One-dimensional Radiative-convective Model Research Articles

The Role of Convective Model Choice in Calculating the Climate Impact of Doubling CO2

The role of the parameterization of vertical convection in calculating the climate impact of doubling CO2 is assessed using both one-dimensional radiative-convective vertical models and in the latitude-dependent Hadley-baroclinic model of Lindzen and Farrell (1980). Both the conventional 6.5 K/km and the moist-adiabat adjustments are compared with a physically-based, cumulus-type parameterization. The model with parameterized cumulus convection has much less sensitivity than the 6.5 K/km adjustment model at low latitudes, a result that can be to some extent imitiated by the moist-adiabat adjustment model. However, when averaged over the globe, the use of the cumulus-type parameterization in a climate model reduces sensitivity only approximately 34% relative to models using 6.5 K/km convective adjustment. Interestingly, the use of the cumulus-type parameterization appears to eliminate the possibility of a runaway greenhouse.

Properties of dust in the martian atmosphere and its effect on temperature structure

Data from the Viking lander imaging experiment and the IRIS experiment on board the Mariner 9 Orbiter are used to develop a one-dimensional radiative-convective model to describe the Mars temperature profile. Photography was employed to determine the optical depth, mean size, shape, visible absorption coefficient, and vertical distribution of aerosols in the Mars atmosphere. The calculation procedures are outlined, particularly for the particle size distribution function, which indicated a cross-sectional average particle radius of 2.5 microns. Dust-free conditions in the atmosphere near the equator and at lower altitudes permit full surface absorption of sunlight and subsequent adiabatic lapse rates. Difficulties were encountered in accurately modeling temperature profiles to fit Viking lander data, and resultant variations are attributed to effects of both suspended dust particles and large scale circulation.

The direct thermal effects of the refrigerant R-134A on atmospheric surface temperature

The direct thermal effect of refrigerant R-134A (1, 1, 1, 2-tetrafluoroethane) has been evaluated using a one-dimensional radiative-convective model of the atmosphere. The surface temperature increase from a uniform 1 ppbv distribution of R-134A was calculated to be less than 0.04 K, as compared to 0.14 K for 1 ppbv of R-12. Using recent extimates (Anderson L., 1981, Atmospheric Environment 15, 1579–1582) of 0.1 ppbv for the worst case ground level concentration of R-134A, our results give a temperature increase from direct thermal heating of 0.004 K, about an order of magnitude less than that from R-12.

An atmospheric radiative-convective model with interactive water vapor transport and cloud development

In the present generation of radiative-convective models, clouds are assigned specific levels or temperatures that do not change during the course of the calculations. In addition, a single water vapor distribution is used for the “mean atmosphere” instead of separate distributions for the clear sky and cloudy sky atmospheres. We present results from a one-dimensional radiative-convective model that includes interactive water vapor transport and predicts cloud altitudes and thicknesses. The fully interactive model and one with a single, fixed cloud with a single water vapor profile can both reproduce a mean global temperature profile, their surface temperatures agreeing within a few tenths of a degree of the observed surface temperature. However, for surface temperature sensitivity studies, major differences between the two models can exist. The differences result from the use of separate clear and cloudy sky water vapor profiles and from the coupling of cloud numbers, locations, and thicknesses to temperature. The interactive model's sensitivities to changes in the maximum altitude of convective extent, carbon dioxide, and surface relative humidity are presented. It is demonstrated that for global average conditions, the assumption of a constant distribution of relative humidity underestimates the water vapor amount and thermal contributions in radiative-convective models. DOI: 10.1111/j.2153-3490.1981.tb01759.x

Comparison of radiative-convective models with constant and pressure-dependent lapse rates

In the current generation of radiative-convective models a constant value for the critical atmospheric lapse rate, generally 6.5 K/km, is used. However, the moist adiabatic lapse rates are a better approximation for use in simple climate models. Thus, a comparison of temperature profiles with critical constant and moist adiabatic lapse rates has been made for a one-dimensional radiative-convective model. The commonly used lapse rate of 6.5 K/km yields surface temperatures some 1 to 3 K higher than with the use of moist adiabatic lapse rates for both clear sky conditions and a single effective cloud. When multiple clouds are included the constant lapse rate of 6.5 K/km yields the lower surface temperatures. More importantly, the surface temperature generated from the constant lapse rate formulation is more sensitive to changes in carbon dioxide, relative humidity, cloud cover, and surface albedo. For a doubling of CO 2 the moist adiabatic lapse rate formulation yields surface temperature changes 25 to 60% smaller than does a constant 6.5 K/km lapse rate depending on the cloud treatment. DOI: 10.1111/j.2153-3490.1981.tb01749.x

Climate Sensitivity of a One-Dimensional Radiative-Convective Model with Cloud Feedback

The potential complexity of the feedback between global mean cloud amount and global mean surface temperature when variations of the vertical cloud distribution are included is illustrated. This is done by studying the behavior of a one-dimensional radiative-convective model with two types of cloud variation: (1) variable cloud cover with constant optical thickness and (2) variable optical thickness with constant cloud cover. The variable parameter is calculated on the assumption that a correlation exists between cloud amount and precipitation or the vertical flux convergence of latent heat. Since the vertical latent heat flux is taken to be a fraction of the total heat flux, modeled by convective adjustment, the sensitivity of the results to two different critical lapse rates is examined. These are a constant 6.5 K/km lapse rate and a temperature-dependent, moist adiabatic lapse rate. The effects of the vertical structure of climate perturbations on the nature of the cloud feedback are also examined. The model results reveal that changes in the vertical cloud distribution and mean cloud optical thickness can be as important to climate variations as are changes in the total cloud cover.

Cloud Optics as a Possible Stabilizing Factor in Climate Change

Calculations made with a one-dimensional radiative-convective climate model show that the optical properties of clouds in solar wavelengths can be a stabilizing factor in climate change. Cloud reflectivity and absorption have been calculated as functions of cloud liquid water content using the parameterization of Liou and Wittman (1979). With the assumption that cloud liquid water content increases (decreases) as temperature and absolute humidity increase (decrease) during a climate perturbation, cloud reflectivity increases (decreases), damping the original perturbation by a few tens of percent. This probably should be regarded as an upper limit on the amount of negative feedback which changes in solar wavelength cloud optical properties (for fixed cloud area) can provide in a global climate model.

Clouds and Climate: Sensitivity of Simple Systems

Abstract A one-dimensional radiative convective model is used to gage the influence of clouds on simple climate systems. The radiative transfer model is developed to accommodate in a systematic and consistent manner the optical properties of a hierachy of cloud types. Cloud albedo and emissivity relationships for both ice and water clouds are introduced. The model structure is highly sensitive to cloud height for all cloud types and particularly sensitive to water path for optically thin clouds. High thin clouds at low and middle latitudes in all seasons and all clouds at high latitudes in winter tend to warm the surface relative to the clear sky; all other clouds tend to cool the surface. The summer high-latitude effects are similar to the low- and middle-latitude situation. The model sensitivity is compounded by surface albedo effects. For a given cloud a critical surface albedo may exist at which the cloud transits from cooling the surface relative to clear-sky conditions to warming the surface when th...

An atmospheric radiative-convective model with interactive water vapor transport and cloud development

In the present generation of radiative-convective models, clouds are assigned specific levels or temperatures that do not change during the course of the calculations. In addition, a single water vapor distribution is used for the “mean atmosphere” instead of separate distributions for the clear sky and cloudy sky atmospheres. We present results from a one-dimensional radiative-convective model that includes interactive water vapor transport and predicts cloud altitudes and thicknesses.The fully interactive model and one with a single, fixed cloud with a single water vapor profile can both reproduce a mean global temperature profile, their surface temperatures agreeing within a few tenths of a degree of the observed surface temperature. However, for surface temperature sensitivity studies, major differences between the two models can exist.The differences result from the use of separate clear and cloudy sky water vapor profiles and from the coupling of cloud numbers, locations, and thicknesses to temperature. The interactive model’s sensitivities to changes in the maximum altitude of convective extent, carbon dioxide, and surface relative humidity are presented. It is demonstrated that for global average conditions, the assumption of a constant distribution of relative humidity underestimates the water vapor amount and thermal contributions in radiative-convective models.

Comparison of radiative-convective models with constant and pressure-dependent lapse rates

In the current generation of radiative-convective models a constant value for the critical atmospheric lapse rate, generally 6.5 K/km, is used. However, the moist adiabatic lapse rates are a better approximation for use in simple climate models. Thus, a comparison of temperature profiles with critical constant and moist adiabatic lapse rates has been made for a one-dimensional radiative-convective model. The commonly used lapse rate of 6.5 K/km yields surface temperatures some 1 to 3 K higher than with the use of moist adiabatic lapse rates for both clear sky conditions and a single effective cloud. When multiple clouds are included the constant lapse rate of 6.5 K/km yields the lower surface temperatures. More importantly, the surface temperature generated from the constant lapse rate formulation is more sensitive to changes in carbon dioxide, relative humidity, cloud cover, and surface albedo. For a doubling of CO2 the moist adiabatic lapse rate formulation yields surface temperature changes 25 to 60% smaller than does a constant 6.5 K/km lapse rate depending on the cloud treatment.

Aerosol, Cloud Reflectivity and Climate

Abstract Changes in aerosol concentrations could imply changes in cloud condensation nuclei concentrations, which could in turn affect cloud optical properties. Calculations made with a one-dimensional radiative-convective model show that this can be a significant mechanism for climate change.

Effect of Ice-Albedo Feedback on Global Sensitivity in a One-Dimensional Radiative-Convective Climate Model

Abstract The feedback between ice albedo and temperature is included in a one-dimensional radiative-convective climate model. The effect of this feedback on global sensitivity to changes in solar constant is studied for the current climate conditions. This ice-albedo feedback amplifies global sensitivity by 26 and 39%, respectively, for assumptions of fixed cloud altitude and fixed cloud temperature. The global sensitivity is not affected significantly if the latitudinal variations of mean solar zenith angle and cloud cover are included in the global model. The differences in global sensitivity between one-dimensional radiative-convective models and energy balance models are examined. It is shown that the models are in close agreement when the same feedback mechanisms are included. The one-dimensional radiative-convective model with ice-albedo feedback included is used to compute the equilibrium ice line as a function of solar constant. It is found that the fixed cloud temperature parameterization breaks ...

Climatic Effects Due to Halogenated Compounds in the Earth’s Atmosphere

Using a one-dimensional radiative-convective model, we perform a sensitivity study of the effect of ozone depletion in the stratosphere on the surface temperature. There could be a cooling of the surface temperature by ~0.2 K due to chlorofluoromethane-induced ozone depletion at steady state (assuming 1973 release rates). This cooling reduces significantly the greenhouse effect due to the presence of chlorofluoromethanes. Carbon tetrafluoride has a strong ν_3 band at 7.8 μm, and the atmospheric greenhouse effect is shown to be 0.07 and 0.12 K (ppbv)^(−1) with and without taking into account overlap with CH_4 and N_2O bands. At concentration higher than 1 ppbv, absorption by the ν_3 band starts to saturate and the greenhouse effect becomes less efficient.

Greenhouse Effects due to Man-Made Perturbations of Trace Gases

Nitrous oxide, methane, ammonia, and a number of other trace constituents in the earth's atmosphere have infrared absorption bands in the spectral region 7 to 14 microm and contribute to the atmospheric greenhouse effect. The concentrations of these trace gases may undergo substantial changes because of man's activities. Extensive use of chemical fertilizers and combustion of fossil fuels may perturb the nitrogen cycle, leading to increases in atmospheric N(2)O, and the same perturbing processes may increase the amounts of atmospheric CH(4) and NH(3). We use a one-dimensional radiative-convective model for the atmospheric thermal structure to compute the change in the surface temperature of the earth for large assumed increases in the trace gas concentrations; doubling the N(2)O, CH(4), and NH(3) concentrations is found to cause additive increases in the surface temperature of 0.7 degrees , 0.3 degrees , and 0.1 degrees K, respectively. These systematic effects on the earth's radiation budget would have substantial climatic significance. It is therefore important that the abundances of these trace gases be accurately monitored to determine the actual trends of their concentrations.