Showing papers on "Solar constant published in 1985"

Transient climate response to external forcing on 100–104 year time scales: 2. Sensitivity experiments with a seasonal, hemispherically averaged, coupled atmosphere, land, and ocean energy balance model

Abstract: We present a hemispherically averaged, seasonal model with land-sea and surface-air resolution that we use to compare the transient temperature response of different model components to changes in the radiative forcing. Horizontal heat transport coefficients were obtained by tuning the model to reproduce the present seasonal climate as closely as possible. Cross-sensitivity experiments with a step function solar constant increase and a variety of ocean parameter feedback processes essentially duplicate the results obtained in part 1 (Harvey and Schneider, 1985) with a globally averaged model. We intercompare the global and hemispheric model surface and deep-ocean transient response and show how both the global mean surface and mixed-layer only transient response of the hemispheric model can be reproduced by using the globally averaged model. For a time-dependent CO2 increase scenario we find that the mixed-layer warming lags moderately behind the atmosphere wanning but that the atmosphere over land and atmosphere over sea warmings are rather tightly coupled. Implementation of a number of ocean parameter feedbacks to a time-dependent CO2 increase has a similar qualitative effect on the transient temperature response as when implemented for a step function solar constant increase but causes less variation in the transient response than uncertainties about the equilibrium climate sensitivity. During the first year following a small negative perturbation to the solar constant, in order to mimic a volcanic dust veil, we find that the air temperature response over land is about twice that of the ocean mixed-layer temperature. This suggests that one should distinguish between temperature responses over land and over ocean in any studies attempting to compare model-generated volcanic signals with empirical surface temperature data. For complex short- and long-term mixed forcing changes, such as volcanic and CO2, the lag between atmosphere and mixed-layer temperature changes does not become large until the long-term forcing change becomes dominant, although the land-sea lags associated with short-term perturbations may still be significant for regional climatic anomalies associated with these perturbations.

Solar absolute spectral irradiance 118–300 nm: July 25, 1983

Abstract: The full-disk solar absolute spectral irradiance in the spectral range 118-300 nm was obtained from a rocket observation above White Sands Missile Range, NM, on July 25, 1983, halfway in time between solar maximum and solar minimum. Comparison with measurements made in May 1982 shows no changes within the absolute errors of the experiment. Comparison with measurements made during solar maximum in 1979 and 1980 indicates a large decrease in the absolute solar irradiance at wavelengths below 190 nm. The absolute calibration of the instruments for this flight was accomplished at the National Bureau of Standards Synchrotron Radiation Facility.

The importance of improved facular observations in understanding solar constant variations

Abstract: A new study of solar irradiance modeling has been undertaken to improve the previous modeling efforts and perhaps to resolve the energy-balance question. In the present study, the daily sunspot and facular areas (using plages as a proxy measure of faculae) have been utilized, as well as a plage intensity index to examine brightness variations. It is noted that the reported plage areas changed by a factor of 2 near the end of 1979. Although this can be partially modeled because a commensurate change in plage brightness occurs, it leads to the conclusion that facular areas and brightness uncertainties prevent a definitive answer to the energy-balance question with this technique.

Activity of sunspots and solar constant variations during 1980

Abstract: A strong inverse correlation is shown between the irradiance dips observed by the SMM/ACRIM radiometer and the projected areas of the ‘active’ sunspots. This strong correlation and the results of a preliminary time series analysis indicate that the value of the solar constant decreased when quickly developing sunspot groups with complex structure occurred on the solar disk. On the other hand, when the old groups with simple structure were dominant the value of the solar constant increased slightly or these groups could reduce the effects of the ‘active’ spots. On the basis of our investigations it seems that the formation of the sunspots and the new activity of the older ones as well as the decreases of the solar constant may be the common symptoms of such a physical process which takes place in deeper regions of the Sun through the interaction of magnetic fields with the convection.

The effect of a solar perturbation on a global climate model.

Abstract: A quasi-three-dimensional global climate model is used to study the effect of a transient change in solar radiation on the model's climate. The solar constant is decreased abruptly by 5 percent in the 10th year of a 50-year run. It is then returned to its original value at increments of 1 percent per year. Although significant changes occur during the perturbation including a drop in the average global surface temperature of about 2.6 K, the long-term effects on the model's climate are small.

Data on total and spectral solar irradiance: reply to comments.

Abstract: The letter is a response to Frohlich's (1983) comments on an earlier paper (Mecherikunnel et al., 1983) containing a brief survey of the available data on the solar constant and its spectral distribution. The sources of the initial data used in the above study are mentioned, and comments are made on the accuracy of the measurements. Reasons are given for using NASA/ASTM data in the computations.

Parameterizations of cloud feedback in a radiative-convective model

Abstract: The effect of cloud feedback on the response of a radiative-convective model to a change in cloud model parameters, atmospheric CO2 concentration, and solar constant has been studied using two different parameterization schemes. The method for simulating the vertical distribution of both cloud cover and cloud optical thickness, which depends on the relative humidity and on the saturation mixing ratio of water vapor, respectively, is the same in both approaches, but the schemes differ with respect to modeling the water vapor profile. In scheme I atmospheric water vapor is coupled to surface parameters, while in scheme II an explicit balance equation for water vapor in the individual atmospheric layers is used. For both models the combined effect of feedbacks due to variations in lapse rate, cloud cover, and cloud optical thickness results in different relationships between changes in surface temperature, planetary temperature, and cloud cover. Specifically, for a CO2 doubling and a 2% increase in solar constant, in both models the surface warming is reduced by cloud feedback, in contrast to no feedback, with the greater reduction in scheme I as compared to that of scheme II.

An upper limit to global surface air temperature

Abstract: Several empirical studies of Earth's surface air temperature and radiation budget have indicated that there is an upper limit above which the mean surface air temperature of the globe cannot rise, as long as the solar constant and the mass of the Earth's atmosphere remain unchanged. It is shown that current state-of-the-art climate models suggest the same thing and that they yield a comparable value for the maximum warming attainable: 4–5 K.

A relationship between the decrease in solar constant and the north-south flow in the Galician current

Abstract: The following hypothesis is exposed: Variations of the oceanic currents depend mainly on these two factors: (a) the variation of the solar cnergy fluir; and (b) Lhc encrgy dlssipated from Earth's variable rotation. In oceanic currents Iiaving an E-W dircction the main factor will be polar motion, but in ctirrents N-S this factor will be variations of the solar energy Hilx. Peviously thc authors liad studicd the effect of polar motion in marine ecosystems of the North Atlantic Ocean, where currents have a W-E rnain direction. Now an essay is carried out to test if in N-S currents the variation of the solar energy flux acts as a perceptible factor. Percent of decrease in solar constant and coefficient of variation for the first Empirical ürthogonnl Function in the California Current, as an example oi N-S current, have becn used. Relationship between these two factors appears to be signiíicant, and the time lag between changes of the solar energy flux and response of the current flow seems to be about 3-9 rnonths. A seasonal variation of the velocity of the Kuroshio seems to confirrn this solar energy role in oceanic currents.