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- Author or Editor: George Ohring x
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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
Based on simulations, a simple linear relationship is derived between planetary albedo and the surface albedo for the case of clear skies. This relationship enables one to estimate the planetary albedo, given only the surface albedo, and vice versa. The standard error of estimate is 0.028. The estimation of planetary albedo from surface albedo is checked by comparing zonally averaged clear-sky planetary albedos estimated from zonally averaged surface albedos, to satellite determinations of zonally averaged minimum albedos for monthly mean conditions. The minimum albedos are assumed to be representative of the clear-sky planetary albedos. The results show root-mean square differences of 0.05 between the estimated clear-sky planetary albedos and them albedos.
More accurate relationships can be obtained if one uses an additional parameter-the solar zenith angle. In this case, the standard errors of estimate are reduced to 0.017 for a zenith angle of 0°,0/018 for a zenith angle of 60° and 0.021 for a zenith of 85°.
Abstract
Based on simulations, a simple linear relationship is derived between planetary albedo and the surface albedo for the case of clear skies. This relationship enables one to estimate the planetary albedo, given only the surface albedo, and vice versa. The standard error of estimate is 0.028. The estimation of planetary albedo from surface albedo is checked by comparing zonally averaged clear-sky planetary albedos estimated from zonally averaged surface albedos, to satellite determinations of zonally averaged minimum albedos for monthly mean conditions. The minimum albedos are assumed to be representative of the clear-sky planetary albedos. The results show root-mean square differences of 0.05 between the estimated clear-sky planetary albedos and them albedos.
More accurate relationships can be obtained if one uses an additional parameter-the solar zenith angle. In this case, the standard errors of estimate are reduced to 0.017 for a zenith angle of 0°,0/018 for a zenith angle of 60° and 0.021 for a zenith of 85°.
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.
Abstract
Radiational heating of the mesosphere results principally from absorption of ultraviolet radiation by ozone. For conditions of photochemical equilibrium, the amount of ozone present near the mesopeak depends critically on the temperature. Relatively high temperature results in less ozone and less heating. Calculations presented herein show that this effect has a strong stabilizing influence on the temperature values near the mesopeak.
Abstract
Radiational heating of the mesosphere results principally from absorption of ultraviolet radiation by ozone. For conditions of photochemical equilibrium, the amount of ozone present near the mesopeak depends critically on the temperature. Relatively high temperature results in less ozone and less heating. Calculations presented herein show that this effect has a strong stabilizing influence on the temperature values near the mesopeak.
Abstract
A simple criterion is presented for determining whether the combined local atmospheric infrared cooling rate at a given height in the presence of two gases, absorbing in the same spectral region, is less than or greater than the cooling rate of either of the gases alone. The criterion is applied to infrared cooling of a tropical atmosphere.
Abstract
A simple criterion is presented for determining whether the combined local atmospheric infrared cooling rate at a given height in the presence of two gases, absorbing in the same spectral region, is less than or greater than the cooling rate of either of the gases alone. The criterion is applied to infrared cooling of a tropical atmosphere.
Abstract
The impact of satellite sounding data on the systematic errors of the numerical weather prediction model of the Israel Meteorological Service has been investigated. In general, satellite data have been shown to reduce systematic error, and in particular, the greatest impact is near where the data have been introduced in the vicinity of low pressure systems.
Abstract
The impact of satellite sounding data on the systematic errors of the numerical weather prediction model of the Israel Meteorological Service has been investigated. In general, satellite data have been shown to reduce systematic error, and in particular, the greatest impact is near where the data have been introduced in the vicinity of low pressure systems.
Abstract
To the extent that the stratosphere wind field is close to geostrophic, the thermal wind is a good approximation to the vertical wind shear (vertical variation of the horizontal wind). And since the thermal wind is proportional to the horizontal temperature gradient, the possibility exists of determining it from satellite radiance observations. Several different methods are developed here for retrieving thermal winds directly from the horizontal gradients of satellite radiance observations, without first retrieving the horizontal temperature gradient. The methods are applied to the determination of thermal winds in the upper troposphere and lower stratosphere over the White Sands Missile Range area. A special series of about 30 concurrent sets of radiance observations from the NDAA-4 VTPR instrument and wind shears from radiosonde observations (for ground truth) distributed throughout one year, is used for these tests. The results obtained with these direct methods are compared with results obtained with 1) a traditional method, in which temperature profiles are first retrieved from the satellite radiances and the thermal winds are then obtained from the horizontal gradients of the retrieved temperatures; and 2) a linear regression between observed radiance gradients and observed wind shears. The latter method serves as an estimate of the upper limit of accuracy to be obtained by any method based on a linear combination of radiance gradients.
The results indicate that the direct methods may be divided into two groups, with much better retrievals for one of these groups. The probable reasons for these differences are identified. The best direct methods yield results comparable to the traditional method. In comparison with ground truth none of the methods is particularly skillful. The lack of skill in these particular cases is attributed mainly to the modest wind shears contained in the sample. Errors associated with trying to measure relatively small horizontal radiance gradients over relatively small horizontal distances result in residual uncertainty nearly as large as the variance of the sample. it is suggested that much better results would be obtained if some of the better methods were to be applied over greater horizontal distances or to regions with larger wind shears.
Abstract
To the extent that the stratosphere wind field is close to geostrophic, the thermal wind is a good approximation to the vertical wind shear (vertical variation of the horizontal wind). And since the thermal wind is proportional to the horizontal temperature gradient, the possibility exists of determining it from satellite radiance observations. Several different methods are developed here for retrieving thermal winds directly from the horizontal gradients of satellite radiance observations, without first retrieving the horizontal temperature gradient. The methods are applied to the determination of thermal winds in the upper troposphere and lower stratosphere over the White Sands Missile Range area. A special series of about 30 concurrent sets of radiance observations from the NDAA-4 VTPR instrument and wind shears from radiosonde observations (for ground truth) distributed throughout one year, is used for these tests. The results obtained with these direct methods are compared with results obtained with 1) a traditional method, in which temperature profiles are first retrieved from the satellite radiances and the thermal winds are then obtained from the horizontal gradients of the retrieved temperatures; and 2) a linear regression between observed radiance gradients and observed wind shears. The latter method serves as an estimate of the upper limit of accuracy to be obtained by any method based on a linear combination of radiance gradients.
The results indicate that the direct methods may be divided into two groups, with much better retrievals for one of these groups. The probable reasons for these differences are identified. The best direct methods yield results comparable to the traditional method. In comparison with ground truth none of the methods is particularly skillful. The lack of skill in these particular cases is attributed mainly to the modest wind shears contained in the sample. Errors associated with trying to measure relatively small horizontal radiance gradients over relatively small horizontal distances result in residual uncertainty nearly as large as the variance of the sample. it is suggested that much better results would be obtained if some of the better methods were to be applied over greater horizontal distances or to regions with larger wind shears.
No Abstract available.
No Abstract available.
