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Abstract
The radiation budget of the northern-hemisphere stratosphere, as a function of the mean thermal structure and composition of the stratosphere, is determined for the months of January, April, July, and October. Emission of infrared radiation by carbon dioxide, water vapor, and ozone is calculated by means of a simple numerical method derived from the differential equations of radiative transfer. Absorption of solar radiation by ozone is taken from published results; absorption of solar energy by water vapor is computed with the aid of an empirical formula.
It is found that, in general, radiative equilibrium is not obtained at any latitude. Low latitudes constitute a heat source and high latitudes a heat sink in the stratospheric energy budget. It is shown that carbon dioxide is more important than water vapor in cooling the stratosphere and that infrared transfer in the 9.6µ ozone band normally results in a convergence of energy in the stratosphere.
Some features of the stratospheric temperature distribution and circulation pattern are inferred from the computed radiation budget and its seasonal variations.
Abstract
The radiation budget of the northern-hemisphere stratosphere, as a function of the mean thermal structure and composition of the stratosphere, is determined for the months of January, April, July, and October. Emission of infrared radiation by carbon dioxide, water vapor, and ozone is calculated by means of a simple numerical method derived from the differential equations of radiative transfer. Absorption of solar radiation by ozone is taken from published results; absorption of solar energy by water vapor is computed with the aid of an empirical formula.
It is found that, in general, radiative equilibrium is not obtained at any latitude. Low latitudes constitute a heat source and high latitudes a heat sink in the stratospheric energy budget. It is shown that carbon dioxide is more important than water vapor in cooling the stratosphere and that infrared transfer in the 9.6µ ozone band normally results in a convergence of energy in the stratosphere.
Some features of the stratospheric temperature distribution and circulation pattern are inferred from the computed radiation budget and its seasonal variations.
Abstract
Stepwise multiple regression analyses are used to explore the statistical (linear regression) relationships between satellite-observed earth–atmosphere emission spectra and meteorological parameters. The stepwise regression technique permits screening of a large number of potentially useful spectral observations (predictors) to isolate those few that contribute most to the explanation of the variance of a particular meteorological parameter. Such a technique is particularly useful when applied to complete spectra of the type obtained by the IRIS (infrared interferometer spectrometer) instrument on the recent Nimbus meteorological satellites. Emphasis is placed upon inferences of key meteorological parameters not usually obtained from routine inversion of satellite spectral observations. The technique is applied to a sample of Nimbus 3 IRIS spectra. The results indicate that information on atmospheric temperatures, geopotential heights of pressure surfaces, tropopause pressure, and tropopause temperature can be obtained directly from the satellite observations with the use of simple linear relationships having only a few terms each. Based upon the results of this exploratory study, suggestions are made for further development and exploitation of the stepwise regression analysis technique and its application to the problem of inferring meteorological parameters from earth–atmosphere emission spectra of the IRIS type.
Abstract
Stepwise multiple regression analyses are used to explore the statistical (linear regression) relationships between satellite-observed earth–atmosphere emission spectra and meteorological parameters. The stepwise regression technique permits screening of a large number of potentially useful spectral observations (predictors) to isolate those few that contribute most to the explanation of the variance of a particular meteorological parameter. Such a technique is particularly useful when applied to complete spectra of the type obtained by the IRIS (infrared interferometer spectrometer) instrument on the recent Nimbus meteorological satellites. Emphasis is placed upon inferences of key meteorological parameters not usually obtained from routine inversion of satellite spectral observations. The technique is applied to a sample of Nimbus 3 IRIS spectra. The results indicate that information on atmospheric temperatures, geopotential heights of pressure surfaces, tropopause pressure, and tropopause temperature can be obtained directly from the satellite observations with the use of simple linear relationships having only a few terms each. Based upon the results of this exploratory study, suggestions are made for further development and exploitation of the stepwise regression analysis technique and its application to the problem of inferring meteorological parameters from earth–atmosphere emission spectra of the IRIS type.
Abstract
A nonstatistical method for obtaining ballistic densities directly from satellite radiance observations is derived. The method takes advantage of the fact that both the ballistic density and the satellite radiances depend upon weighted vertical integrals of the atmospheric temperature. Tests of the method on realistically simulated satellite radiances indicate root-mean-square retrieval errors of 1/4;–1/3; of the standard deviation of ballistic density for individual months. The method thus appears to be suitable for application to areas of the globe with a paucity of conventional radiosonde observations.
Abstract
A nonstatistical method for obtaining ballistic densities directly from satellite radiance observations is derived. The method takes advantage of the fact that both the ballistic density and the satellite radiances depend upon weighted vertical integrals of the atmospheric temperature. Tests of the method on realistically simulated satellite radiances indicate root-mean-square retrieval errors of 1/4;–1/3; of the standard deviation of ballistic density for individual months. The method thus appears to be suitable for application to areas of the globe with a paucity of conventional radiosonde observations.
Abstract
Due to the opposing albedo and greenhouse effects of clouds, the possibility exists that the net radiation at the top of the earth-atmosphere system is, in the mean, insensitive to changes in cloud amount. If so, this would have important implications for climate studies. This question is examined with the use of data on the components of the radiation budget at the top of the atmosphere obtained from the processing of 45 months of scanning radiometer observations of the NOAA satellites. Year-to-year changes in monthly mean values of outgoing longwave radiation and albedo are analysed at a sample of geographic and climatic areas of the earth. By using the albedo changes as a measure of changes in cloud amount, it is possible to determined the sensitivity of the outgoing longwave radiation and the net radiation to changes in cloud amount. For each geographic/climatic area, the results indicate that the net radiation at the top of the atmosphere is sensitive to cloud amount changes and the sensitivity is such that the albedo effect of the clouds predominates over their greenhouse effect. Thus, for the earth as a whole the net radiation at the top of the atmosphere is sensitive to changes in cloud amount. Estimates of the numerical values of the global mean sensitivity of net radiation and outgoing longwave radiation to changes in cloud amount are presented and compared with previous findings.
Abstract
Due to the opposing albedo and greenhouse effects of clouds, the possibility exists that the net radiation at the top of the earth-atmosphere system is, in the mean, insensitive to changes in cloud amount. If so, this would have important implications for climate studies. This question is examined with the use of data on the components of the radiation budget at the top of the atmosphere obtained from the processing of 45 months of scanning radiometer observations of the NOAA satellites. Year-to-year changes in monthly mean values of outgoing longwave radiation and albedo are analysed at a sample of geographic and climatic areas of the earth. By using the albedo changes as a measure of changes in cloud amount, it is possible to determined the sensitivity of the outgoing longwave radiation and the net radiation to changes in cloud amount. For each geographic/climatic area, the results indicate that the net radiation at the top of the atmosphere is sensitive to cloud amount changes and the sensitivity is such that the albedo effect of the clouds predominates over their greenhouse effect. Thus, for the earth as a whole the net radiation at the top of the atmosphere is sensitive to changes in cloud amount. Estimates of the numerical values of the global mean sensitivity of net radiation and outgoing longwave radiation to changes in cloud amount are presented and compared with previous findings.
Abstract
The seasonal and latitudinal variations of the average surface temperature and vertical profile of atmospheric temperature on Mars are computed using a thermal equilibrium model. It is assumed that carbon dioxide is the sole radiating gas in a model atmosphere that is composed of 60% carbon dioxide and has a surface pressure of 10 mb. The results are presented in the form of pole-to-pole temperature cross sections from the surface to about 40 km for each Martian season. The computed temperature cross sections indicate: 1) extremely small latitudinal temperature gradients in the summer hemisphere, with the maximum temperature occurring at the pole; 2) a decrease of tropopause altitude with latitude from a maximum at the equator during the equinoctial seasons and at the summer pole during the solstices; and 3) relatively isothermal vertical structure at high latitudes during the equinoxes and winter. Comparisons, where possible, of the present results with other theoretical studies and with the microwave observational indications of Martian temperatures yield generally good agreement.
Abstract
The seasonal and latitudinal variations of the average surface temperature and vertical profile of atmospheric temperature on Mars are computed using a thermal equilibrium model. It is assumed that carbon dioxide is the sole radiating gas in a model atmosphere that is composed of 60% carbon dioxide and has a surface pressure of 10 mb. The results are presented in the form of pole-to-pole temperature cross sections from the surface to about 40 km for each Martian season. The computed temperature cross sections indicate: 1) extremely small latitudinal temperature gradients in the summer hemisphere, with the maximum temperature occurring at the pole; 2) a decrease of tropopause altitude with latitude from a maximum at the equator during the equinoctial seasons and at the summer pole during the solstices; and 3) relatively isothermal vertical structure at high latitudes during the equinoxes and winter. Comparisons, where possible, of the present results with other theoretical studies and with the microwave observational indications of Martian temperatures yield generally good agreement.
Abstract
A simple, zonally averaged numerical model is developed for simulating certain features of the annual mean climate of the Northern Hemisphere. The model is based on the two-level quasi-geostrophic potential vorticity system of equations and a surface beat balance equation. Ale main output consists of the latitudinal variations of temperature at the surface and 500 mb and of zonal wind at 250 and 750 mb. Meridional transport of quasi-geostrophic potential vorticity is simulated by an eddy ~ process using exchange coefficients based on observational data. Solar radiative processes included are absorption by water vapor, ozone and cloud particles, scattering by air molecules and clouds, and reflection by the surface. Longwave radiative processes include absorption and emission by water vapor, carbon dioxide and clouds. Other beat transfer processes–convection, evaporation, condensation and ocean currents–are pammeterized.
Using present boundary conditions, the model is used to compute the present climate. Comparison of the computed climate with the observed climate shows good agreement. A special attempt is made to compare some of the radiation quantities computed by the model with satellite observations and radiation budget calculations.
The sensitivity of the computed climate to changes in some of the boundary conditions is investigated. These sensitivity experiments are performed with and without an ice feedback mechanism. The ice feedback mechanism is based on empirical relations between the fractions of a latitude belt covered by snow and ice in winter and slimmer and the mean annual surface temperature. When the atmospheric carbon dioxide content is doubled, the hemispheric mean surface temperature increases by 0.5°C in the absence of ice feedback, the largest increases taking place at high latitudes. Ice albedo feedback amplifies the hemispheric average temperature change by about 50%; amplifications as large as several hundred percent are obtained in polar regions. A change in mean surface temperature of ±1°C for a ±1% change in solar constant is obtained in the absence of ice feedback, but this is amplified to −1.5°C (decreased solar constant) and 1.4°C (increased solar constant) when ice feedback is included. As In the 2×CO2 case, polar amplification factors due to ice albedo feedback are several hundred percent. When hemispheric cloud amount is increased, the surface temperature decreases but in the absence of ice feedback the magnitude of the change approaches zero near the poles. A hemispheric increase in the altitude of the cloud layer causes an increase in surface temperatures. These results are compared with those obtained with other climate models.
Abstract
A simple, zonally averaged numerical model is developed for simulating certain features of the annual mean climate of the Northern Hemisphere. The model is based on the two-level quasi-geostrophic potential vorticity system of equations and a surface beat balance equation. Ale main output consists of the latitudinal variations of temperature at the surface and 500 mb and of zonal wind at 250 and 750 mb. Meridional transport of quasi-geostrophic potential vorticity is simulated by an eddy ~ process using exchange coefficients based on observational data. Solar radiative processes included are absorption by water vapor, ozone and cloud particles, scattering by air molecules and clouds, and reflection by the surface. Longwave radiative processes include absorption and emission by water vapor, carbon dioxide and clouds. Other beat transfer processes–convection, evaporation, condensation and ocean currents–are pammeterized.
Using present boundary conditions, the model is used to compute the present climate. Comparison of the computed climate with the observed climate shows good agreement. A special attempt is made to compare some of the radiation quantities computed by the model with satellite observations and radiation budget calculations.
The sensitivity of the computed climate to changes in some of the boundary conditions is investigated. These sensitivity experiments are performed with and without an ice feedback mechanism. The ice feedback mechanism is based on empirical relations between the fractions of a latitude belt covered by snow and ice in winter and slimmer and the mean annual surface temperature. When the atmospheric carbon dioxide content is doubled, the hemispheric mean surface temperature increases by 0.5°C in the absence of ice feedback, the largest increases taking place at high latitudes. Ice albedo feedback amplifies the hemispheric average temperature change by about 50%; amplifications as large as several hundred percent are obtained in polar regions. A change in mean surface temperature of ±1°C for a ±1% change in solar constant is obtained in the absence of ice feedback, but this is amplified to −1.5°C (decreased solar constant) and 1.4°C (increased solar constant) when ice feedback is included. As In the 2×CO2 case, polar amplification factors due to ice albedo feedback are several hundred percent. When hemispheric cloud amount is increased, the surface temperature decreases but in the absence of ice feedback the magnitude of the change approaches zero near the poles. A hemispheric increase in the altitude of the cloud layer causes an increase in surface temperatures. These results are compared with those obtained with other climate models.
Abstract
A method is suggested for introducing long-term interaction between the geobotanic state and climate (a biogeophysical feedback mechanism) into climate models. It is based upon making the geobotanic state, characterized by the snow-free surface albedo and the water availability parameter, dependent upon the ratio of annual radiation balance to annual precipitation (the so-called radiative index of dryness).
This approach is illustrated using a zonally averaged annual steady-state climate model which is based on the hemispheric climate model of Ohring and Adler. Zonal data statistics are employed to obtain simple relationships consistent with the zonality of the system. The heating parameterization of the original model is modified so that precipitation and cloud amount are computed using vertical velocity at 500 mb, which is calculated from the thermodynamic equation.
Experiments with the model indicate that the simulated climate and geobotanic zones are in good agreement with observations. Sensitivity studies suggest that biogeophysical feedback has a negligible effect on the model's response to solar constant variations but may be important in the evaluation of the long-term impact of surface albedo changes.
Abstract
A method is suggested for introducing long-term interaction between the geobotanic state and climate (a biogeophysical feedback mechanism) into climate models. It is based upon making the geobotanic state, characterized by the snow-free surface albedo and the water availability parameter, dependent upon the ratio of annual radiation balance to annual precipitation (the so-called radiative index of dryness).
This approach is illustrated using a zonally averaged annual steady-state climate model which is based on the hemispheric climate model of Ohring and Adler. Zonal data statistics are employed to obtain simple relationships consistent with the zonality of the system. The heating parameterization of the original model is modified so that precipitation and cloud amount are computed using vertical velocity at 500 mb, which is calculated from the thermodynamic equation.
Experiments with the model indicate that the simulated climate and geobotanic zones are in good agreement with observations. Sensitivity studies suggest that biogeophysical feedback has a negligible effect on the model's response to solar constant variations but may be important in the evaluation of the long-term impact of surface albedo changes.
Abstract
Nimbus-7 satellite observations are used to determine the relationship between the total longwave radiation flux and the radiance in the 10-12 μm infrared window. The total longwave fluxes are obtained from the earth radiation budget (ERB) narrow-field-of-view (NFOV) observations of total radiance; the IR window radiances are those measured by the Temperature Humidity Infrared Radiometer (THIR). Regression equations are obtained relating the total flux equivalent brightness temperatures to the radiance equivalent brightness temperature of the IR window. These empirical equations are compared to similar regression equations based on radiative transfer calculations for a large sample of atmospheric soundings. The latter theoretical equations are used by NOAA in the processing of IR window observations from operational polar orbiting satellites to obtain total longwave flux estimates. The observational results indicate that there is a very high correlation between the flux equivalent brightness temperature and the IR window radiance equivalent brightness temperature, and that the former can indeed be determined from measurements of the latter, thus validating the general NOAA approach. Tests on independent data suggest that rms flux errors of ∼11 w m−2 are to be expected for single applications of the empirical equations. The theoretical equations used by NOAA have an average positive bias of ∼13 wm−2 or a relative bias of ∼6% with respect to the ERB NFOV observations; the relative bias disappears at high flux values and increases with decreasing flux. A preliminary attempt to determine the cause of the discrepancy between the empirical and theoretical results indicates that a major factor may be the unrepresentativeness of the atmospheric soundings used in developing the theoretical regression coefficients.
Abstract
Nimbus-7 satellite observations are used to determine the relationship between the total longwave radiation flux and the radiance in the 10-12 μm infrared window. The total longwave fluxes are obtained from the earth radiation budget (ERB) narrow-field-of-view (NFOV) observations of total radiance; the IR window radiances are those measured by the Temperature Humidity Infrared Radiometer (THIR). Regression equations are obtained relating the total flux equivalent brightness temperatures to the radiance equivalent brightness temperature of the IR window. These empirical equations are compared to similar regression equations based on radiative transfer calculations for a large sample of atmospheric soundings. The latter theoretical equations are used by NOAA in the processing of IR window observations from operational polar orbiting satellites to obtain total longwave flux estimates. The observational results indicate that there is a very high correlation between the flux equivalent brightness temperature and the IR window radiance equivalent brightness temperature, and that the former can indeed be determined from measurements of the latter, thus validating the general NOAA approach. Tests on independent data suggest that rms flux errors of ∼11 w m−2 are to be expected for single applications of the empirical equations. The theoretical equations used by NOAA have an average positive bias of ∼13 wm−2 or a relative bias of ∼6% with respect to the ERB NFOV observations; the relative bias disappears at high flux values and increases with decreasing flux. A preliminary attempt to determine the cause of the discrepancy between the empirical and theoretical results indicates that a major factor may be the unrepresentativeness of the atmospheric soundings used in developing the theoretical regression coefficients.
Abstract
Estimates of the average surface temperature on Mars are derived from radiative equilibrium considerations. A minimum possible surface temperature is estimated by computing the radiative equilibrium temperature that the Martian surface would have if the planet had no atmosphere. An estimate of the maximum possible value of the average surface temperature is obtained by computing the surface temperature that would result from a maximum greenhouse model. The computations indicate that the average surface temperature is in the range 219K to 233K. Comparisons of the theoretical computations with indications of surface temperature obtained from thermal emission observations are found to be in reasonable agreement.
Abstract
Estimates of the average surface temperature on Mars are derived from radiative equilibrium considerations. A minimum possible surface temperature is estimated by computing the radiative equilibrium temperature that the Martian surface would have if the planet had no atmosphere. An estimate of the maximum possible value of the average surface temperature is obtained by computing the surface temperature that would result from a maximum greenhouse model. The computations indicate that the average surface temperature is in the range 219K to 233K. Comparisons of the theoretical computations with indications of surface temperature obtained from thermal emission observations are found to be in reasonable agreement.
Abstract
Relationships between atmospheric ozone and meteorological parameters in the lower stratosphere over Europe are studied. Correlation coefficients between total ozone amount and temperature, geopotential height, and north-south wind component at 100 mb are presented. The distribution of ozone amounts in relation to stratospheric troughs and ridges is shown.
High ozone amounts are found to be associated with high temperatures, low geopotential heights, southerly winds, and cyclonic-contour curvatures in the lower stratosphere. The results are discussed qualitatively in terms of stratospheric motions and the distribution of ozone.
Abstract
Relationships between atmospheric ozone and meteorological parameters in the lower stratosphere over Europe are studied. Correlation coefficients between total ozone amount and temperature, geopotential height, and north-south wind component at 100 mb are presented. The distribution of ozone amounts in relation to stratospheric troughs and ridges is shown.
High ozone amounts are found to be associated with high temperatures, low geopotential heights, southerly winds, and cyclonic-contour curvatures in the lower stratosphere. The results are discussed qualitatively in terms of stratospheric motions and the distribution of ozone.
