Latent heat

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

Enhanced temperature variability in high-altitude climate change

Abstract: In the present article, monthly mean temperature at 56 stations assembled in 18 regional groups in 10 major mountain ranges of the world were investigated. The periods of the analysis covered the last 50 to 110 years. The author found that the variability of temperature in climatic time scale tends to increase with altitude in about 65 % of the regional groups. A smaller number of groups, 20 %, showed the fastest change at an intermediate altitude between the peaks (or ridges) and their foot, while the remaining small number of sites, 15 %, showed the largest trends at the foot of mountains. This tendency provides a useful base for considering and planning the climate impact evaluations. The reason for the amplification of temperature variation at high altitudes is traced back to the increasing diabatic processes in the mid- and high troposphere as a result of the cloud condensation. This situation results from the fact that the radiation balance at the earth’s surface is transformed more efficiently into latent heat of evaporation rather than sensible heat, the ratio between them being 4 to 1. Variation in the surface evaporation is converted into heat upon condensation into cloud particles and ice crystals in the mid- and high troposphere. Therefore, this is the altitude where the result of the surface radiation change is effectively transferred. Further, the low temperature of the environment amplifies the effect of the energy balance variation on the surface temperature, as a result of the functional shape of Stefan–Boltzmann law. These processes altogether contribute to enhancing temperature variability at high altitudes. The altitude plays an important role in determining the temperature variability, besides other important factors such as topography, surface characteristics, cryosphere/temperature feedback and the frequency and intensity of an inversion. These processes have a profound effect not only on the ecosystem but also on glaciers and permafrost.

A Mesoseale Numerical Model of Lake-Fffect Storms

Abstract: The atmospheric structure upwind of the Great takes during arctic air outbreaks is represented by three layers: a lower constant flux layer in contact with the ground, a well-mixed planetary boundary layer surmounted by an inversion, and a deep stratum of overlying stable air. The set of primitive equations is averaged through the depth of the mixed layer to yield predictive equations for the horizontal components of velocity, potential temperature and specific humidity in the layer, and the height of the inversion. Interactions between the well-mixed convective layer and both the underlying and overlying layers are parameterized so that time-dependent calculations can be limited to a single layer. Precipitation from cumulus clouds within the layer is represented in terms of the mesoscale variables and latent heat is included. The equation set has been solved numerically for a 2000-point grid mesh centered on Lake Erie. Grid separation was 6 km in the cross-lake direction and 12 km along the lake...

A review of thermal energy storage technologies and control approaches for solar cooling

Abstract: This paper presents a review of thermal storage media and system design options suitable for solar cooling applications. The review covers solar cooling applications with heat input in the range of 60–250 °C. Special attention is given to high temperature (>100 °C) high efficiency cooling applications that have been largely ignored in existing reviews. Sensible and latent heat storage materials have been tabulated according to their suitability for double effect and triple effect chillers. A summary of system designs for water storage (sensible heat), and phase change material storage (latent heat) has been provided. The article summarizes literature related to solar thermal air-conditioning systems from a material level as well as plant level considerations. This includes evaluating various control strategies for managing the thermal store, that aid in optimal functioning of a solar air conditioning plant. Modeling approaches are reviewed for sizing the solar thermal store, highlighting the large difference seen in specific storage size when applied in different applications.

Simulating fluxes from heterogeneous land surfaces: Explicit subgrid method employing the biosphere‐atmosphere transfer scheme (BATS)

Abstract: A vectorized version of the biosphere-atmosphere transfer scheme (VBATS) is used to study moisture, energy, and momentum fluxes from heterogeneous land surfaces st the scale of an atmospheric model (AM) grid cells. To incorporate subgrid scale inhomogeneity, VBATS includes two important features: (1) characterization of the land surface (vegetation and soil parameters) at N subgrid points within an AM grid cell and (2) explicit distribution of climate forcing (precipitation, clouds, etc.) over the subgrid. In this study, VBATS is used in stand-alone mode to simulate a single AM grid cell and to evaluate the effects of subgrid scale vegetation and climate specification on the surface fluxes and hydrology. It is found that the partitioning of energy can be affected by up to 30%, runoff by 50%, and surface stress in excess of 60%. Distributing climate forcing over the AM grid cell increases the Bowen ratio, as a result of enhanced sensible heat flux and reduced latent heat flux. The combined effect of heterogeneous vegetation and distribution of climate is found to be dependent on the dominat vegetation class in the AM grid cell. Development of this method is part of a larger program to explore the importance of subgrid scale processes in regional and global climate simulations.