One-dimensional Climate Model Research Articles

Effects of Varying Saturation Vapor Pressure on Climate, Clouds, and Convection

Abstract We investigate how climate, clouds, and convection change as the amount of water vapor in the atmosphere is varied by altering the saturation vapor pressure (SVP) by a constant in a one-dimensional climate model. We identify four effects of altering SVP on clouds in an Earthlike climate with distinct layers of low and high clouds. First, the anvils of high clouds get higher as SVP is increased (and vice versa) because they are bound by radiative constraints to occur at a lower temperature. The vapor pressure path above the cold anvils does not change in Earthlike climates. Second, low clouds get lower as SVP increases (and vice versa) because they are coupled to a convective boundary layer (CBL) that shallows primarily from an increase in the tropospheric static stability. The third and fourth effects follow from the first two, namely, that single-layer cloud states exist both in vapor-poor states with a merged cloud deck and vapor-rich states with an elevated cloud deck. We identify two cloud instability parameters that determine the transitions between single- and double-layer cloud regimes. Qualitatively, sufficiently vapor-poor states have a deep, diffusive layer that overlaps with a weaker convective layer (topping out at the tropopause) that cannot maintain low relative humidity in the midtroposphere through the drying of descending air, thus causing the cloud layers to merge. Sufficiently vapor-rich states lose their low clouds as the shallowing CBL drops below the lifting condensation level.

Experimental study of sediment transport processes by liquid water and brine under Martian pressure

We present here an experimental study to compare the behaviour of water and brine releases over loose sediments under present-day Martian pressure. Water has been invoked to explain current or past Martian surface features for decades. Recent studies have indicated that current surface conditions are, in certain times and places, compatible with the transient existence of liquid water or brine. However, the behaviour of water or brine releases over loose sediments under low Martian atmospheric pressure has been poorly studied.We performed 33 experiments of water and brine (MgSO4 at 19 wt%) releases over sandy slopes of various temperatures (0 °C to 20 °C), in a chamber allowing the reproduction of Martian pressure 6–7 millibars (mbar). We observe sediment transport mechanisms, that do not occur on Earth, caused by the boiling of water or brine at Martian pressures: grain ejection and “levitation” of sand pellets on cushions of vapour. The main parameter controlling the behaviour of the flow is the temperature of the substrate. Water and brine flows transport similar volumes of sediment under Martian pressure. We show that the grain ejection is the most efficient transport mechanism, dominating the volumes of sediment transported. Pellet “levitation” should lead to longer features formed with brine than with pure water on Mars. Boiling induced sediment transport requires much less water than sediment transport by overland flow to form morphologies similar in size or volume. Moreover, our one-dimensional climate model runs reveal that the temperatures at which we observe those types of transport are predicted to occur at the Martian surface today and in the past. When scaled to Mars, the morphologies we observe with water and brine experiments should be resolvable using the High-Resolution Science Experiment (HiRISE) camera at ∼25 cm/pix. Overall, our results show that boiling must be taken into account when considering sediment-rich flows under recent or current Martian conditions.

PICASO 3.0: A One-dimensional Climate Model for Giant Planets and Brown Dwarfs

Upcoming James Webb Space Telescope observations will allow us to study exoplanet and brown dwarf atmospheres in great detail. The physical interpretation of these upcoming high signal-to-noise observations requires precise atmospheric models of exoplanets and brown dwarfs. While several 1D and 3D atmospheric models have been developed in the past three decades, these models have often relied on simplified assumptions like chemical equilibrium and are also often not open-source, which limits their usage and development by the wider community. We present a Python-based 1Dl atmospheric radiative-convective equilibrium (RCE) model. This model has heritage from the Fortran-based code, which has been widely used to model the atmospheres of solar system objects, brown dwarfs, and exoplanets. In short, the basic capability of the original model is to compute the atmospheric state of the object under RCE given its effective or internal temperature, gravity, and host-star properties (if relevant). In the new model, which has been included within the well-utilized code-base PICASO, we have added these original features as well as the new capability of self-consistently treating disequilibrium chemistry. This code is widely applicable to hydrogen-dominated atmospheres (e.g., brown dwarfs and giant planets).

Fuel Cell Hybrid-Electric Aircraft: Design, Operational, and Environmental Impact

To reduce the environmental footprint of the aviation industry, aircraft with new propulsion systems are increasingly under consideration. In this paper, the potential of a fuel cell hybrid-electric aircraft (FCHEA) powered by hydrogen and kerosene is assessed. First, the methodology for the conceptual design of a single-aisle short-range FCHEA is developed and presented. Then, the environmental impact of this aircraft on its design mission is determined by means of a one-dimensional climate model and the climate metric sustained global temperature potential with a time horizon of 100 years. To complete the picture, the fleet adoption of the FCHEA concept is determined with the help of a fleet system dynamics model taking future air traffic development, fleet age, and production capacities into account. This makes it possible to analyze the potential of FCHEA to improve the environmental footprint of aviation considering the operational environment in the global aviation market. The results show that for a single FCHEA powered by liquid hydrogen produced via electrolysis with renewable energies, climate impact reductions of 15.2–17.8% can be achieved. The fleet uptake of the FCHEA made full use of the available production capacities, but still it was able to serve only 15.8% of total available seat kilometers.

Can increased atmospheric CO2 levels trigger a runaway greenhouse?

Recent one-dimensional (globally averaged) climate model calculations by Goldblatt et al. (2013) suggest that increased atmospheric CO(2) could conceivably trigger a runaway greenhouse on present Earth if CO(2) concentrations were approximately 100 times higher than they are today. The new prediction runs contrary to previous calculations by Kasting and Ackerman (1986), which indicated that CO(2) increases could not trigger a runaway, even at Venus-like CO(2) concentrations. Goldblatt et al. argued that this different behavior is a consequence of updated absorption coefficients for H(2)O that make a runaway more likely. Here, we use a 1-D climate model with similar, up-to-date absorption coefficients, but employ a different methodology, to show that the older result is probably still valid, although our model nearly runs away at ∼12 preindustrial atmospheric levels of CO(2) when we use the most alarmist assumptions possible. However, we argue that Earth's real climate is probably stable given more realistic assumptions, although 3-D climate models will be required to verify this result. Potential CO(2) increases from fossil fuel burning are somewhat smaller than this, 10-fold or less, but such increases could still cause sufficient warming to make much of the planet uninhabitable by humans.

Warming early Mars with CO2 and H2

The presence of valleys on ancient terrains of Mars suggest that liquid water flowed on the martian surface 3.8 billion years ago or before. The above-freezing temperatures required to explain valley formation could have been transient, in response to frequent large meteorite impacts on early Mars, or they could have been caused by long-lived greenhouse warming. Climate models that consider only the greenhouse gases carbon dioxide and water vapor have been unable to recreate warm surface conditions, given the lower solar luminosity at that time. Here we use a one-dimensional climate model to demonstrate that an atmosphere containing 1.3-4 bar of CO2 and water vapor, along with 5 to 20 percent H2, could have raised the mean surface temperature of early Mars above the freezing point of water. Vigorous volcanic outgassing from a highly reduced early martian mantle is expected to provide sufficient atmospheric H2 and CO2, the latter from the photochemical oxidation of outgassed CH4 and CO, to form a CO2-H2 greenhouse. Such a dense early martian atmosphere is consistent with independent estimates of surface pressure based on cratering data.

On the possible contribution of solar-cosmic factors to the global warming of XX century

The effect of changes in the total solar irradiance and intensity of galactic cosmic rays on the increase in the global temperature of the Earth over the last 120 years was investigated using a one-dimensional energy-balance climate model. It is shown that the joint effect of solar and cosmic factors during this periodcan lead to an increase in the average temperature of the northern hemisphere by 0.25–0.35°C. It is concluded that the solar luminosity and the cosmic-ray flux can make a significant contribution to the global warming of the last century.

Earth rings for planetary environment control

An artificial planetary ring about the Earth, composed of passive particles or controlled spacecraft with parasols, is proposed to reduce global warming. A flat ring from 1.2 to 1.6 Earth radii would shade mainly the tropics, moderating climate extremes, and counteract global warming. A preliminary design of the ring is developed, and a one-dimensional climate model is used to evaluate its performance. Earth, lunar, and asteroidal material sources are compared to determine the costs of the particle ring and the spacecraft ring. Environmental concerns and effects on existing satellites in Earth orbit are addressed. The particle ring endangers LEO satellites, is limited to cooling only, and lights the night many times as bright as the full moon. It would cost an estimated $6–200 trillion. The ring of controlled satellites with reflectors has other attractive uses, and would cost an estimated $125–500 billion.

Euler–Lagrange equation of the most simple 1-D climate model based on the maximum entropy production hypothesis

A simple one-dimensional (1-D) climate model in the meridional direction is considered based on the maximum entropy production hypothesis. This model calculates latitudinal distribution of the emitted long-wave radiation and meridional heat transport for a given latitudinal distribution of the absorbed solar radiation. By treating the problem analytically, an Euler–Lagrange equation and a numerical method solving it are obtained. Calculations based on the maximum entropy production hypothesis qualitatively explain an enhancement of the poleward heat transport observed in a last glacial maximum simulation with a coupled general-circulation model. Copyright © 2005 Royal Meteorological Society

Eddy Heat Diffusivity at Maximum Dissipation in a Radiative-convective One-dimensional Climate Model

The hypothesis that the steady state of the climate is constrained to maximize its dissipation is investigated by using a one-dimensional radiative-convective model where the convective fluxes are parameterized following the mixing length theory. The eddy heat diffusivity is chosen to produce the maximum energy dissipation caused by convection (maximum dissipation principle). The state of maximum dissipation due to heat diffusion in a model atmosphere with a fixed vertical profile of specific humidity is obtained for a value of the eddy heat diffusivity, which is in close agreement with that expected for air in stirred conditions. By including the temperature—opacity feedback (i.e., condensable absorbing gas in the infrared with a fixed vertical profile of relative humidity), the state of maximum dissipation is attained for a value of the eddy heat diffusivity that lies within the range of the expected values. In this case, the vertical temperature profile is convectively stable and does not differ in excess from the observed one. Thus, it is suggested that the results here reported represent an ‘empirical’ support to the maximum dissipation principle.

Modelling solar energy input in greenhouses

A semi one-dimensional climate model was used to investigate the relative importance of the constructional parameters that influence the solar energy collecting efficiency of greenhouses under Western European conditions. Parameters investigated were the transmittance of the greenhouse frame, the radiometric properties of the greenhouse cladding and the floor, as well as the type of condensation (as a film or as drops). Their effect on the auxiliary heating requirements and the several solar energy fluxes in the greenhouse were simulated for a year-round tomato crop. The results pointed out that greenhouses catch about two thirds of the solar radiation available. This rather poor efficiency is due to the fact that greenhouses are fixed constructions, so their efficiency highly depends on their position and geometry, which are mainly determined by horticultural constraints. Most of the solar energy entering the greenhouse was found to be absorbed by the vegetation. Auxiliary heating requirements were hardly influenced by changes of the frame or cladding transmittances, although the transmittance reduction caused by condensation as hemispherical drops caused a 2.8% increase of the energy demand. The floor characteristics had an impact on the greenhouse energy demand and on the amount of solar energy available to the canopy, only for small plants on an almost uncovered floor.

Entropy Production In Thermodynamic Climate Models

We present a non-equilibrium theory in a system with heat and radiative fluxes. The obtained expression for the entropy production is applied to a simple one-dimensional climate model based on the first law of thermodynamics. In the model, the dissipative fluxes are assumed to be independent variables, following the criteria of the Extended Irreversible Thermodynamics (BIT) that enlarges, in reference to the classical expression, the applicability of a macroscopic thermodynamic theory for systems far from equilibrium. We analyze the second differential of the classical and the generalized entropy as a criteria of stability of the steady states. Finally, the extreme state is obtained using variational techniques and observing that the system is close to the maximum dissipation rate.

Atmospheric carbon dioxide concentrations before 2.2 billion years ago.

The composition of the Earth's early atmosphere is a subject of continuing debate. In particular, it has been suggested that elevated concentrations of atmospheric carbon dioxide would have been necessary to maintain normal surface temperatures in the face of lower solar luminosity in early Earth history. Fossil weathering profiles, known as palaeosols, have provided semi-quantitative constraints on atmospheric oxygen partial pressure (pO2) before 2.2 Gyr ago. Here we use the same well studied palaeosols to constrain atmospheric pCO2 between 2.75 and 2.2 Gyr ago. The observation that iron lost from the tops of these profiles was reprecipitated lower down as iron silicate minerals, rather than as iron carbonate, indicates that atmospheric pCO2 must have been less than 10(-1.4) atm--about 100 times today's level of 360 p.p.m., and at least five times lower than that required in one-dimensional climate models to compensate for lower solar luminosity at 2.75 Gyr. Our results suggest that either the Earth's early climate was much more sensitive to increases in pCO2 than has been thought, or that one or more greenhouse gases other than CO2 contributed significantly to the atmosphere's radiative balance during the late Archaean and early Proterozoic eons.

The Implementation and Validation of Improved Land-Surface Hydrology in an Atmospheric General Circulation Model

New land-surface hydrologic parameterizations are implemented into the NASA Goddard Institute for Space Studies (GISS) General Circulation Model (GCM). These parameterizations are: 1) runoff and evapotranspiration functions that include the effects of subgrid-scale spatial variability and use physically based equations of hydrologic flux at the soil surface and 2) a realistic soil moisture diffusion scheme for the movement of water and root sink in the soil column. A one-dimensional climate model with a complete hydrologic cycle is used to screen the basic sensitivities of the hydrological parameterizations before implementation into the full three-dimensional GCM. Results of the final simulation with the GISS GCM and the new land-surface hydrology indicate that the runoff rate, especially in the tropics, is significantly improved. As a result, the remaining components of the heat and moisture balance show similar improvements when compared to observations. The validation of model results is carried from the large global (ocean and land-surface) scale to the zonal, continental, and finally the regional river basin scales.

Habitable Zones around Main Sequence Stars

A one-dimensional climate model is used to estimate the width of the habitable zone (HZ) around our Sun and around other main sequence stars. Our basic premise is that we are dealing with Earth-like planets with CO2/H2O/N2 atmospheres and that habitability requires the presence of liquid water on the planet's surface. The inner edge of the HZ is determined in our model by loss of water via photolysis and hydrogen escape. The outer edge of the HZ is determined by the formation of CO2 clouds, which cool a planet's surface by increasing its albedo and by lowering the convective lapse rate. Conservative estimates for these distances in our own Solar System are 0.95 and 1.37 AU, respectively; the actual width of the present HZ could be much greater. Between these two limits, climate stability is ensured by a feedback mechanism in which atmospheric CO2 concentrations vary inversely with planetary surface temperature. The width of the HZ is slightly greater for planets that are larger than Earth and for planets which have higher N2 partial pressures. The HZ evolves outward in time because the Sun increases in luminosity as it ages. A conservative estimate for the width of the 4.6-Gyr continuously habitable zone (CHZ) is 0.95 to 1.15 AU.Stars later than F0 have main sequence lifetimes exceeding 2 Gyr and, so, are also potential candidates for harboring habitable planets. The HZ around an F star is larger and occurs farther out than for our Sun; the HZ around K and M stars is smaller and occurs farther in. Nevertheless, the widths of all of these HZs are approximately the same if distance is expressed on a logarithmic scale. A log distance scale is probably the appropriate scale for this problem because the planets in our own Solar System are spaced logarithmically and because the distance at which another star would be expected to form planets should be related to the star's mass. The width of the CHZ around other stars depends on the time that a planet is required to remain habitable and on whether a planet that is initially frozen can be thawed by modest increases in stellar luminosity. For a specified period of habitability, CHZs around K and M stars are wider (in log distance) than for our Sun because these stars evolve more slowly. Planets orbiting late K stars and M stars may not be habitable, however, because they can become trapped in synchronous rotation as a consequence of tidal damping. F stars have narrower (log distance) CHZ's than our Sun because they evolve more rapidly. Our results suggest that mid-to-early K stars should be considered along with G stars as optimal candidates in the search for extraterrestrial life.

Delayed Albedo Effects in a Zero-Dimensional Climate Model

Abstract A globally averaged radiative energy-balance model incorporating a time-delayed albedo has been investigated. The parameterization of the albedo in terms of the average global temperature is furthermore not monotonic since it incorporates a “link.” This irregularity is assumed to occur for a temperature range wherein the general circulation states of the atmosphere are associated with a high degree of cloud cover, i.e., a large albedo. The fundamental stability properties of the governing delay-differential equation have been resolved using analytical techniques. Numerical investigations have revealed that this simple model does justice to many of the qualitative features generally associated with more complex one-dimensional climate models. Hence it is capable of demonstrating auto-oscillatory behavior as well as a sequence of period-doubling bifurcations towards chaos.

Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus

A one-dimensional climate model is used to study the response of an Earth-like atmosphere to large increases in solar flux. For fully saturated, cloud-free conditions, the critical solar flux at which a runaway greenhouse occurs, that is, the oceans evaporate entirely, is found to be 1.4 times the present flux at Earth's orbit ( S 0). This value is close to the flux expected at Venus' orbit early in solar system history. It is nearly independent of the amount of CO 2 present in the atmosphere, but is sensitive to the H 2O absorption coefficient in the 8- to 12-μm window region. Clouds should tend to depress the surface temperature on a warm, moist planet; thus, Venus may originally have had oceans if its initial water endowment was close to that of Earth. It lost them early in its history, however, because of rapid photodissociation of water vapor followed by escape of hydrogen to space. The critical solar flux above which water is rapidly lost could be as low as 1.1 S 0. The surface temperature of a runaway greenhouse atmosphere containing a full ocean's worth of water would have been in excess of 1500°K—above the solidus for silicate rocks. The presence of such a steam atmosphere during accretion may have significantly influenced the early thermal evolution of both Earth and Venus.

Light enhancement in greenhouses using prismatic refractors in a Venetian blind assembly

A semi one-dimensional climate model was used to investigate the relative importance of the constructional parameters that influence the solar energy collecting efficiency of greenhouses under Western European conditions. Parameters investigated were the transmittance of the greenhouse frame, the radiometric properties of the greenhouse cladding and the floor, as well as the type of condensation (as a film or as drops). Their effect on the auxiliary heating requirements and the several solar energy fluxes in the greenhouse were simulated for a year-round tomato crop. The results pointed out that greenhouses catch about two thirds of the solar radiation available. This rather poor efficiency is due to the fact that greenhouses are fixed constructions, so their efficiency highly depends on their position and geometry, which are mainly determined by horticultural constraints. Most of the solar energy entering the greenhouse was found to be absorbed by the vegetation. Auxiliary heating requirements were hardly influenced by changes of the frame or cladding transmittances, although the transmittance reduction caused by condensation as hemispherical drops caused a 2.8% increase of the energy demand. The floor characteristics had an impact on the greenhouse energy demand and on the amount of solar energy available to the canopy, only for small plants on an almost uncovered floor.

Interactive Cloud Formation and Climatic Temperature Perturbations

Abstract A one-dimensional climate model with an interactive cloud formation program is developed to investigate its effects on temperature perturbations due to various radiative forcings including doubling of CO2, a 2% increase of the solar constant and the increase of the cirrus IR emissivity. By virtue of the K-theory for turbulence transfer of sensible and latent heat flux we demonstrate that the model may be described by a set of partial differential equations governing the thermodynamic energy balance, water vapor transport, vertical velocity in the cloudy region and cloud cover. In particular, we illustrate that the climatic temperature perturbation experiment may be carried out as a boundary value problem. Moreover, in order to effectively incorporate interactive cloud formation and radiative transfer programs in the model, we have designed a cloud compaction scheme based on statistical and stochastic procedures for the estimate of cloud covers, thicknesses, heights and positions for high, middle ...

Parameterization of meridional energy flux in a one-dimensional climate model

The zonally averaged meridional energy transport is parameterized in terms of the zonally averaged temperature gradient and its radiative equilibrium value. Two climate regimes are identified: radiative equilibrium and isothermal climates. The transport and temperature gradient are intermediate between corresponding quantities of these two climates. The parameterization assumes a linear increase of transport as temperature gradient departs from its radiative equilibrium value. The parameterization is formulated using a one-dimensional climate model. Ice-albedo feedback provides the mechanism for climate changes. The parameterization works well for climates associated with seasonal changes.