Radiative transfer

About: Radiative transfer is a research topic. Over the lifetime, 43287 publications have been published within this topic receiving 1176539 citations.

Atlantic Air-Sea Interaction

Abstract: Publisher Summary This article is concerned with the causes of the variations in the surface temperature of the Atlantic Ocean from year to year and over longer periods. The processes, which influence the ocean temperature, are partly radiative transfers, partly heat exchange at the interface of ocean and atmosphere, and partly advective heat transfers by the ocean currents. The net radiative heat balance of the ocean is influenced by possible variations of the solar radiative output, and by the transmissivity of the atmosphere for short- and long-wave radiation. Variations in cloudiness would be the factor, most likely to influence measurably the annual radiative heat budget of the ocean. The ocean currents provide important contributions to the local heat budget, positive in the warm currents and negative in the cold currents. The changes in intensity of the oceanic circulation are mainly dictated by changes in the atmospheric circulation, and the resulting changes in the temperature field of the ocean surface must in turn, influence the thermodynamics of the atmospheric circulation. A clarification of these relationships is a prerequisite for the understanding of the mechanism of climatic change. This article will present some empirical findings, which have a bearing on those problems. Before proceeding to display the empirical findings on the large-scale ocean–atmosphere interaction, a brief outline will be given of the theories on the meteorological control of ocean currents and on the interface heat transfers.

Gold nanoparticles quench fluorescence by phase induced radiative rate suppression.

Abstract: The fluorescence quantum yield of Cy5 molecules attached to gold nanoparticles via ssDNA spacers is measured for Cy5-nanoparticle distances between 2 and 16 nm. Different numbers of ssDNA per nanoparticle allow to fine-tune the distance. The change of the radiative and nonradiative molecular decay rates with distance is determined using time-resolved photoluminescence spectroscopy. Remarkably, the distance dependent quantum efficiency is almost exclusively governed by the radiative rate.

Population Diagram Analysis of Molecular Line Emission

Abstract: We develop the use of the population diagram method to analyze molecular emission in order to derive physical properties of interstellar clouds. We focus particular attention on how the optical depth affects the derived total column density and the temperature. We derive an optical depth correction factor that can be evaluated based on observations and that incorporates the effect of saturation on derived upper level populations. We present analytic results for linear molecules in local thermodynamic equilibrium (LTE). We investigate numerically how subthermal excitation influences the population diagram technique, studying how the determination of kinetic temperature is affected when the local density is insufficient to achieve LTE. We present results for HC3N and CH3OH, representative of linear and nonlinear molecules, respectively. In some cases, alternative interpretations to the standard optically thin and thermalized picture yield significantly different results for column density and kinetic temperature, and we discuss this behavior. The population diagram method can be a very powerful tool for determining physical conditions in dense clouds if proper recognition is given to effects of saturation and subthermal excitation. We argue that the population diagram technique is, in fact, superior to fitting intensities of different transitions directly, and we indicate how it can be effectively employed.