Latent heat

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

Optimizing a process-based ecosystem model with eddy-covariance flux measurements: A pine forest in southern France

Abstract: We design a Bayesian inversion method (gradient-based) to optimize the key functioning parameters of a process-driven land surface model (ORganizing Carbon and Hydrology In Dynamic EcosystEms (ORCHIDEE)) against the combination of prior information upon the parameters and eddy covariance fluxes. The model calculates energy, water, and CO2 fluxes and their interactions on a half-hourly basis, and we carry out the inversion using measurements of CO2, latent heat, and sensible heat fluxes as well as of net radiation over a pine forest in southern France. The inversion method makes it possible to assess the reduction of uncertainties and error correlations of the parameters. We designed an ensemble of inversions with different set ups using flux data over different time periods, in order to (1) identify well-constrained parameters and loosely constrained ones, (2) highlight some model structural deficiencies, and (3) quantify the overall information gained from assimilating each type of CO2 or energy fluxes. The sensitivity of the optimal parameter values to the initial carbon pool sizes and prior parameter values is discussed and an analysis of the posterior uncertainties is performed. Assimilating 3 weeks of half-hourly flux data during the summer improves the fit to diurnal variations, but merely improves the fit to seasonal variations. Assimilating a full year of flux data also improves the fit to the diurnal cycle more than to the seasonal cycle. This points out to the key importance of timescales when inverting parameters from high-frequency eddy-covariance data. We show that photosynthetic parameters such as carboxylation rates are well-constrained by the carbon and water fluxes data and get increased from their prior values, a correction that is corroborated by independent measurements at leaf scale. In contrast, the parameters controlling maintenance, microbial and growth respirations, and their temperature dependencies cannot be robustly determined. The CO2 flux data could not discriminate between the different respiration terms. At face value, all the parameters controlling the surface energy budget can be safely determined, leading to a good model-data fit on different timescales.

Dri-Pc humidity and temperature controller

Abstract: A temperature and humidity control system for natatoriums. The system provides a constant volume of air circulation which is used to control temperature and humidity in the natatorium while inhibiting the accumulation of moisture on the surfaces defining the natatorium. Usually, ambient air is introduced into the system and moisture latent air discharged from the system under controlled conditions. When the humidity of the ambient air is too great the system operates in a self-contained cycle. Return air from the natatorium flowing through the system is treated to maximize its relative humidity. Subsequently, it flows across a cooling coil. This cooled air flows through a heat exchange module where it is placed in exchange relationship with the air being drawn from the natatorium. It cools the air drawn from the natatorium to maximize its relative humidity and this air in turn flows across the refrigeration coil removing substantial quantities of moisture. Combining the refrigeration coil with the heat transfer module and the other components in the system, the sensible/latent heat split is shifted towards higher latent output increasing the overall efficiency of the system as a dehumidification device.

Glacier melt, air temperature and energy balance in different climates: the Bolivian Tropics, the French Alps and northern Sweden

Abstract: [1] This study investigates the physical basis of temperature-index models for three glaciers in contrasting climates: Zongo (16°S, 5050 m, Bolivian Tropics), St Sorlin (45°N, 2760 m, French Alps), and Storglaciaren (67°N, 1370 m, northern Sweden). The daily energy fluxes were computed during melt seasons and correlated with each other and with air temperature on and outside the glacier. The relative contribution of each flux to the correlations between temperature and melt energy was assessed. At Zongo, net short-wave radiation controls the variability of the energy balance and is poorly correlated to temperature. On tropical glaciers, temperature remains low and varies little, melt energy is poorly correlated to temperature, and degree-day models are not appropriate to simulate daily melting. At the yearly scale, the temperature is better correlated to the mass balance because it integrates the ablation and the accumulation processes over a long time period. At Sorlin, the turbulent sensible heat flux is greater because of higher temperatures, but melt variability is still controlled by short-wave radiation. Temperature correlates well with melt energy mainly through short-wave radiation, probably because of diurnal advection of warm air from the valley. At Storglaciaren, high correlations between temperature and melt energy result from substantial variability of the sensible and latent heat fluxes (which both supply energy to the glacier), and their good correlations with temperature. In the three climates, long-wave irradiance is the main source of energy, but its variability is small and poorly correlated to the temperature mainly because cloud emissions dominate its variability.