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Showing papers on "Latent heat published in 1984"


Journal ArticleDOI
TL;DR: In this article, coupled shallow water models are used to simulate this instability which is modulated by the seasonal movements of the atmospheric convergence zones, where the latent heat by the ocean affects the atmosphere in such a manner that the altered surface winds induce the further release of latent heat.
Abstract: During El Nino Southern Oscillation events modest anomalies amplify spatially and temporally until the entire tropical Pacific Ocean and the global atmospheric circulation are affected. Unstable interactions between the ocean and atmosphere could cause this amplification when the release of latent heat by the ocean affects the atmosphere in such a manner that the altered surface winds induce the further release of latent heat. Coupled shallow water models are used to simulate this instability which is modulated by the seasonal movements of the atmospheric convergence zones.

307 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of surface orientation on nucleate boiling heat transfer and proposed two mechanisms of the sensible heat transport by compulsory removal of the thermal layer by the rising bubble and the latent heat transfer by evaporation from thin liquid film underneath the bubble.

191 citations


Journal ArticleDOI
TL;DR: In this article, the latent heat of vaporization of water, Lv, is derived using an analytical approximation to the saturated vapour pressure as a function of temperature, and a new, temperature-dependent function for Lv is derived.
Abstract: Existing formulae and approximations for the latent heat of vaporization of water, Lv, are reviewed. Using an analytical approximation to the saturated vapour pressure as a function of temperature, a new, temperature-dependent function for Lv is derived.

170 citations


Journal ArticleDOI
TL;DR: In this article, the effect on the Bowen ratio of errors in the dry and wet-bulb temperature gradients is analyzed, and it was shown that in very dry conditions the required accuracy in the measurement of these gradients was an order of magnitude greater than could reasonaly be expected for most Bowen ratio equipment.

144 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that after a highly transient stage, crystallization tends toward an equilibrium between heat production (latent heat release) and heat loss, where the nucleation pulses give birth to thermal oscillations.
Abstract: Crystallization at the margin of a quiet cooling magma has been studied numerically, taking into account the kinetics of crystallization. The variables are the latent heat value, the growth and nucleation functions, the initial magma temperature, and the thermal contrast between magma and country rock. We have investigated a wide range of values for these parameters corresponding to natural conditions. We show that after a highly transient stage, crystallization tends toward an equilibrium between heat production (latent heat release) and heat loss. Given the small diffusivity of country rocks, latent heat release is the main factor controlling the temperature evolution. In order to minimize the latent heat release, crystallization occurs at a temperature where nucleation is small. This can be close to either the liquidus or the solidus, depending on the initial conditions. The main process controlling crystallization is nucleation and not crystal growth. Nucleation occurs as a series of sharp pulses followed by longer periods of crystal growth. The nucleation pulses give birth to thermal oscillations. These oscillations can be sustained if the interior magma temperature is above the liquidus independently of the heat loss mechanism. We show that the phenomenon occurs on the scale of a few centimeters which corresponds to the inch-scale layering of many ultrabasic complexes. The model allows us to calculate crystal sizes which are in good agreement with geological observations. The crucial parameters which determine crystal size variations near the margins of igneous bodies are the initial thermal conditions as well as the nucleation and growth functions. In the main cooling regime close to the liquidus, significant size variations can be created by small thermal disturbances.

135 citations


Journal ArticleDOI
TL;DR: In this paper, an analysis of moisture and mean tropospheric enthalpy distributions based on FGGE data is described and interpreted for the months of May and June 1979 using 15-day means for the region 0-150°E, 40°S−40°N, and detailed temporal evolutions from time series at daily intervals for two regions-the Arabian Sea and the larger area 0°−150° E, 22.5°5−41.25°N.
Abstract: Analyses of moisture and mean tropospheric enthalpy distributions based on FGGE data are described and interpreted for the months of May and June 1979. Their detailed spatial characteristics are inferred using 15-day means for the region 0–150°E, 40°S–40°N, and the detailed temporal evolutions from time series at daily intervals for two regions-the Arabian Sea and the larger area 0°–150°E, 22.5°5–41.25°N. Vertical motion fields are calculated using O'Brien's method and are used to determine the distributions of moisture convergence and heating. The onset is found to consist of two main phases: 1) a moisture buildup over the Arabian Sea during which synoptic- and mesoscale transient disturbances develop; the relationship of this buildup with planetary wave activity is discussed. This is followed by 2) a rapid intensification of the Arabian Sea winds and a substantial increase in latent heat release, essentially a large-scale feedback process. The fully established monsoonal flow is interpreted in ...

113 citations


Journal ArticleDOI
TL;DR: In this article, the monthly surface heat budget and wind stress are calculated from three-hourly meteorological data obtained at OWS B from 1946 to 1974 using formulae based on the best available measurements, and are then compared with earlier estimates.
Abstract: The monthly surface heat budget and wind stress are calculated from three‐hourly meteorological data obtained at OWS B from 1946 to 1974 using formulae based on the best available measurements, and are then compared with earlier estimates. The surface heating is compared with the monthly heat storage in the water column calculated from hydrographic casts from 1964 to 1973. In spite of the scatter in the individual monthly heat storage values, the mean seasonal cycle agrees well with that of the surface flux. The residual, attributed to advection, is highly variable and does not have a strong seasonal cycle at this location. The long‐term heat loss from the ocean to the atmosphere at OWS B is found to be 28 W m−2, much smaller than the 98 W m−2 loss computed from the same data using Bunker's widely accepted formulae. The difference is accounted for by Bunker's 28% underestimate of the incoming short‐wave radiation and his 74 and 43% overestimates of the outgoing sensible and latent heat fluxes, re...

108 citations


Journal ArticleDOI
TL;DR: This paper found that between 80% and 90% of the total soil heat storage is involved in the latent heat exchange accompanying thawing and freezing in both forest and tundra.
Abstract: Forest and tundra soils display distinctive microclimates for a climatically normal year at Churchill. Forest soils are substantially warmer in the active layer than those of the tundra but the tundra active layer is deeper. Forest soils are much wetter than those of the tundra. This results from the deep winter snow pack, which provides abundant meltwater to already thawed soils. The soils remain wet throughout the year, and the large latent heat release delays the freezing of forest soils until a snow pack is established. As a result, soils stay relatively warm throughout winter and thaw rapidly and deeply before snow pack melting in the spring. The thaw period in the tree rooting zone is about 6 months, compared to 4 months at the same depth in tundra. The magnitude of soil heat storage is large, comprising 18% and 16% of net radiation in tundra and forest, respectively, during the thaw season. During freeze back it is the dominant heat exchange process. Between 80% and 90% of the total soil heat storage is involved in the latent heat exchange accompanying thawing and freezing. Soil heat flux plates strongly underestimate the ground heat exchange and are unreliable in permafrost terrain.

89 citations


Journal ArticleDOI
TL;DR: In this article, the authors used eddy correlation equipment to measure mass and energy fluxes over a soybean crop and found that the crop did not appear to be light-saturated at PAR flux densities < 1800 ΘEi m−2 s−1.
Abstract: Eddy correlation equipment was used to measure mass and energy fluxes over a soybean crop. A rapid response CO2 sensor, a drag anemometer, a Lyman-alpha hygrometer and a fine wire thermocouple were used to sense the fluctuating quantities. Diurnal fluxes of sensible heat, latent heat and CO2 were calculated from these data. Energy budget closure was obtained by summing the sensible and latent heat fluxes determined by eddy correlation which balanced the sum of net radiation and soil heat flux. Peak daytime CO2 fluxes were near 1.0 mg m−2 (ground area) s−1. The eddy correlation technique was also employed in this study to measure nocturnal CO2 fluxes caused by respiration from plants, soil, and roots. These CO2 fluxes ranged from - 0.1 to - 0.25 mg m−2s−1. From the data collected over mature soybeans, a relationship between CO2 flux and photosynthetically active radiation (PAR) was developed. The crop did not appear to be light-saturated at PAR flux densities < 1800 ΜEi m−2 s−1. The light compensation point was found to be about 160 ΜEi m−2 s−1.

89 citations


Journal ArticleDOI
TL;DR: In this paper, a simple statistical technique is described to determine monthly mean marine surface-layer humidity, which is essential in the specification of surface latent heat flux, from total water vapor in the atmospheric column measured by space-borne sensors.
Abstract: A simple statistical technique is described to determine monthly mean marine surface-layer humidity, which is essential in the specification of surface latent heat flux, from total water vapor in the atmospheric column measured by space-borne sensors. Good correlation between the two quantities was found in examining the humidity soundings from radiosonde reports of mid-ocean island stations and weather ships. The relation agrees with that obtained from satellite (Seasat) data and ship reports averaged over 2 deg areas and a 92-day period in the North Atlantic and in the tropical Pacific. The results demonstrate that, by using a local regression in the tropical Pacific, total water vapor can be used to determine monthly mean surface layer humidity to an accuracy of 0.4 g/kg. With a global regression, determination to an accuracy of 0.8 g/kg is possible. These accuracies correspond to approximately 10 to 20 W/sq m in the determination of latent heat flux with the bulk parameterization method, provided that other required parameters are known.

88 citations


01 Dec 1984
TL;DR: In this article, a simple algorithm incorporating the equivalent heat capacity model was described for the finite-difference heat transfer analysis involving melting and solidification, and the latent heat of fusion was analyzed.
Abstract: A simple algorithm incorporating the equivalent heat capacity model is described for the finite-difference heat transfer analysis involving melting and solidification. The latent heat of fusion is ...

Journal ArticleDOI
TL;DR: In this paper, the authors consider whether the omission of these processes is justified within the context of quantitatively determining regional climatic changes, and they also consider the effects of snow cover on conductivity and surface albedo and of oceanic heat flux on bottom ablation.
Abstract: Recent work in modelling climatic changes due to increased atmospheric CO2 has shown the maximum change to occur in the polar regions as a result of seasonal reductions in sea ice coverage. Typically, sea ice thermodynamics is modelled in a very simple way, whereby the storage of both sensible and latent heat within the ice is ignored, and the effects of snow cover on conductivity and on surface albedo and of oceanic heat flux on bottom ablation may also be neglected. This paper considers whether omission of these processes is justified within the context of quantitatively determining regional climatic changes. A related question, whether omission of ice dynamics can be justified, is not considered.

Journal ArticleDOI
TL;DR: In this article, the surface energy budget of a snowpack in an alpine basin near the Main Divide of New Zealand's South Island was calculated from meteorological observations during a spring melt period.
Abstract: The surface energy budget of a snowpack in an alpine basin near the Main Divide of New Zealand's South Island was calculated from meteorological observations during a spring melt period. The sensible and latent heat exchanges account for 82% of the energy used for melting snow, net radiation accounts for 16% and the sensible heat of rain for 2%. Regression analysis shows that indices of airmass characteristics and regional circulation explain most of the variances in the observed temperature and wind at the site, which are the major controls on turbulent exchange. Local advection of heat is important during periods of strong insolation. Local thermally-generated winds enhance turbulent exchange over the snowpack during calm, anticyclonic periods. The airmass and regional circulation indices account for 75% of the variance in the daily totals of sensible plus latent heat flux. These results support the utility of large-scale indices for forecasting snowmelt during flood-producing rain-on-snow events.

Journal ArticleDOI
TL;DR: In this article, a modification is made to the conventional evaporation equation to allow the calculation of Evaporation from saline lakes, and the modified equation shows how, for a given set of meteorological conditions, the evapse rate, the partitioning of available energy into sensible and latent heat, and surface temperature, can all be related to solute concentrations.
Abstract: A modification is made to the conventional evaporation equation to allow the calculation of evaporation from saline lakes. The modified equation shows how, for a given set of meteorological conditions, the evaporation rate, the partitioning of available energy into sensible and latent heat, and the surface temperature, can all be related to solute concentrations. To illustrate the operation of the equation the recent and proposed changes to the hydrology of the Dead Sea were used as a case study.

Journal ArticleDOI
Eiji Ohtaki1
TL;DR: In this paper, a calibration equation and some results of the field performance of an infrared instrument, which is designed to measure simultaneous fluctuations of atmospheric carbon dioxide and water vapor, are described.
Abstract: A calibration equation and some results of the field performance of an infrared instrument, which is designed to measure simultaneous fluctuations of atmospheric carbon dioxide and water vapor, are described. Field observations show that the instrument is suitable for simultaneous measurement of turbulent fluxes of carbon dioxide and water vapor in conjunction with a sonic anemometer. Measured values of carbon dioxide and water vapor fluxes show diurnal variations characterized by crop activity with respect to assimilation, respiration and evapotranspiration. Carbon dioxide is transferred downward during the daytime and upward at night, while latent heat and sensible heat are transferred in the opposite sense. The non-dimensional gradient of carbon dioxide is expressed in the following form under weak unstable conditions: Φc= (1 − 16ζv)-1/2. Here, ζv is the Monin-Obukhov stability parameter including the humidity effect. This relation was originally proposed for temperature and humidity. Thus, the results indicate that the turbulent mechanisms of carbon dioxide fluctuations are similar to those of other scalar entities. This is strongly supported by the high correlation coefficient found between fluctuations of carbon dioxide and temperature or humidity in the air layer over crop fields.

Journal ArticleDOI
TL;DR: In this article, the authors used a computer program to simulate drying in a malt kiln with specific heat, heat transfer coefficient, shrinkage, latent heat of vaporization and thin-layer drying equations.

Patent
07 Mar 1984
TL;DR: In this article, the authors describe a process for the recovery and reuse of heat contained in the wet exhaust gases emanating from a solids dryer or liquor concentrator, particularly one in which drying or concentration is facilitated by purging the vapor with some non-condensable gas such as air or nitrogen, water or solvent vapor in the moist exhaust mixture is separated from the noncondensable gases or gases by preferentially passing the vapor through a semipermeable membrane.
Abstract: In a process for the recovery and reuse of heat contained in the wet exhaust gases emanating from a solids dryer or liquor concentrator (1), particularly one in which drying or concentration is facilitated by purging the vapor with some noncondensable gas such as as air or nitrogen, water or solvent vapor in the moist exhaust mixture is separated from the noncondensable gas or gases by preferentially passing the vapor through a semipermeable membrane (2). The water or solvent vapor is then compressed and subsequently condensed in a heat exchanger (4), permitting recovery of its latent heat of vaporization for reuse in the evaporation process. In a drying process, this recovered energy is conveniently used to reheat the dry gases that exit from the membrane separator (2), permitting the hot, dry gases to be recirculated through the dryer (1). Alternatively, an indirect heat exchanger may be used to transfer this heat to the material being dried. In an evaporative process forthe concentration of a liquor, the recovered energy may be used either to preheat the dry purge gases or to heat the dilute liquor being concentrated.

Journal ArticleDOI
Brian P. Flannery1
TL;DR: In this article, the authors consider a two phase model, in which they allow for transport of both thermal energy of air and latent heat associated with water vapor, and use this model to calculate climate change, i.e., ΔT(x), as a function of varying insolation and changing concentration of atmospheric CO2 under the assumption that relative humidity does not change.
Abstract: Standard latitudinally resolved energy balance models describe conservation of energy on a sphere subject to solar heating, cooling by infrared radiation and diffusive redistribution of energy according to a Fourier type heat flow with flux proportional to the gradient of temperature. The model determines the distribution of temperature with latitude T(x). Here we consider a similar model, the two phase model, in which we allow for transport of both thermal energy of air and latent heat associated with water vapor. We use the two phase model to calculate climate change, i.e., ΔT(x), as a function of varying insolation and changing concentration of atmospheric CO2 under the assumption that relative humidity does not change. We compare the results with calculations from standard energy balance models and general circulation models. The distribution of warming with latitude for doubled atmospheric CO2 found with the two phase model agrees far better with the pattern of warming found in GCM studies t...

Journal ArticleDOI
TL;DR: In this article, the operating characteristics of Glauber's salt as a heat storage medium were studied in a pilot heat storage system using direct phase contact heat exchange, and the effect of several variables was studied over many complete cycles of the unit, including variable HTF flow rate and inlet temperature, wall insulation, internals to redisperse the HTF and prolonged shutdown of the system.

Journal ArticleDOI
J. Chen1
TL;DR: In this paper, the sensible heat flux density C and the latent heat flux densities λE were coupled in the case of a multi-layer model of vegetation, and two electrical analogues, for H and J, were designed, equivalent to the resistance scheme for C and E, but uncoupled.
Abstract: The sensible heat flux density C and the latent heat flux density λE are coupled in the case of a multi-layer model of vegetation. Therefore two linearly independent combinations of C and λE, the enthalpy flux density H and the saturation heat flux density J, are introduced. Two electrical analogues, for H and J, are designed. They are equivalent to the resistance scheme for C and λE, but uncoupled. Penman's formulas for C and λE, which are applicable only to single-layer models, can be expressed equivalently in terms of H and J. This version of Penman's formulas can be extended easily to multi-layer canopies.

Journal ArticleDOI
TL;DR: In this paper, the energy balance components of net radiation, ground heat flux, and latent and sensible heat fluxes for upland tundra near the Hudson Bay coast at Churchill were measured continuously between April 25 and September 6, 1979.
Abstract: Energy balance components of net radiation, ground heat flux, and latent and sensible heat fluxes for upland tundra near the Hudson Bay coast at Churchill were measured continuously between April 25 and September 6, 1979. The measurements indicate a strong regional advective effect. In the premelt period during cold onshore winds, net radiation was very small and the other energy balance components were negligible. Under offshore warmer winds, net radiation was large, as were the other fluxes, especially the ground heat flux. In the postmelt period with cold onshore winds, sensible heating of the atmosphere was large and heating of the ground was suppressed. For offshore winds, ground heating was large and atmospheric heating was suppressed. The magnitude of net radiation and the latent heat flux were little affected by wind direction in the postmelt period. The implications of the results are discussed with respect to the potential effects of climatic cooling and warming.

Patent
11 May 1984
TL;DR: In this article, a starting solution is concentrated to a desired end solution by contacting the starting solution with a gaseous medium under the conditions that the heat content of the initial solution in contact with the medium is smaller than the heat of the medium, and the duration of contacting is such that most of the solution that evaporates does so under conditions of constant enthalpy.
Abstract: A starting solution is concentrated to a desired end solution by contacting the starting solution with a gaseous medium under the conditions that the heat content of the starting solution in contact with the gaseous medium is smaller than the heat content of the medium, and the duration of contacting is such that most of the solution that evaporates does so under conditions of constant enthalpy. When the starting solution is a brine, and the gaseous medium is air whose relative humidity is less than the relative humidity at the air/brine interface, the brine can be sprayed into the air to form a shower of droplets within which heat and vapor transfer take place during the transit time of the droplets in the air. When the ratio of droplets to air is sufficiently small, the heat content of the droplets is much smaller than the heat content of the air. When the temperature of the brine exceeds the wet-bulb temperature of the air, the latent heat flux is greater than the sensible heat flux, and the temperature of the droplets rapidly approaches the wet-bulb temperature of the air as the droplets are cooled by evaporation. Once the wet-bulb temperature at the air/brine surface is substantially equal to the wet-bulb temperature of the air, a different process takes place, wherein the latent heat flux is substantially equal to the sensible heat flux, and the temperature of the brine approaches the temperature of the air without involving a change in enthalpy.

Journal ArticleDOI
TL;DR: The application of a microcomputer-based sampling system for measuring the flux densities of radiation, soil heat, sensible heat, latent heat, carbon dioxide and momentum provides real-time measurements of flux density required to estimate CO 2 exchange between the atmosphere and crops.

Journal ArticleDOI
TL;DR: Based on Pitzer's three-parameter corresponding states principle, this article developed a correlation of the latent heat of vaporization of aromatic coal liquid model compounds for a temperature range from the freezing point to the critical point.
Abstract: Based on Pitzer's three-parameter corresponding states principle, the authors have developed a correlation of the latent heat of vaporization of aromatic coal liquid model compounds for a temperature range from the freezing point to the critical point. An expansion of the form L = L/sub 0/ + ..omega..L /sub 1/ is used for the dimensionless latent heat of vaporization. This model utilizes a nonanalytic functional form based on results derived from renormalization group theory of fluids in the vicinity of the critical point. A simple expression for the latent heat of vaporization L = D/sub 1/epsilon /SUP 0.3333/ + D/sub 2/epsilon /SUP 0.8333/ + D/sub 4/epsilon /SUP 1.2083/ + E/sub 1/epsilon + E/sub 2/epsilon/sup 2/ + E/sub 3/epsilon/sup 3/ is cast in a corresponding states principle correlation for coal liquid compounds. Benzene, the basic constituent of the functional groups of the multi-ring coal liquid compounds, is used as the reference compound in the present correlation. This model works very well at both low and high reduced temperatures approaching the critical point (0.02 < epsilon = (T /SUB c/ - T)/(T /SUB c/- 0.69)). About 16 compounds, including single, two, and three-ring compounds, have been tested and the percent root-mean-square deviationsmore » in latent heat of vaporization reported and estimated through the model are 0.42 to 5.27%. Tables of the coefficients of L/sub 0/ and L/sub 1/ are presented. The contributing terms of the latent heat of vaporization function are also presented in a table for small increments of epsilon.« less

01 Jan 1984
TL;DR: In this paper, Goudriaan et al. developed a more elegant mathematical analysis that both deepens the understanding of the processes involved, and enables the writing of more efficient computer programs.
Abstract: In crop micrometeorology the transfer of radiation, momentum, heat and mass to or from a crop canopy is studied. Simulation models for these processes do exist but are not easy to handle because of their complexity and the long computing time they need. Moreover, up to now such models can only be run on mainframe computers. This study aims at developing a more elegant mathematical analysis that both deepens the understanding of the processes involved, and enables the writing of more efficient computer programs. To model the radiation regime, Goudriaan (1977) divided the crop canopy into several layers. The radiation at each layer was classified into downward and upward flux densities, assigned to nine contiguous zones in a hemisphere. Then a set of equations was derived for these radiation components and an efficient iteration method was developed to solve them. The solutions gave a detailed description of the distribution of the radiation in a canopy, from which the zonal reflectance from a canopy can also be obtained. In addition, by computer experimentation a so- called reciprocity relation was found between a direct light source and the reflected radiance from vegetation. This relation has potential applications in remote sensing techniques. Remaining problems are: (a) the computation of the radiation profiles in a canopy needs much execution time; (b) azimuthal variations of bidirectional reflectance from a canopy cannot be simulated; and (c) the mathematical proof of the reciprocity relation was not found. In Chapters 2 and 3, the downward and upward radiation from all directions in a hemisphere are represented by radiation vectors and the interactions of the radiation with a horizontally homogeneous canopy layer are represented by reflectance and transmittance matrices. In Chapter 2, the physical process of the reflection and transmission of radiation by a multi-layer canopy is examined under vector-matrix notation. The radiation vector incident upon the top of a canopy, may be directly reflected from the first layer forming a component of the reflected radiation vector from the top of the canopy; or it may, for instance, be transmitted through the first layer, reflected from the second layer, and transmitted again through the first layer, forming another component of the reflected radiation vector. Not every reflection-transmission series, called a radiation path, results in a component of the reflected radiation vector but there is an infinite number of such paths. It is proven in Chapter 2 that the reciprocity relation holds if each radiation path contributing to the reflection vector can be reversed and also result in a component of the reflected radiation vector. It is shown that this reversibility of the radiation paths is generally true for reflection whereas for transmission a vertically uniform canopy and a black soil surface are required. In Chapter 3, the radiation equations are rewritten as a set of difference equations with vectors as variables and matrices as coefficients. Then two differential equations for downward and upward radiation vectors are derived, where the coefficients are interception, backward and forward scattering matrices, which are the three basic matrices characterizing the interactions of a horizontally homogeneous canopy with radiation vectors. These two differential equations are, in fact, the vector-matrix version of the Kubelka-Munk equations, which are two scalar differential equations for total downward and upward radiation intensities in a canopy with horizontal Lambertian leaves. The extended Kubelka-Munk equations can describe the directional transfer of radiation in a canopy with non-Lambertian leaves and any leaf inclination distribution. This is more realistic than Suits' (1972) model containing, principally, only vertical and horizontal leaves. The azimuthal variations are included by extending the corresponding vectors and matrices. The analytical solutions for profiles of the downward and upward radiation vectors are found by means of a standard matrix method and also the bidirectional reflectance from a canopy is thus obtained. In spite of the availability of the analytical solution to the bidirectional reflectance from a canopy, however, the azimuthal resolution is still restricted by the execution time. Thus, for leaf canopies without azimuthal preference a special method reducing the dimensions of the relevant matrices, and an approximate method based on the radiation path method presented in Chapter 2 are developed. The approximate method allows the resolution of 10 degrees in azimuth as well as in inclination, and calculates the bidirectional reflectance from a canopy within an acceptable execution time. In Chapters 4 to 7, profiles of temperature, humidity, sensible and latent heat flux densities in a canopy are studied in detail. Because the derived equations for sensible and latent heat flux densities are coupled with each other, they must be solved simultaneously. This leads to the following problems: (a) it costs much execution time and space so the program cannot be executed on a microcomputer; (b) distinction of sunlit and shaded leaves within each layer would require to split each layer into several sublayers according to different irradiation levels and thus increase further the execution time and space; (c) the analytical expressions for total sensible and latent heat flux densities above a canopy are not available so that it is not possible to find relationships between the parameters used in the multi-layer model and those used in the single- layer model (Penman- Monteith approach), viz. the canopy resistance and the excess resistance. In Chapter 4, the sensible and latent heat flux densities are replaced by the enthalpy flux density H, which is the sum of the sensible and latent heat flux densities, and by the saturation heat flux density J, which is a weighted difference between the sensible heat flux density and the latent heat flux density. This weight is done in such a way that the resulting equations for H and J are now mutually independent, so that the computation of the relevant profiles is greatly simplified. Two uncoupled electrical analogues for H and J, respectively, are designed, which are the counterparts of the coupled electrical analogue for the sensible and latent heat. The computation of the J profile is further simplified by recurrent formulas. Moreover, in terms of H and J, the well known Penman's formulas are expressed in a unified form applicable to both single- and multi-layer models, which provides a bridge between these two models. In Chapter 5, a method to distinguish sunlit and shaded leaves is developed based on the two uncoupled electrical analogues for H and J and on the recurrent formulas developed in Chapter 4. Goudriaan's (1977) simulation program MICROWEATHER is then rewritten in BASIC. A complete list of the program and the symbols used in the program is given in the Appendix. This program in BASIC gives the same detailed description of the crop micrometeorology as MICROWEATHER does, while it can be executed on a microcomputer. The agreement between the results of these two programs is good. In Chapter 6, Monteith's (1963) extrapolation method to obtain representative surface values of temperature and vapour pressure is extended by replacing the vapour pressure profile by the dew- point temperature profile. Thus, the canopy resistance can be obtained directly by graphical means. Two basic parameters of the single-layer model, the canopy resistance and the excess resistance, are clearly presented in this way. In Chapter 7, the canopy resistance and the excess resistance are calculated from the parameters used in the multi-layer model by means of the unified Penman's formulas developed in Chapter 4. The formulas derived for these two resistances show that both of them contain aerodynamic and physiological components. It is shown that however, for a dense canopy with a dry soil surface, the canopy resistance contains mainly physiological components and is approximately equal to the resistance value calculated as all stomatal resistances of the leaves connected in parallel; the excess resistance contains mainly aerodynamic components and is a simple function of the friction velocity. In this case, therefore, the canopy resistance and the excess resistance can be estimated easily in 'terms of the parameters used in the multi-layer model. In the discussion in Chapter 8, it is emphasized that the method to calculate bidirectional reflectance from a canopy developed in Chapter 3 can have important applications in remote sensing of vegetation, because it allows to study the effects of different leaf inclination distributions and non-Lambertian leaves. The results should be compared with data sets on the bidirectional reflectance from various vegetation canopies to see the practical significance of these two factors. The simulation program for crop micrometeorology developed for microcomputers (Chapter 5) can be used for short grass, where Goudriaan's MICROWEATHER has difficulties with the execution time caused by the small time coefficient of the model. The model can be further developed to simulate the evapo-transpiration from a canopy wetted by rainfall, and it could be incorporated into a pest and plant disease model. The results obtained on the canopy resistance and excess resistance (Chapter 7) justify the applicability of the single-layer model for a dense canopy. But for a sparse canopy the influence of the soil surface cannot be neglected, and the double-layer model one represents the canopy and the other represents the soil surface should be used. This version of the micrometeorological simulation program may be included in a crop growth model such as BACROS (de Wit et al., 1978).

Journal ArticleDOI
TL;DR: In this paper, the latent heat of melting was taken into account by introducing the apparent enthalpy as a function of the fraction of liquid formed which can be derived from equations describing non-equilibrium melting.

Journal ArticleDOI
TL;DR: In this article, the authors used real-data numerical simulation experiments to investigate the latent heat induced energy transformations during the development of the wave cyclone of 20 May 1977 and found that latent heat enhanced the generation of kinetic energy at all levels, slightly weakened its dissipation (to sub-grid scales) in the lower troposphere and increased this dissipation in the upper troposphere.
Abstract: Using real-data numerical simulation experiments, latent heat induced energy transformations during the development of the wave cyclone of 20 May 1977 are investigated. During a 24 h period over 5 cm of precipitation fell despite baroclinically inactive synoptic conditions. The numerical experiments which were conducted included two 24 h fine-mesh forecasts, one with and the other without latent heating. The following conclusions resulted from kinetic energy budget calculations performed on isobaric surfaces at 100 mb increments from 900 mb to 100 mb. 1) Heating enhanced the generation of kinetic energy at all levels, slightly weakened its dissipation (to sub-grid scales) in the lower troposphere and increased this dissipation in the upper troposphere. 2) Because of the rapid increase of kinetic energy with height the latent heat's contribution to the kinetic energy balance was, in a relative sense, most significant in the lower troposphere. It is shown that while the maximum latent heating rates...

Journal ArticleDOI
TL;DR: This article investigated the influence of stable and convective latent heat release on synoptic-scale vertical motions and the corresponding evolution of an extratropical cyclone during a 48-hour period of strong development.
Abstract: This study investigates the influence of stable and convective latent heat release on synoptic-scale vertical motions and the corresponding evolution of an extratropical cyclone during a 48 h period of strong development. The cyclone's early evolution was dominated by dry dynamical processes. By midway through the period, however, forcing by latent heat release accounted for over 50 percent of the upward vertical motions, with the convective component dominating. The cyclone's development was most intense during the second 24 h, despite a decrease in latent heat release. During the latter period, the reduced direct latent heat influence may have been augmented by an indirect influence, in which pre-existing dry dynamical forcing was enhanced by diabatic intensification of vorticity and thermal gradients.

BookDOI
01 Jan 1984
TL;DR: In this article, the authors proposed a sampling strategy for estimating the global statistics of mesoscale eddies in the Southern Ocean from Satellites from the past history to future sensors.
Abstract: Large Scale Oceanographic Experiments.- A Concept of WOCE.- TOGA Overview.- Altimetry.- Potential Future Altimetry Mission: A Joint NASA-CNES Effort.- A Sampling Strategy for Altimeter Measurements of the Global Statistics of Mesoscale Eddies.- Eddy Kinetic Energy Distribution in the Southern Ocean from Seasat Altimeter and FGGE Drifting Buoys.- Sea Surface Temperature.- Satellite Measurements of Sea-Surface Temperature for Climate Research.- Satellite Sea Surface Temperature Determination from Microwave and Infrared Radiometry.- Wind and Stress.- Ocean Surface Wind Stress.- Wind Speed and Stress over the Ocean: Scatterometer versus Surface Measurements.- A Summary of the Wind Data Available from Satellites from the Past History to Future Sensors.- Surface Heat Flux.- Large Scale Surface Heat Fluxes.- Earth Radiation Budget Observations, Old and New.- Surface Radiation Budget.- Estimation of Latent Heat Flux with Seasat-SMMR, a Case Study in N. Atlantic.- The Determination of Surface Fluxes of Heat and Water by Satellite Microwave Radiometry and in situ Measurements.- The Solar Heat Input into the Upper Marine Environment.- Summary of Discussion and Recommendations.- Altimetry.- Sea-Surface Temperature.- Surface Wind Velocity and Stress.- Ocean Surface Heat Flux.- Precipitation.- Acronyms and Definitions.- List of Participants.

Journal ArticleDOI
TL;DR: A numerical algorithm for the computation of the temperature profile induced by a pulsed laser beam has been developed by means of the quasi-implicit technique, and the effect of the latent heat of fusion was included in the temperature calculation.
Abstract: A numerical algorithm for the computation of the temperature profile induced by a pulsed laser beam has been developed by means of the quasi-implicit technique. In this calculation the effect of the latent heat of fusion was included in the temperature calculation. Some examples are given to demonstrate the utility of the numerical technique for calculating temperature profiles in optical recording media. The effects of various thermodynamic properties of recording media are apparent in the examples presented in this work, and the result of the calculated temperature information can be readily applied to the study of the writing mechanism. Extensions to a multilayered thin film system can be easily done simply by modifying the matrix elements which involve the interfacial layers.