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Latent heat

About: Latent heat is a research topic. Over the lifetime, 13503 publications have been published within this topic receiving 302811 citations.


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TL;DR: The Surface Temperature Initiated Closure (STIC) as discussed by the authors is based on the simultaneous solution of four state equations, including surface temperature, near surface moisture availability (Mf romTS,a ir temperature (TA )a nd relative humidity (RH), and ground heat flux (G).

79 citations

Journal ArticleDOI
TL;DR: In this paper, a physically based representation of surface-moisture availability is proposed, and its applicability is investigated, and it can determine the surface moisture availability on the basis of the basic properties of soils instead of empirical fitting, although further investigations on its practical use are needed.
Abstract: A physically based (i.e., nonempirical) representation of surface-moisture availability is proposed, and its applicability is investigated. This method is based on the surface-resistance approaches, and it uses the depth of evaporating surface rather than the water content of the surface soil as the determining factor of surface-moisture availability. A simple energy-balance model including this representation is developed and tested against wind tunnel experiments under various atmospheric conditions. This model can estimate not only the latent heat flux but also the depth of the evaporating surface simultaneously by solving the inverse problem of energy balance at both the soil surface and the evaporating surface. It was found that the depth of the evaporating surface and the latent heat flux estimated by the model agreed well with those observed. The agreements were commonly found out under different atmospheric conditions. The only limitation of this representation is that it is not valid under conditions of drastic change in the radiation input, owing to the influence of transient phase transition of water in the dry surface layer. The main advantage of the approach proposed is that it can determine the surface moisture availability on the basis of the basic properties of soils instead of empirical fitting, although further investigations on its practical use are needed.

79 citations

Journal ArticleDOI
TL;DR: In this paper, an investigation of the turbulence structure of the lower half of the convective boundary layer over the sea around the UK in a wide variety of meteorological conditions is presented.
Abstract: Results from an investigation of the turbulence structure of the lower half of the convective boundary layer over the sea around the UK in a wide variety of meteorological conditions are presented. The data were obtained on eight flights made by the Hercules aircraft of the Meteorological Research Flight. Differences in structure between boundary layers over sea and over land are emphasized, the most notable being the relatively increased importance of mechanically driven mixing over the sea. This means that a more general scaling scheme is required which retains both u* and zi as scaling parameters. Such a scheme orders the results quite effectively. Dimensionless profiles of momentum, sensible heat and latent heat fluxes are presented, together with dimensionless variance profiles. Excellent agreement is found between these and theoretical predictions from numerical models. Surface fluxes are estimated and compared with bulk aerodynamic formulae. The turbulence statistics are shown to be in good agreement with those published by other workers.

79 citations

Journal ArticleDOI
TL;DR: In this article, a modified version of the simple biosphere model (SiB) was used to investigate the impact of spatial variability in the fields of topography, vegetation cover, and soil moisture on the area-averaged fluxes of sensible and latent heat for an area of 2×15 km (the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) testbed area) located within the FIFE area).
Abstract: A modified version of the simple biosphere model (SiB) of Sellers et al. (1986) was used to investigate the impact of spatial variability in the fields of topography, vegetation cover, and soil moisture on the area-averaged fluxes of sensible and latent heat for an area of 2×15 km (the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) testbed area) located within the FIFE area. This work builds on a previous study of Sellers et al. (1992a) but makes use of a superior data set (FIFE 1989 rather than FIFE 1987) and has a sharper focus on the nonlinear effects of soil wetness on evapotranspiration. The 2×15 km testbed area was divided into 68×501 pixels of 30×30 m spatial resolution, each of which could be assigned topographic, vegetation condition, and soil moisture parameters from satellite and in situ observations gathered in FIFE-89. One or more of these surface fields was area averaged in a series of simulation runs to determine the impact of using large-area means of these initial/boundary conditions on the area-integrated (aggregated) surface fluxes. Prior to these simulations some validation work was done with the model. The results of the study can be summarized as follows: (1) SiB was initialized with satellite and airborne remotely sensed data for vegetation condition and soil wetness, respectively. The surface fluxes calculated by SiB compared well with surface-based and airborne flux observations. (2) Analyses and some of the simulations indicated that the relationships describing the effects of moderate topography on the surface radiation budget are near linear and thus largely scale invariant. The relationships linking the simple ratio (SR) vegetation index, the canopy conductance parameter ∇F, and the canopy transpiration flux are also near linear and similarly scale invariant to first order (see also Sellers et al., 1992a). Because of this it appears that simple area-averaging operations can be applied to these fields with relatively little impact on the calculated surface heat fluxes. (3) The relationships linking surface and root-zone soil wetness to the soil surface and canopy transpiration rates are nonlinear. However, simulation results and observations indicate that soil moisture variability decreases significantly as the study area dries out, which partially cancels out the effects of these nonlinear functions. (4) The near-infrared surface reflectance ρN estimated from atmospherically corrected satellite data may be a better predictor of vegetation condition than a two-band vegetation index, such as the SR, at least for the grasslands represented in the FIFE area. These results support the use of simple averages of topographic and vegetation parameters to calculate surface energy and heat fluxes over a wide range of spatial scales, from a few meters up to many kilometers. Although the relationships between soil moisture and evapotranspiration are nonlinear for intermediate soil wetnesses, the dynamics of soil drying act to progressively reduce soil moisture variability and thus the impacts of these nonlinearities on the area-averaged surface fluxes. These findings indicate that we can use mean values of topography, vegetation condition, and soil moisture to calculate the surface-atmosphere fluxes of energy, heat, and moisture at larger length scales to within an acceptable accuracy for climate-modeling work.

79 citations

Journal ArticleDOI
TL;DR: In this paper, the surface energy balance and ablation at an elevation of 100 m asl on the Ecology Glacier, which is an outlet glacier of the main ice cap of King George Island, Antarctica, were evaluated using a model with input from meteorological data.
Abstract: Meteorological measurements performed during the austral summer of 1990–91 are used to evaluate the surface energy balance and ablation at an elevation of 100 m asl on the Ecology Glacier, which is an outlet glacier of the main ice cap of King George Island, Antarctica. Strong, gusty westerly winds prevail, although occasional south-easterly winds from the Weddell Sea reach the island. Generally, the climate can be characterized as relatively warm and humid with mean summer temperatures well above 0°C. As a result, considerable ablation (0.75 m water equivalent per month) takes place in the lower parts of the Ecology Glacier. The surface energy balance and ablation are calculated using a model with input from meteorological data. In spite of the large amount of cloud (0.83), solar radiation provided most of the energy used for melting (70.3 W m−2). The longwave radiation, sensible heat flux and latent heat flux contributed −9.5, 27.4 and 7.4 W m−2 respectively. Calculations show that a temperature rise of 1°C increases the ablation by almost 15%. This indicates that the ice caps and glaciers currently present on the subantarctic islands and the Antarctic Peninsula may be quite sensitive to climate change.

79 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023581
20221,033
2021640
2020583
2019615
2018578