Syukuro Manabe

Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity

Abstract Radiative convective equilibrium of the atmosphere with a given distribution of relative humidity is computed as the asymptotic state of an initial value problem. The results show that it takes almost twice as long to reach the state of radiative convective equilibrium for the atmosphere with a given distribution of relative humidity than for the atmosphere with a given distribution of absolute humidity. Also, the surface equilibrium temperature of the former is almost twice as sensitive to change of various factors such as solar constant, CO2 content, O3 content, and cloudiness, than that of the latter, due to the adjustment of water vapor content to the temperature variation of the atmosphere. According to our estimate, a doubling of the CO2 content in the atmosphere has the effect of raising the temperature of the atmosphere (whose relative humidity is fixed) by about 2C. Our model does not have the extreme sensitivity of atmospheric temperature to changes of CO2 content which was adduced by M...

CLIMATE AND THE OCEAN CIRCULATION1

Abstract The effect of the hydrology of the earths surface is incorporated into a numerical model of the general circulation of the atmosphere developed at the Geophysical Fluid Dynamics Laboratory of the Environmental Science Services Administration (ESSA). The primitive equation of motion is used for this study. The nine levels of the model are distributed so as to resolve the surface boundary layer and stratosphere. The depletion of solar radiation and the transfer of the terrestrial radiation are computed taking into consideration cloud and atmospheric absorbers such as water vapor, carbon dioxide, and ozone. The scheme treating the hydrology of our model involves the prediction of water vapor in the atmosphere and the prediction of soil moisture and snow cover. In order to represent the mositure-holding capacity of soil, the continent is assumed to be covered by boxes, which can store limited amounts of water. The ocean surface is idealized to be a completely wet surface without any heat capacity. T...

Transient Responses of a Coupled Ocean–Atmosphere Model to Gradual Changes of Atmospheric CO2. Part I. Annual Mean Response

An improved method for surface treatment of metallic materials is described herein. The improvement exists in that a surface treatment agent and a metallic material to be treated are placed in a treating device, heating of the metallic material to be treated up to a specific upper limit temperature higher than a transformation point of the metallic material and cooling of the metallic material down to a specific lower limit temperature lower than the transformation point are alternately and repeatedly carried out, an appropriate stress is applied to the material when it takes the lower limit temperature, and after an appropriate number of temperature cycles the applied stress is released when the material takes the lower limit temperature.

Simulated response of the ocean carbon cycle to anthropogenic climate warming

A 1995 report of the Intergovernmental Panel on Climate Change provides a set of illustrative anthropogenic CO2 emission models leading to stabilization of atmospheric CO2 concentrations ranging from 350 to 1,000 p.p.m. (refs 1–4). Ocean carbon-cycle models used in calculating these scenarios assume that oceanic circulation and biology remain unchanged through time. Here we examine the importance of this assumption by using a coupled atmosphere–ocean model of global warming for the period 1765 to 2065. We find a large potential modification to the ocean carbon sink in a vast region of the Southern Ocean where increased rainfall leads to surface freshening and increased stratification. The increased stratification reduces the downward flux of carbon and the loss of heat to the atmosphere, both of which decrease the oceanic uptake of anthropogenic CO2 relative to a constant-climate control scenario. Changes in the formation, transport and cycling of biological material may counteract the reduced uptake, but the response of the biological community to the climate change is difficult to predict on present understanding. Our simulation suggests that such physical and biological changes might already be occurring, and that they could substantially affect the ocean carbon sink over the next few decades.

Two Stable Equilibria of a Coupled Ocean-Atmosphere Model

Abstract Two stable equilibria have been obtained from a global model of the coupled ocean-atmosphere system developed at the Geophysical Fluid Dynamics Laboratory of NOAA. The model used for this study consists of general circulation models of the atmosphere and the world oceans and a simple model of land surface. Starting from two different initial conditions, “asynchronous” time integrations of the coupled model, under identical boundary conditions, lead to two stable equilibria. In one equilibrium, the North Atlantic Oman has a vigorous thermohaline circulation and relatively saline and warm surface water. In the other equilibrium, there is no thermohaline circulation, and an intense halocline exists in the surface layer at high latitudes. In both integration the, air-sea exchange of water is adjusted to remove a systematic bias of the model that surpresses the thermohaline circulation in the North Atlantic. Nevertheless these results raise the intriguing possibility that the coupled system may have a...

Interdecadal Variations of the Thermohaline Circulation in a Coupled Ocean-Atmosphere Model

Abstract A fully coupled ocean-atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the North Atlantic Ocean with a time scale of approximately 50 years. The irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation (approximately 52°N to 72°N) combined with much smaller density anomalies of opposite sign in the broad, rising region. The spatial pattern of see surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the North Atlantic. The anomalies of sea surface temperature induce model surface air temperature anomalies over the northern North Atlantic, Arctic, and northwestern Europe.

The Effects of Doubling the CO2 Concentration on the climate of a General Circulation Model

Abstract An attempt is made to estimate the temperature changes resulting from doubling the present CO2 concentration by the use of a simplified three-dimensional general circulation model. This model contains the following simplications: a limited computational domain, an idealized topography, no beat transport by ocean currents, and fixed cloudiness. Despite these limitations, the results from this computation yield some indication of how the increase of CO2 concentration may affect the distribution of temperature in the atmosphere. It is shown that the CO2 increase raises the temperature of the model troposphere, whereas it lowers that of the model stratosphere. The tropospheric warming is somewhat larger than that expected from a radiative-convective equilibrium model. In particular, the increase of surface temperature in higher latitudes is magnified due to the recession of the snow boundary and the thermal stability of the lower troposphere which limits convective beating to the lowest layer. It is ...

Thermal Equilibrium of the Atmosphere with a Convective Adjustment

Abstract The states of thermal equilibrium (incorporating an adjustment of super-adiabatic stratification) as well as that of pure radiative equilibrium of the atmosphere are computed as the asymptotic steady state approached in an initial value problem. Recent measurements of absorptivities obtained for a wide range of pressure are used, and the scheme of computation is sufficiently general to include the effect of several layers of clouds. The atmosphere in thermal equilibrium has an isothermal lower stratosphere and an inversion in the upper stratosphere which are features observed in middle latitudes. The role of various gaseous absorbers (i.e., water vapor, carbon dioxide, and ozone), as well as the role of the clouds, is investigated by computing thermal equilibrium with and without one or two of these elements. The existence of ozone has very little effect on the equilibrium temperature of the earths surface but a very important effect on the temperature throughout the stratosphere; the absorption...

Multiple-Century Response of a Coupled Ocean-Atmosphere Model to an Increase of Atmospheric Carbon Dioxide

Abstract To speculate on the future change of climate over several centuries, three 500-year integrations of a coupled ocean-atmosphere model were performed. In addition to the standard integration in which the atmospheric concentration of carbon dioxide remains unchanged, two integrations are conducted. In one integration, the C02 concentration increases by 1% yr−1 (compounded) until it reaches four times the initial value at the 140th year and remains unchanged thereafter. In another integration, the C02 concentration also increases at the rate of 1% yr−1 until it reaches twice the initial value at the 70th year and remains unchanged thereafter. One of the most notable features of the C02-quadrupling integration is the gradual disappearance of thermohaline circulations in most of the model oceans during the first 250-year period, leaving behind wind-driven cells. For example, thermohaline circulation nearly vanishes in the North Atlantic during the fist 200 years of the integration. In the Weddell and R...

The Role of Mountains in the South Asian Monsoon Circulation

Abstract An 11–level numerical model of the atmospheric circulation which has a prescribed seasonal variation of insulation and sea surface temperatures is integrated with respect to time for approximately three model years. The model is global in domain and incorporates a smoothed mountain topography. In order to investigate the role that mountains play in the south Asian monsoon circulation, a second numerical experiment, exactly the same as the first except that all mountains are removed, is integrated with respect to time from 25 March through July. Analysis of the model with mountains reveals that the large–scale circulation associated with the south Asian monsoon is well simulated. However, the onset of the monsoon is approximately 10–15 days later than normal, and the atmosphere over the western Pacific seems to he dynamically too active, while the atmosphere over the northern reaches of the Bay of Bengal and northern India is relatively inactive. Comparison of the simulation with mountains with th...