Latent heat

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

Mesoscale Numerical Study of Two Cases of Long-Lived Quasi-Stationary Convective Systems over Eastern Spain

Abstract: A set of mesoscale numerical simulations using the Pennsylvania State University‐National Center for Atmospheric Research model is used to investigate two cases of extreme precipitation over eastern Spain. Both cases (3‐4 November 1987 and 20 October 1982) were characterized by quasi-stationary mesoscale convective systems that developed over the Valencia region and lasted more than 30 and 12 h, respectively. Rainfall totals in 24 h exceeded 800 mm on 3‐4 November and 400 mm on 20 October at some localities of that region. The first event occurred within a weak and very stagnant synoptic pattern under a persistent easterly/northeasterly low-level jet stream impinging on the Valencian orography. In contrast, the second case involved a westwardmoving surface low driven by an upper-level jet streak, which evolved along the northern edge of an upperlevel cutoff low over North Africa. In both cases, the mesoscale model forecast spatial details of the precipitation field reasonably accurately, as well as capturing its long duration, but underestimated the storm total precipitation. Model output fields suggest that the development of a surface mesolow by latent heat release, as well as lee cyclogenesis induced by the Atlas Mountains, could have played an important role in both events by providing low-level convergence and enhanced upslope winds. Thus, a factor separation technique is used to explore this issue. For the event of 3‐4 November 1987, latent heat is decisive for explaining the precipitation maximum over central Valencia, and the Atlas orography induces rainfall enhancement over the same zone. For the event of 20 October 1982, the latent heat release is again shown to be important, whereas the Atlas Mountains orography factor appears to inhibit rainfall. This is the first time that it has been documented that the Atlas-induced modulation of the surface pressure field is not a positive factor for heavy precipitations over eastern Spain. This exceptional case may be due to a negative interaction between the Atlas Mountains and the upper-level dynamics and frontal forcing for this event.

Quantifying Spatiotemporal Variations of Soil Moisture Control on Surface Energy Balance and Near-Surface Air Temperature

Abstract: Soil moisture plays a crucial role for the energy partitioning at Earth’s surface Changing fractions of latent and sensible heat fluxes caused by soil moisture variations can affect both near-surface air temperature and precipitation In this study, a simple framework for the dependence of evaporative fraction (the ratio of latent heat flux over net radiation) on soil moisture is used to analyze spatial and temporal variations of land–atmosphere coupling and its effect on near-surface air temperature Using three different data sources (two reanalysis datasets and one combination of different datasets), three key parameters for the relation between soil moisture and evaporative fraction are estimated: 1) the frequency of occurrence of different soil moisture regimes, 2) the sensitivity of evaporative fraction to soil moisture in the transitional soil moisture regime, and 3) the critical soil moisture value that separates soil moisture- and energy-limited evapotranspiration regimes The results sh

Modelling heat and mass transfer in frozen foods: a review

Abstract: This paper reviews mathematical methods for modelling heat and mass transfer during the freezing, thawing and frozen storage of foods. It starts by considering the problems in modelling heat transfer controlled freezing (the Stefan problem): release of latent heat, sudden changes in thermal conductivity. The author gives a unified overview of the common numerical methods: finite difference, finite element and finite volume. Mass transfer is then considered, involving different phenomena and approaches for dense and porous foods. Supercooling, nucleation and trans-membrane diffusion effects during freezing, and recrystallization during frozen storage are considered next. High pressure thawing and thawing are considered in view of their recent popularity. Finally, the paper offers a brief look at mechanical stresses during freezing, a much neglected area. It is concluded that while modelling heat transferred controlled freezing is a settled problem, much work remains to be done in modelling associated phenomena in order to gain the ability to predict changes in food quality at the micro-level.

Calculating the high-temperature vapour line by Monte Carlo

Abstract: A combination of canonical and grand-canonical ensemble Monte Carlo calculations, together with the virial expansion, have been used to calculate the thermodynamic properties of the liquid/vapour co-existence curve of the (6 : 12) Lennard-Jones fluid for reduced temperatures, [Ttilde] ⩽ 1·1. The results for the liquid density and energy and the latent heat of vaporization are believed to be precise, with the exception of the point at [Ttilde]=1·1 which may lie outside the range of the function fitting the liquid phase Monte Carlo data. The liquid density and the saturated vapour pressure are in very good agreement with the results of perturbation theory. The latent heat of vaporization does not agree well with the experimental data for argon though the fit to liquid density and internal energy is good.