Radiative Entropy Production Research Articles

Radiative Entropy Production along the Paludification Gradient in the Southern Taiga

Entropy production (σ) is a measure of ecosystem and landscape stability in a changing environment. We calculated the σ in the radiation balance for a well-drained spruce forest, a paludified spruce forest, and a bog in the southern taiga of the European part of Russia using long-term meteorological data. Though radiative σ depends both on surface temperature and absorbed radiation, the radiation effect in boreal ecosystems is much more important than the temperature effect. The dynamic of the incoming solar radiation was the main driver of the diurnal, seasonal, and intra-annual courses of σ for all ecosystems; the difference in ecosystem albedo was the second most important factor, responsible for seven-eighths of the difference in σ between the bog and forest in a warm period. Despite the higher productivity and the complex structure of the well-drained forest, the dynamics and sums of σ in two forests were very similar. Summer droughts had no influence on the albedo and σ efficiency of forests, demonstrating high self-regulation of the taiga forest ecosystems. On the contrary, a decreasing water supply significantly elevated the albedo and lowered the σ in bog. Bogs, being non-steady ecosystems, demonstrate unique thermodynamic behavior, which is fluctuant and strongly dependent on the moisture supply. Paludification of territories may result in increasing instability of the energy balance and entropy production in the landscape of the southern taiga.

The Role of Vegetation on the Ecosystem Radiative Entropy Budget and Trends Along Ecological Succession

Ecosystem entropy production is predicted to increase along ecological succession and approach a state of maximum entropy production, but few studies have bridged the gap between theory and data. Here, we explore radiative entropy production in terrestrial ecosystems using measurements from 64 Free/Fair-Use sites in the FLUXNET database, including a successional chronosequence in the Duke Forest in the southeastern United States. Ecosystem radiative entropy production increased then decreased as succession progressed in the Duke Forest ecosystems, and did not exceed 95% of the calculated empirical maximum entropy production in the FLUXNET study sites. Forest vegetation, especially evergreen needleleaf forests characterized by low shortwave albedo and close coupling to the atmosphere, had a significantly higher ratio of radiative entropy production to the empirical maximum entropy production than did croplands and grasslands. Our results demonstrate that ecosystems approach, but do not reach, maximum entropy production and that the relationship between succession and entropy production depends on vegetation characteristics. Future studies should investigate how natural disturbances and anthropogenic management—especially the tendency to shift vegetation to an earlier successional state—alter energy flux and entropy production at the surface-atmosphere interface.

Radiative entropy balance and vertical stability of a gray atmosphere

Radiative entropy production and entropy flux are subject to ongoing controversial discussion in the scientific literature. The entropy export of planets such as Earth enables and limits all processes of self-organisation in the atmosphere, hydrosphere and biosphere, and is of fundamental importance for climate studies in the context of the so-called greenhouse effect. In this paper, as tutorial examples, formulas for the entropy balance are derived for two simplified gray atmosphere models, each in radiation balance with a black planetary surface of given temperature and with the cold cosmic background. It is shown that the atmospheric entropy production increases strongly with the absorptivity of the atmosphere, while the stationary surface air temperature is always very close to that of the black surface underneath, even though sensible heat flow is intentionally omitted from the models.

Application of the statistical narrow-band correlated-k model to entropy generation through non-grey gas radiation inside a spherical enclosure

In the present work, we proposed a numerical computation of entropy generation by radiative heat transfer through an absorbing-emitting non-grey gas, confined in a spherical enclosure. The 'Ray Tracing' method is associated to the statistical narrow band correlated-k SNBCK model, to solve the radiative transfer equation and to deduce the radiative properties of the gas. The effects of boundary conditions, enclosure dimensions and spectral correlation on the entropy generation are presented. The results show that the volumetric radiative entropy production is more developed in heating configuration while the wall radiative entropy production is more developed in case of cooling.

Greenhouse gases and climatic states of minimum entropy production

The hypothesis of minimum entropy production is applied to a simple one‐dimensional energy balance model and is analyzed for different values of the radiative forcing due to greenhouse gases. The extremum principle is used to determine the planetary “conductivity” and to avoid the “diffusive” approximation, which is commonly assumed in this type of model. For present conditions the result at minimum radiative entropy production is similar to that obtained by applying the classical model. Other climatic scenarios show visible differences, with better behavior for the extremal case.

Radiative entropy production—lost heat into entropy

Heat flow δQ of the First Law of Thermodynamics is expressed in terms of the entropy flow δ( Q/ T) δQ  δ[ T( Q/ T)] = Tδ( Q/ T)+( Q/ T) dT where Tδ( Q/ T) denotes the energy equivalent of the entropy flow, and ( Q/ T) dT introduces the concept of lost heat into entropy production. Here Q = Q K + Q R where superscripts K and R indicate conduction and radiation, respectively. In terms of the lost heat, dimensionless entropy productions on the wall of a thermal boundary layer and in a quenched laminar flame are respectively shown to be П x ~ (1+q x R/q x K)Nu x 2 and П s ~ (1+q R/q K)Pe −2 where q R and q K are the one-dimensional fluxes associated with Q R and Q K , Nu x is a local Nusselt number, and Pe is a Peclet number based on the laminar flame speed at the adiabatic flame temperature. The tangency condition, ∂Pe/ ∂T b = 0, customarily used in the evaluation of minimum quench distance without any physical justification, is shown to correspond to an extremum in entropy production.

Radiative entropy production

THE radiative tensor obtained from the specular moments of the transfer equation is considered. The radiative entropy production is expressed in terms of this tensor. Contents The theory of gas radiation dates back to studies Rayleigh made over a century ago on the illumination and polarization of the sunlit sky. Since then, the theory has rapidly grown because of the efforts of astrophysicis ts and later of applied scientists and engineers. However, the entropy production associated with radiation apparently remains untreated and is the motivation of this study. As is well known, the entropy production results from dissipative processes (involving mass, species, momentum, and/or heat transfer and electromagnetic or nuclear transport). Less known is the fact that the dissipation may have a diffusive or hysteretic origin, the diffusion being directional and the hysteresis being cyclic. However, except for a few cases (such as strain hardening and the magnetic saturation), the majority of dissipative processes (including the dissipation of radiation) are of diffusive nature. A recent study by Arpaci 1 shows, in terms of the radiative stress obtained from the specular (kinetic) moments of the transfer equation, the diffusive nature of radiation for any optical thickness. Accordingly, the expression to be developed for entropy production is in terms of this stress and includes also the dissipation resulting from the conduction of heat and viscous friction. First, some remarks on the radiative stress are needed. These will be made in terms of spectrally averaged radiation because of its simplicity. A monochromatic approach, which may be needed for a quantitative study, is not essential here because of the conceptual nature of the intended study. As pointed out by Felske and Tien,2 there are a variety of practical situations in which scattering is not important. For these situations, consider the spectrally averaged transfer equation,