474 research outputs found
Comprehending environmental and economic sustainability: Comparative analysis of stability principles in the biosphere and free market economy
Using the formalism of Lyapunov potential function it is shown that the
stability principles for biomass in the ecosystem and for employment in
economics are mathematically similar. The ecosystem is found to have a stable
and an unstable stationary state with high (forest) and low (grasslands)
biomass, respectively. In economics, there is a stable stationary state with
high employment, which corresponds to mass production of conventional goods
sold at low cost price, and an unstable stationary state with lower employment,
which corresponds to production of novel goods appearing in the course of
technological progress. An additional stable stationary state is described for
economics, the one corresponding to very low employment in production of life
essentials such as energy and raw materials. In this state the civilization
currently pays 10% of global GDP for energy produced by a negligible minority
of the working population (currently ~0.2%) and sold at prices greatly
exceeding the cost price by 40 times. It is shown that economic ownership over
energy sources is equivalent to equating measurable variables of different
dimensions (stores and fluxes), which leads to effective violation of the laws
of energy and matter conservation.Comment: 51 pages, 6 figure
Dissipative heat engine is thermodynamically inconsistent
A heat engine operating on the basis of the Carnot cycle is considered, where
the mechanical work performed is dissipated within the engine at the
temperature of the warmer isotherm and the resulting heat is added to the
engine together with an external heat input. The resulting work performed by
the engine per cycle is increased at the expense of dissipated work produced in
the previous cycle. It is shown that such a dissipative heat engine is
thermodynamically inconsistent violating the first and second laws of
thermodynamics. The existing physical models employing the dissipative heat
engine concept, in particular, the heat engine model of hurricane development,
are physically invalid.Comment: 9 pages, 2 figure
The key physical parameters governing frictional dissipation in a precipitating atmosphere
Precipitation generates small-scale turbulent air flows the energy of which
ultimately dissipates to heat. The power of this process has previously been
estimated to be around 2-4 W m-2 in the tropics: a value comparable in
magnitude to the dynamic power of the global circulation. Here we suggest that
this previous power estimate is approximately double the true figure. Our
result reflects a revised evaluation of the mean precipitation path length Hp.
We investigate the dependence of Hp on surface temperature,relative
humidity,temperature lapse rate and degree of condensation in the ascending
air. We find that the degree of condensation,defined as the relative change of
the saturated water vapor mixing ratio in the region of condensation, is a
major factor determining Hp. We estimate from theory that the mean large-scale
rate of frictional dissipation associated with total precipitation in the
tropics lies between 1 and 2 W m-2 and show that our estimate is supported by
empirical evidence. We show that under terrestrial conditions frictional
dissipation constitutes a minor fraction of the dynamic power of
condensation-induced atmospheric circulation,which is estimated to be at least
2.5 times larger. However,because Hp increases with surface temperature Ts, the
rate of frictional dissipation would exceed that of condensation-induced
dynamics, and thus block major circulation, at Ts >~320 K in a moist adiabatic
atmosphere.Comment: 12 pp, 2 figure
Condensation of water vapor in the gravitational field
Physical peculiarities of water vapor condensation under conditions of
hydrostatic equilibrium are considered. The power of stationary dynamic air
fluxes and the vertical temperature distribution caused by condensation on
large horizontal scales are estimated.Comment: 10 p
Where do winds come from? A new theory on how water vapor condensation influences atmospheric pressure and dynamics
Phase transitions of atmospheric water play a ubiquitous role in the Earth's
climate system, but their direct impact on atmospheric dynamics has escaped
wide attention. Here we examine and advance a theory as to how condensation
influences atmospheric pressure through the mass removal of water from the gas
phase with a simultaneous account of the latent heat release. Building from the
fundamental physical principles we show that condensation is associated with a
decline in air pressure in the lower atmosphere. This decline occurs up to a
certain height, which ranges from 3 to 4 km for surface temperatures from 10 to
30 deg C. We then estimate the horizontal pressure differences associated with
water vapor condensation and find that these are comparable in magnitude with
the pressure differences driving observed circulation patterns. The water vapor
delivered to the atmosphere via evaporation represents a store of potential
energy available to accelerate air and thus drive winds. Our estimates suggest
that the global mean power at which this potential energy is released by
condensation is around one per cent of the global solar power -- this is
similar to the known stationary dissipative power of general atmospheric
circulation. We conclude that condensation and evaporation merit attention as
major, if previously overlooked, factors in driving atmospheric dynamics
Greenhouse effect dependence on atmospheric concentrations of greenhouse substances and the nature of climate stability on Earth
International audienceDue to the exponential positive feedback between sea surface temperature and saturated water vapour concentration, dependence of the planetary greenhouse effect on atmospheric water content is critical for stability of a climate with extensive liquid hydrosphere. In this paper on the basis of the law of energy conservation we develop a simple physically transparent approach to description of radiative transfer in an atmosphere containing greenhouse substances. It is shown that the analytical solution of the equation thus derived coincides with the exact solution of the well-known radiative transfer equation to the accuracy of 20% for all values of atmospheric optical depth. The derived equation makes it possible to easily take into account the non-radiative thermal fluxes (convection and latent heat) and obtain an analytical dependence of the greenhouse effect on atmospheric concentrations of a set of greenhouse substances with arbitrary absorption intervals. The established dependence is used to analyse stability of the modern climate of Earth. It is shown that the modern value of global mean surface temperature, which corresponds to the liquid state of the terrestrial hydrosphere, is physically unstable. The observed stability of modern climate over geological timescales is therefore likely to be due to dynamic singularities in the physical temperature-dependent behaviour of the greenhouse effect. We hypothesise that such singularities may appear due to controlling functioning of the natural global biota and discuss major arguments in support of this conclusion
A critical analysis of the assumptions underlying the formulation of maximum potential intensity for tropical cyclones
Emanuel's concept of maximum potential intensity (E-PI) estimates the maximum
velocity of tropical cyclones from environmental parameters assuming thermal
wind (gradient-wind and hydrostatic balances) and slantwise neutrality in the
free troposphere. E-PI's key equation relates proportionally the radial
gradients of saturated moist entropy and angular momentum. Here the E-PI
derivation is reconsidered to show that the thermal wind and slantwise
neutrality imply zero radial gradients of saturation entropy and angular
momentum at an altitude where, for a given radius, the tangential wind has a
maximum. It is further shown that, while E-PI's key equation requires that, at
the point of maximum tangential wind, the air temperature must increase towards
the storm center, the thermal wind equation dictates the opposite. From the
analysis of the equations of motion at the altitude of maximum tangential wind
in the free troposphere, it is concluded that here the air flow must be
supergradient. This implies that the supergradiency factor (a measure of the
gradient-wind imbalance) must change in the free troposphere as the air flow
tends to restore the balance. It is shown that such a change modifies the
derivative of saturation entropy over angular momentum, which cannot therefore
remain constant in the free troposphere as E-PI requires. The implications of
these findings for the internal coherence of E-PI, including its boundary layer
closure, are discussed.Comment: Revised for JAS. Reply to three reviewers can be found in appendix C.
25 pages, 1 figur
Biotic pump of atmospheric moisture as driver of the hydrological cycle on land
In this paper the basic geophysical and ecological principles are jointly analyzed that allow the landmasses of Earth to remain moistened sufficiently for terrestrial life to be possible. 1. Under gravity, land inevitably loses water to the ocean. To keep land moistened, the gravitational water runoff must be continuously compensated by the atmospheric ocean-to-land moisture transport. Using data for five terrestrial transects of the International Geosphere Biosphere Program we show that the mean distance to which air fluxes can transport moisture over non-forested areas, does not exceed several hundred kilometers; precipitation decreases exponentially with distance from the ocean. 2. In contrast, precipitation over extensive natural forests does not depend on the distance from the ocean along several thousand kilometers, as illustrated for the Amazon and Yenisey river basins and Equatorial Africa. This points to the existence of an active biotic pump transporting atmospheric moisture inland from the ocean. 3. Physical principles of the biotic moisture pump are investigated based on the previously unstudied properties of atmospheric water vapor, which can be either in or out of aerostatic equilibrium depending on the lapse rate of air temperature. A novel physical principle is formulated according to which the low-level air moves from areas with weak evaporation to areas with more intensive evaporation. Due to the high leaf area index, natural forests maintain high evaporation fluxes, which support the ascending air motion over the forest and "suck in" moist air from the ocean, which is the essence of the biotic pump of atmospheric moisture. In the result, the gravitational runoff water losses from the optimally moistened forest soil can be fully compensated by the biotically enhanced precipitation at any distance from the ocean. 4. It is discussed how a continent-scale biotic water pump mechanism could be produced by natural selection acting on individual trees. 5. Replacement of the natural forest cover by a low leaf index vegetation leads to an up to tenfold reduction in the mean continental precipitation and runoff, in contrast to the previously available estimates made without accounting for the biotic moisture pump. The analyzed body of evidence testifies that the long-term stability of an intense terrestrial water cycle is unachievable without the recovery of natural, self-sustaining forests on continent-wide areas
Comment on "The Tropospheric Land-Sea Warming Contrast as the Driver of Tropical Sea Level Pressure Changes" by Bayr and Dommenget
T Bayr and D Dommenget [J. Climate 26 (2013) 1387] proposed a model of
temperature-driven air redistribution to quantify the ratio between changes of
sea level pressure and mean tropospheric temperature in the
tropics. This model assumes that the height of the tropical troposphere is
isobaric. Here problems with this model are identified. A revised relationship
between and is derived governed by two parameters -- the isobaric
and isothermal heights -- rather than just one. Further insight is provided by
the model of R S Lindzen and S Nigam [J. Atmos. Sci. 44 (1987) 2418], which was
the first to use the concept of isobaric height to relate tropical to air
temperature, and did this by assuming that isobaric height is always around 3
km and isothermal height is likewise near constant. Observational data,
presented here, show that neither of these heights is spatially universal nor
do their mean values match previous assumptions. Analyses show that the ratio
of the long-term changes in and associated with land-sea
temperature contrasts in a warming climate -- the focus of Bayr and Dommenget
[2013] -- is in fact determined by the corresponding ratio of spatial
differences in the annual mean and . The latter ratio, reflecting
lower pressure at higher temperature in the tropics, is dominated by meridional
pressure and temperature differences rather than by land-sea contrasts.
Considerations of isobaric heights are shown to be unable to predict either
spatial or temporal variation in . As noted by Bayr and Dommenget [2013],
the role of moisture dynamics in generating sea level pressure variation
remains in need of further theoretical investigations.Comment: 26 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1404.101
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