Vertical Heat Transport Research Articles

A model study of the seasonal cycle of the Arabian Sea surface temperature

The Annual variation of the SST along a zonal strip from the coast of Somalia to the southwest coast of India was simulated using available data (monthly-mean heat and momentum fluxes across the air-sea interface, surface advective field, etc.) as input to a Kraus-Turner mixed-layer model. Three cases were examined. In the first, influence of surface fluxes alone was considered. The second included the effects of surface fluxes and vertical advection. Then, effect of horizontal advection was added. The model forced with the surface heat and momentum fluxes alone simulated reasonably well the SST variability throughout the year except during the May-August (southwest monsoon) cooling phase. The model was found to be inadequate to handle the coastal areas during this phase. Over the open-sea regime the performance of the model was better; and, it improved when the influence of advection was included. The important contribution of the horizontal advection during June-August was to remove most of the heat gained at the surface during the course of a year. Though downwelling in the open-sea had little influence on the SST, it had noticeable impact on the vertical heat transport. The numerical experiments suggest that the Kraus-Turner thermodynamics alone dominate the Arabian SST variability throughout the year except during the southwest monsoon, when dynamics too playa significant role.

Hydrographic observations from the Weddell Sea during the Norwegian Antarctic Research Expedition 1976/77

CTD observations from the southern Weddell Sea in 1977 show that Ice Shelf Water originating under the floating Filchner Ice Shelf overtlows at the sill of the Filchner Depression and can be identified on the continental slope at more than 2000m depth. Intrusions of Weddell Deep Water upon the shelf are especially noticeable in the region of dense shelf water outflow and are possibly driven by the outflow. Anomalous low core temperature of Weddell Deep Water is probably related to winter convection in the Weddell Polynya. Anomalous CTD stations at the periphery of the 1976 winter polynya region indicate that deep convection phenomena, as reported by Gordon (1978), are perhaps quite common. The observations indicate that double diffusive convection is important for vertical heat transport in the central Weddell Sea.

Fine‐structure variability observed in CTD measurements from the central equatorial Pacific

Conductivity, temperature, and depth data from the 15 quasi‐monthly cruises of the Hawaii‐Tahiti Shuttle Experiment are used to document fine‐structure variability in the upper 400 m of the central equatorial Pacific. The analysis reveals the existence of anomalously strong temperature and density variations on 0(1–10 m) vertical scales concentrated in the high mean shear zones of the equatorial current system and in the thermostad. These are regions where microscale measurements also indicate intense turbulent activity. The implication of this spatial correspondence between large‐, fine‐, and microscale signals is that there may be a cascade of energy from the largest to the smallest scales of variability that is mediated by fine‐structure processes. The highly structured fine‐scale signal suggests that the cascade would be most pronounced and persistent on certain density surfaces that lie within the regions of highest mean shear. Other processes, such as wind stirring, air‐sea buoyancy exchange, and intrusions, also contribute to the generation of fine‐structure variability and mixing at equatorial latitudes. There is evidence, for example, that intrusions across the sharp equatorial salinity front in the upper 150–200 m account for 10%–20% of the fine‐structure temperature variance and more than 50% of the fine‐structure salinity variance. The dominant vertical scale of these intrusions appears to be ≲10 m and the cross‐frontal scale < 100 km. A simple model calculation of cross‐frontal mixing indicates that they are important in transferring heat and salt laterally across the front. Intrusions in the vicinity of the Equatorial Undercurrent core may support salt fingering; hence they may contribute to vertical transports of salt and heat in a region where turbulent mixing is weak.

Characteristics of turbulent structures in the unstable atmospheric surface layer

An atmospheric surface-layer (ASL) experiment conducted at a meteorological site in the Oostelijk-Flevoland polder of the Netherlands is described. Turbulent fluctuations of wind velocity, air temperature and static pressure were measured, using three 10 m towers. Simultaneous turbulent signals at several heights on the towers were used to investigate the properties of the turbulent structures which contribute most significantly to the turbulent vertical transports in the unstable ASL. These turbulent structures produce between 30 and 50% of the mean turbulent vertical transport of horizontal alongwind momentum and they contribute to between 40 and 50% of the mean turbulent vertical heat transport; in both cases this occurs during 15 to 20% of the total observation time. The translation speed of the turbulent structures equals the wind speed averaged over the depth of the ASL, which scales on the surface friction velocity. The inclination angle of the temperature interface at the upstream edge of the turbulent structures to the surface is significantly smaller than that of the internal shear layer, which is associated with the temperature interface. The turbulent structures in the unstable ASL are determined by a large-scale temperature field: Convective motions, which encompass the whole depth of the planetary boundary layer (PBL), penetrate into the ASL. The curvature of the vertical profile of mean horizontal alongwind velocity forces the alignment of the convective cells in the flow direction (Kuettner, 1971), which have an average length of several hundreds of metres and an average width of a few tens of metres. This mechanism leads to the formation of turbulent structures, which extend throughout the depth of the ASL.

Hydrographic observations from the Weddell Sea during the Norwegian Antarctic Research Expedition 1976/77

CTD observations from the southern Weddell Sea in 1977 show that Ice Shelf Water originating under the floating Filchner Ice Shelf overtlows at the sill of the Filchner Depression and can be identified on the continental slope at more than 2000m depth. Intrusions of Weddell Deep Water upon the shelf are especially noticeable in the region of dense shelf water outflow and are possibly driven by the outflow. Anomalous low core temperature of Weddell Deep Water is probably related to winter convection in the Weddell Polynya. Anomalous CTD stations at the periphery of the 1976 winter polynya region indicate that deep convection phenomena, as reported by Gordon (1978), are perhaps quite common. The observations indicate that double diffusive convection is important for vertical heat transport in the central Weddell Sea.

A two‐dimensional model of the nightside ionosphere of Venus: Ion energetics

The energetics of the nightside ionosphere of Venus are still not well understood. Rather large ion temperatures have been observed on the nightside. We have constructed a two‐dimensional theoretical model of the energetics of the nightside ionosphere which takes into account the effects of horizontal and vertical bulk transport of heat. We demonstrate that the observed maintenance of the ion temperature can be explained in terms of these transport terms for solar zenith angles less than 150°. Simple heat transport cannot explain the observed high temperatures for angles greater than 150°.

Dynamical Heat-Flux Feedbacks and Global Climate Stability

In the face of the faint young sun-climate paradox, the plausible effects of dynamical heat-flux feedbacks on global stability were examined using a coupled high- and low-latitude radiative-dynamical model. The global stability is found to depend very strongly on the vertical heat transport, which is also closely coupled to the meridional heat transport. This coupling and the associated dynamical heat-flux feedbacks, treated within the framework of the radiative-dynamical model, was found to produce a fairly strong negative feedback. Our results indicate that the dynamical heat-flux feedbacks inherent in the climate system may potentially enhance the global stability.

Dynamical Heat-Flux Feedbacks and Global Climate Stability

In the face of the faint young sun-climate paradox, the plausible effects of dynamical heat-flux feedbacks on global stability were examined using a coupled high- and low-latitude radiative-dynamical model. The global stability is found to depend very strongly on the vertical heat transport, which is also closely coupled to the meridional heat transport. This coupling and the associated dynamical heat-flux feedbacks, treated within the framework of the radiative-dynamical model, was found to produce a fairly strong negative feedback. Our results indicate that the dynamical heat-flux feedbacks inherent in the climate system may potentially enhance the global stability.

The Measurement of Vertical Transports of Sensible Heat within and above a Sorghum Canopy

The observations of sensible heat flux were made at the 3 heights (260cm, 160cm, 100cm) in the sorghum field with a mean plant height of 160cm in August, 1982. The fluctuations of air temperature were measured at the 5 heights (260cm, 160cm, 100cm, 65cm, 20cm). The results are summarized as follows.1) The fluxes of sensible heat in the daytime were upward above and within plant canopies. The sensible heat flux above plant canopies were provided about 60% of flux from the upper layer between 160cm and 100 cm and about 40% from the layer below 100cm.2) The non-dimensional standard deviations (σT/|T*|) of air temperature were maximum at the top of the plant canopies, where T*=wT/u*, w and T are fluctuations of vertical velocity and temperature, and u* the friction velocity. The skewness factors (ST) of air temperature tended to become positive above plant canopies and negative within plant canopies. The flatness factors (FT) scatters around 3 through the air layer above and within plant canopies.3) The non-dimensional standard deviations (σw/u*) of vertical velocity had smaller values within plant canopies, compared with those above plant canopies. Within plant canopies, skewness factors (Sw) were negative and flatness factors Fw were greater than 4. The height dependency was in good agreement with that of previous results (Wilson et al. (1982) and Maitani and Seo (1983)).4) The correlation coefficients (rwT) between vertical velocity and air temperature were about 0.3 at the three heights of 260cm, 160cm and 100cm. On the other hand, correlation coefficients (rw·wT) between vertical velocity and instantaneous sensible heat flux were negative within plant canopies. The negative correlation coefficients rw·wT and joint probability densities (w-wT) within plant canopies implys that downdrafts were much efficient for a upward heat flux in the daytime.5) The peak frequencies of power spectrum (nST(n)) of T and cospectrum of (nCowT(n)) at the top of the plant canopies were higher than those within plant canopies. The shapes of nST(n) and nCowT(n) become flatter with decreasing heights within plant canopies.

夏の相模湾沿岸における海陸風の構造

The structure of the land and sea breeze and its diurnal variation were studied by using the data of special field observation performed in the Sagami Bay area in summer of 1980 and 1981. A dynamical analysis was made in order to examine the balances of heat and momentum and the effect of the land slope on the land and sea breeze. It is found that the sea breeze is driven mainly by the land-sea surface temperature difference and has many features of a typical sea breeze. The sea breeze in the developing stage forms a small-scale vertical circulation centered over the coast line, while that in the mature stage forms a part of the "regional-scale sea breeze" which covers the whole Kanto plain. On the other hand, the land breeze is largely affected by the land slope, because the reduced vertical heat transport in the nocturnal atmosphere suppresses the land-sea breeze effect.

A Parameterization of Transient Eddy Heat Flux on a Beta-Plane

Abstract A parameterization of transient eddy heat flux is developed which incorporates baroclinic wave behavior in a continuously stratified fluid on a β-plane. The meridional and vertical heat transports are more sensitive to forced changes in the mean state than suggested by earlier parameterizations. This strong response is analogous to the rapid flux variation in a two-level model near neutral stability. A scheme for applying the parameterization to observed mean zonal flow is suggested and computed fluxes are similar in magnitude and structure to observed eddy heat flux. The flux modeling is consistent with the stronger dependence on meridional temperature gradient and large seasonal variation of the vertical eddy scale observed in lower latitudes.

Simulation of vertical transport of heat and solid particles in fluidized-bed apparatus

An equation for simulating nonstationary vertical transport of heat and solid particles in nonhomogeneous fluidized beds is proposed.

The continental thermal energy storage in a zonally Averaged global thermodynamic model

In the climatic model of Adem (1962,63, 64"a), when the first law of thermodynamics is applied to the continents, the equation is simplified considering a balance between the excess of radiant energy and the loss of thermal energy -sensible and latent heat of evaporation- by vertical turbulent transport, neglecting changes of thermal energy by conduction and storage effects.
 
 In this paper we have attempted to show that the continental storage of energy is not negligible. This finding improves the results of continental surface temperature.
 
 This continental temperature is a function of the temperature of the air near the ground, the cloudiness, the albedo, the solar and terrestrial radiation the absortion coefficients In short wave, the storage of energy and the loss or gain of thermal energy by turbulent vertical transport of sensible and latent heat of evaporation.

A seasonal global climate model with an equivalent meridional atmospheric circulation

A seasonal, zonally averaged, climate model is developed using a hypothetical meridional circulation, which reproduces the atmospheric dynamical heating of a two-level general circulation model. In order to simulate the seasonal temperature cycle, prognostic equations for the land and ocean temperatures are included in the model. The horizontal heat transport in the ocean is modelled as ordinary diffusion. Small-scale vertical transport of sensible and latent heat is described by simple linear terms. For the long-wave radiation calculations, a simple but efficient emissivity approximation scheme is developed. The short-wave radiation treatment is based on an early version of the Mintz-Arakawa general circulation model. The meridional and seasonal variation of the surface temperature as well as the temperature at the two tropospheric levels are simulated quite well by the model. Concerning surface albedo and planetary albedo, the model gives results which are in good agreement with observed values. Radiative fluxes of the model also compare well with observed values. The sensitivity of the model to changes in incoming solar radiation and carbon dioxide content is in accordance with results obtained from other models. The model, with variation of the Earth's orbital parameters, has also been used for some preliminary experiments. DOI: 10.1111/j.2153-3490.1982.tb01840.x

A simple formula for vertical eddy diffusion coefficients under conditions of nonneutral stability

Vertical turbulent transport of heat and momentum in water bodies is often parameterized as the neutral value of the appropriate (vertical) eddy diffusion coefficient, multiplied by a function of the gradient Richardson number. An analysis of previously published formulae for these stability functions shows that they are not consistent with observed values for the ratio between nonneutral and neutral values of the vertical eddy diffusion coefficients [Ueda et al., 1981] nor with observed values of the turbulent Prandtl number or the flux Richardson number [Linden, 1979]. A new formulation for the stability function in the case of turbulent heat transfer is proposed which is of an inverse quadratic form. It is shown that this representation, together with an appropriate inverse linear form in the case of momentum transfer, is in excellent agreement with recent data.

Comparison of Profiles and Fluxes of Heat and Momentum Above and Below an Air-Water Interface

The velocity and temperature fields on both sides of an air-water interface were examined experimentally in order to understand better the physical processes of momentum and heat transfer through the surface layers about the interface. An examination of temperature and velocity profiles plotted in “law-of-the-wall” coordinates leads to the conclusion that, both in the air and in the water, the mechanism of momentum transfer is affected by surface roughness changes, but the mechanism of heat transfer is not. In the water surface layer the velocity fluctuations due to the wave-related motions are of the same order as the purely turbulent motions. The turbulent components closely resemble those found in boundary layers over solid walls. The measured total energy flux from the interface agrees well with the measured single-phase, vertical heat transport through the water surface layer.

Vertical eddy diffusivities in a large tropical lake1

Vertical eddy diffusivities below the thermocline were estimated for Lake Lanao, Philippines, from vertical heat transport. Mean values range from 1.08 cm2·s−1 at 22 m to 0.22 at 44 m. The values are not notably divergent from expected values in temperate lakes of similar sizes and depth.

Sea ice, winter convection, and the temperature minimum layer in the Southern Ocean

The structure of the near surface waters in the Southern Ocean, poleward of the Antarctic Polar Front but away from continental margins, is investigated with a three‐dimensional time‐dependent numerical model which resolves the annual sea ice cycle. The growth and decay of the ice field is predicted, using one of Semtner's (1976) thermodynamic ice models, in terms of specified atmospheric data and computed thermohaline characteristics of the ocean layers. The ice field is found to be sensitive to the lateral advection of heat by the oceanic circulation as well as vertical heat transports due to deep winter convection. The model treats the temperature minimum layer in the Southern Ocean as the remnant of a deep winter mixed layer which becomes capped by surface heating and precipitation in summer. The predicted thermohaline characteristics of the temperature minimum layer and the surface mixed layer are in good agreement with observations. Finally, the annual air‐sea heat exchange predicted by the model is discussed. The model's predicted area averaged heat loss experienced by the ocean south of the Atlantic Polar Front is much smaller than was previously estimated. This is attributed to errors in the southern region of the model domain. It is suggested that models, which include the interactions between sea ice and surface, deep and bottom waters along the continental margins, are needed to investigate this region.

A comparison of tropical oceanic heat fluxes determined by airborne eddy correlation and shipboard bulk aerodynamic techniques

Vertical turbulent transports of latent and sensible heat through the tropical marine boundary layer were measured with ship and airborne instruments in the GATE experimental area. The measurements from the two systems are compared for cases of simultaneous sampling in the same locations during undisturbed weather and during the wakes of convective disturbances. The paired average fluxes from the airborne eddy correlation measurements and the shipboard bulk aerodynamic measurements, for undisturbed weather, are related with correlation coefficients in the range of 0.6 to 0.9; the correlations depend primarily on stratifications of the aircraft data according to sampling altitude (15–153 m msl) and flight pattern relative to the mean wind. The agreement between the two types of measurements is best for ship data paired with aircraft samples from the lowest altitudes (15 and 30 m) and from alongwind rather than crosswind flights, as is appropriate since the stationary ships monitor the alongwind characteristics of the turbulence. The use of long (1–3 hr) versus short (10 min) ship samples did not significantly affect the comparability with the aircraft samples during undisturbed periods.

A note on the development of the thermocline in temperate lakes

Abstract An exact solution has been obtained for a non-linear partial differential equation governing the vertical transport of heat in a lake. The equation, derived and analyzed numerically by Sundaram and Rehm (1971, 1973) is based on a balance between thermal buoyany forces and wind induced turbulence. The exact solution displays the qualitative features of the numerical solution and its representation of the seasonal descent of the thermocline is accurate.