–160°W, 60°S–60°N covering the western Pacific Ocean using 4 years of satellite‐derived wind speed, solar radiation, and latent heat flux data. The advantage of this indirect method is that the diurnal amplitude of SST (ΔSST) can be obtained even in cloudy areas. ΔSST is large in the tropics through the year. Summer ΔSST in the middle and high latitudes of the Northern Hemisphere, especially around Japan, is larger than that of the Southern Hemisphere. However, ΔSST in the Kuroshio and its extension regions is smaller compared with that in its surrounding ones because of higher wind speed. In the Bay of Bengal, the South China Sea, and the Timor Sea, ΔSST becomes largest in spring, when the surface wind becomes weak in the transition of the monsoon. The period of about 35–50 days is clearly seen in the temporal variation of ΔSST in the tropics. This reflects the Madden‐Julian oscillation. Furthermore, there are some differences in ΔSST between El Niño and La Niña periods. The authors then investigate how clouds affect the detection of ΔSST. If sampling is limited to clear areas only, the areas of strong solar radiation and weak wind are selectively picked up, and the probability that larger ΔSST is sampled increases. The mean of the ΔSST sampled from clear areas only is greater by 0.2–0.3 K compared with the actual mean.

Surface energy balance characteristics of a heterogeneous urban ballast facet

Surface energy balance measurements were conducted during a study period from June to September 2002 at a goods station in Osnabruck, Germany. The inner-urban facet with a surface area of 0.5 km 2 was predominantly covered by ballast. Turbulent latent and sensible heat fluxes were estimated by a modified Bowen ratio method; the ground heat flux was calculated from temperature gradients and a laboratory derived thermal conductivity. The thermal behaviour of the ballast facet in comparison to other urban surfaces is somewhat 'two-sided'. Due to its thermal properties it behaves similarly to urban surfaces during the day, with high surface temperatures and large near- surface temperature amplitudes. About one-third of the incoming energy is converted into the turbu- lent sensible heat flux and 20% is converted into the ground heat flux. The latent heat flux at the site is of minor importance (16%). During the night, however, the thermal behaviour is more comparable to a 'rural-like' surface than to an urban facet. The ballast surface cools significantly and the sensible heat flux is directed towards the surface. Due to the heterogeneity of the study site the energy bal- ance shows a closure gap of around 30%. Reasons for the energy balance non-closure are discussed.

The influence of soil moisture transfer on building heat loss via the ground

In this paper, the influence of soil moisture transfer on building heat loss via the ground is investigated by comparing fully coupled simulations with linear thermal simulations. The observed influences of coupling are (1) the larger amplitude of surface temperature, (2) the variation of thermal conductivity with moisture content, and (3) the advection of sensible heat by liquid transfer. In a parameter study, it is shown that these conclusions hold for a variety of climates, soils and foundation constructions. However, given the current accuracy level of standard methods, the integration of coupling effects in these calculation methods cannot be defended.

Wind-induced upwelling in the western equatorial Pacific Ocean observed by multi-satellite sensors

R/V MIRAI (MR01-K05 Leg3) of Japan Marine Science and Technology Center (JAMSTEC) was stationed at the point of 2° North and 138° East in the western equatorial Pacific Ocean from November 9 to December 9, 2001. During this air–sea interaction research cruise SeaWiFS and NOAA/AVHRR local area coverage (LAC) scenes were received by the station onboard R/V MIRAI and the products derived from these satellites are verified against oceanographic observations including the parameter of sea surface temperature, salinity, chlorophyll- a and current velocity profile to the depth of 300 m. Level 3 wind vector products derived from QuickSCAT onboard SeaWinds are also collected and validated against in situ wind vectors. The diurnal change of amplitude of sea surface temperature decreases from 1.5° to 0° after the week-long prevailing northwest monsoon wind with the maximum gust more than 20 m/s while the observed surface salinity and chlorophyll- a concentration increase from 34.1 to 34.37 and from 0.05 to 0.14 mg/m 3, respectively. The increase of chlorophyll- a and the decrease of sea surface temperature in this region are shown in the multi-date SeaWiFS chlorophyll- a concentration products and multi-channel sea surface temperature (MCSST) products from NOAA/AVHRR. Wind vector patterns before and after the gust more than 20 m/s are also observed by QuickSCAT. During the period of the week-long northwest monsoon wind the current velocity of upper 70 m reaches about 70 cm/s in the southeastward direction while the current velocity at the depth from 80 to 120 m indicates 50 cm/s in the northwestward direction. The current of upper 70 m corresponds to the northwest monsoon current (NMC) and the intrusion of NMC enhanced by the strong northwest monsoon winds (westerly wind bursts) causes a reversal in the sub-surface current (New Guinea coastal undercurrent, NGCUC) which creates a temporal upwelling in this region.

Periodic conduction in materials with non-Fourier behaviour

The paper investigates the effects of non-Fourier characteristics of the material on oscillating thermal fields. A general solution in terms of temperature Fourier transform is obtained for an 1-D slab with convective boundary conditions. A transfer matrix of the slab is evaluated and it is shown that its analysis gives information about the non-Fourier behaviour of the material. Periodic conduction is analysed for both harmonic and nonharmonic boundary conditions, and the effect of surface convection is pointed out through the evaluation of its influence on surface temperature phase lag and amplitude. The possibility of evaluating relaxation time from phase lag measurements is pointed out together with the limits imposed by the surface convection. A similar technique is shown to be theoretically applicable to periodic nonharmonic boundary conditions through the evaluation of the temperature-heat flux cross-correlation.

Validation of Daily Amplitude of Sea Surface Temperature Evaluated with a Parametric Model Using Satellite Data

The authors have verified a regression model for the evaluation of the daily amplitude of sea surface temperature (ΔSST) proposed by Kawai and Kawamura (2002). The authors investigated the accuracy of satellite data used for the evaluation and showed that ΔSST error caused by satellite data error is less than ±0.7 K. The evaluated ΔSSTs were compared with in situ values. Its root-mean-square error is about 0.3 K or less, except for a coastal region, and it has a bias of more than +0.1 K in the tropics. This bias can be removed by considering latent heat flux.

Indian Ocean Intraseasonal Variability in an Ocean General Circulation Model

Abstract The impact of atmospheric intraseasonal variability on the tropical Indian Ocean is examined with an ocean general circulation model (OGCM). The model is forced by observation-based wind stresses and surface heat fluxes from an atmospheric boundary layer model. Composites of 26 well-defined boreal spring and summer intraseasonal events from 1985 to 1994 are used to explore surface and subsurface impacts of intraseasonal oscillations in the ocean. The phase and amplitude of simulated intraseasonal sea surface temperature (SST) variations agree well with observations. The net surface heat flux dominates the composite mixed layer heat budget on intraseasonal timescales, while entrainment through the base of the mixed layer contributes locally. Horizontal advection is of secondary importance in the composite heat balance. However, inspection of individual events suggests that in individual intraseasonal events different processes may control their dynamics. A characteristic feature of equatorial intr...

Modeling seasonal phosphate export and resupply in the Subantarctic and Polar Frontal zones in the Australian sector of the Southern Ocean

We developed and applied a one‐dimensional (z) biophysical model to the Subantarctic Zone (SAZ) and the Polar Frontal Zone (PFZ) to simulate seasonal phosphate export production and resupply. The physical component of our model was capable of reproducing the observed seasonal amplitude of sea surface temperature and mixed layer depth. In the biological component of the model we used incident light, mixed layer depth, phosphate availability, and estimates of phytoplankton biomass from the Sea‐viewing Wide Field‐of‐view Sensor to determine production and tuned the model to reproduce the observed seasonal cycle of phosphate. We carried out a series of sensitivity studies, taking into account uncertainties in both physical fields and biological formulations (including potential influence of iron limitation), which led to several robust conclusions (as represented by the ranges below). The major growing season contributed 66–76% of the annual export production in both regions. The simulated annual export production was significantly higher in the PFZ (68–83 mmol P m−2) than in the SAZ (52–61 mmol P m−2) despite the PFZ's having lower seasonal nutrient depletion. The higher export production in the PFZ was due to its greater resupply of phosphate to the upper ocean during the September to March period (27–37 mmol P m−2) relative to that in the SAZ (8–15 mmol P m−2). Hence seasonal nutrient depletion was a better estimate of seasonal export production in the SAZ, as demonstrated by its higher ratio of seasonal depletion/export (64–78%) relative to that in the PFZ (34–47%). In the SAZ, vertical mixing was the dominant mechanism for supplying phosphate to the euphotic zone, whereas in the PFZ, vertical mixing supplied only 37% of the phosphate to the euphotic zone and horizontal transport supplied the remaining 63%.

Impacts of Diurnal Cycle of SST on the Intraseasonal Variation of Surface Heat Flux over the Western Pacific Warm Pool

Based on the method of estimating the diurnal amplitude of sea surface temperature (SST) as a function of daily averaged wind speed, precipitation and peak surface radiation, a parameterization scheme of diurnal cycle of SST is developed in the present study, Integrations to National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3), separately forced by observed weekly SSTs with and without diurnal cycle of SST, are compared. Surface observation obtained from the Improved Meteorology (IMET) buoy during TOGA COARE Intensive Observation Period is applied to verify the SST parameterization, as well as a validation to the results from the CCM3 simulation. It is shown that the superposition of diurnal cycle of SST to the forced weekly SST makes a more realistic representation of the surface structure of intraseasonal oscillation over the western Pacific warm pool.