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- Author or Editor: H. Jacobowitz x
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Abstract
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Abstract
A matrix method for multiple-scattering problems, which was the subject of earlier papers, is extended to include the state of polarization in the description of both singly and multiply scattered raditaion. Comparisons of numerical results from the extended matrix method with published values obtained by two other methods are presented (for the special cue of a Rayleigh scattering layer of optical depth τ = 0.25). The values of total intensity (Stokes parameter I) calculated by the matrix method show excellent agreement with published values, while the values of the Stokes parameters Q) and U show slight systematic deviations. For the particular case studied, the numerical results indicate that the inclusion of polarization affects the values of I by less than 10%, and in many cases by less than 17%.
Abstract
A matrix method for multiple-scattering problems, which was the subject of earlier papers, is extended to include the state of polarization in the description of both singly and multiply scattered raditaion. Comparisons of numerical results from the extended matrix method with published values obtained by two other methods are presented (for the special cue of a Rayleigh scattering layer of optical depth τ = 0.25). The values of total intensity (Stokes parameter I) calculated by the matrix method show excellent agreement with published values, while the values of the Stokes parameters Q) and U show slight systematic deviations. For the particular case studied, the numerical results indicate that the inclusion of polarization affects the values of I by less than 10%, and in many cases by less than 17%.
Abstract
Results of calculations of diffuse reflection and transmission of cloud-model layers are presented. These calculations which are based on matrix methods developed by the authors and discussed in a previous paper include the effects of cloud thickness, absorption, drop-size distribution, liquid water content, and directions of the incident and emergent radiation.
Abstract
Results of calculations of diffuse reflection and transmission of cloud-model layers are presented. These calculations which are based on matrix methods developed by the authors and discussed in a previous paper include the effects of cloud thickness, absorption, drop-size distribution, liquid water content, and directions of the incident and emergent radiation.
Abstract
If the radiation field is approximated by a discrete distribution at points or latitude circles on the unit sphere, matrix relationships can be written between incident and reflected or transmitted radiation fields. The reflection and transmission matrices thus defined are shown to satisfy algebraic equations which can be used to compute the properties of thick layers by building up the thick layers from thinner sublayers, the starting point being a layer so thin that it is effectively a single scattering layer only.
Abstract
If the radiation field is approximated by a discrete distribution at points or latitude circles on the unit sphere, matrix relationships can be written between incident and reflected or transmitted radiation fields. The reflection and transmission matrices thus defined are shown to satisfy algebraic equations which can be used to compute the properties of thick layers by building up the thick layers from thinner sublayers, the starting point being a layer so thin that it is effectively a single scattering layer only.
Abstract
A hand-held spectrograph-camera has been used by the Gemini-5 astronauts to obtain spectra of sunlight reflected from clouds in the region of the oxygen “A” band near 7600 Å. The transmittance measurements at selected wavelengths inside the band offered a means of measuring the amount of oxygen in the optical path, and, therefore, the cloud top altitude. Results of the observations are presented, with verification of four cases indicating the validity of the experiment.
A method for computing a correction factor, needed to account for the extra absorption inside the cloud, is developed. This method gives the dependences of the correction factor on the solar zenith, viewing and azimuthal angles. Results of computations by this method are compared with earlier results based on the two-streams theory of Schuster.
Abstract
A hand-held spectrograph-camera has been used by the Gemini-5 astronauts to obtain spectra of sunlight reflected from clouds in the region of the oxygen “A” band near 7600 Å. The transmittance measurements at selected wavelengths inside the band offered a means of measuring the amount of oxygen in the optical path, and, therefore, the cloud top altitude. Results of the observations are presented, with verification of four cases indicating the validity of the experiment.
A method for computing a correction factor, needed to account for the extra absorption inside the cloud, is developed. This method gives the dependences of the correction factor on the solar zenith, viewing and azimuthal angles. Results of computations by this method are compared with earlier results based on the two-streams theory of Schuster.
Abstract
A method for calibrating satellite radiometers is investigated. A calibrated spectral radiometer carried aboard a U2 aircraft at an altitude of 60 000 ft was aligned with White Sands. New Mexico along the same view vector as the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-9 spacecraft at the time of the spacecraft's overpass on 26 August 1985. Both sets of data have been transformed into best estimates of the radiance at satellite altitude inside the footprint of the aircraft radiometer, allowing an estimate of radiance calibration changes in the AVHRR to be made. It is assumed that both instrument systems are linear, that the spectral response function of AVHRR has not changed from its prelaunch value, and that the zero radiance responses of both instruments are accurately known. Extrapolation of the radiances measured from the aircraft to those expected at satellite altitude is achieved by modeling the experimental conditions at White Sands and calculating the ratio of radiances at the two altitudes through the LOWTRAN VI computer program.
Results from data taken within 2 minutes either side of the satellite overpass indicate a 98.9% correlation between the two sets of data, and a change in gain relative to the prelaunch calibration of +2 ± 5% for channel 1 and −2 ± 5% for channel 2 of the NOAA-9 AVHRR. Analysis of other coincident data for the NOAA-9 AVHRR and the aircraft spectral radiometer, including a large dataset from October and November 1986, is now in progress and will establish the day-to-day repeatability of results using this method.
Abstract
A method for calibrating satellite radiometers is investigated. A calibrated spectral radiometer carried aboard a U2 aircraft at an altitude of 60 000 ft was aligned with White Sands. New Mexico along the same view vector as the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-9 spacecraft at the time of the spacecraft's overpass on 26 August 1985. Both sets of data have been transformed into best estimates of the radiance at satellite altitude inside the footprint of the aircraft radiometer, allowing an estimate of radiance calibration changes in the AVHRR to be made. It is assumed that both instrument systems are linear, that the spectral response function of AVHRR has not changed from its prelaunch value, and that the zero radiance responses of both instruments are accurately known. Extrapolation of the radiances measured from the aircraft to those expected at satellite altitude is achieved by modeling the experimental conditions at White Sands and calculating the ratio of radiances at the two altitudes through the LOWTRAN VI computer program.
Results from data taken within 2 minutes either side of the satellite overpass indicate a 98.9% correlation between the two sets of data, and a change in gain relative to the prelaunch calibration of +2 ± 5% for channel 1 and −2 ± 5% for channel 2 of the NOAA-9 AVHRR. Analysis of other coincident data for the NOAA-9 AVHRR and the aircraft spectral radiometer, including a large dataset from October and November 1986, is now in progress and will establish the day-to-day repeatability of results using this method.
Abstract
The Nimbus 6 satellite Earth Radiation Budget (ERB) experiment has continuously monitored the solar radiation input and the reflected shortwave and emitted longwave radiation exitance from the earth-atmosphere system since July 1975. In this paper, the planetary radiation budget parameters observed during the first eighteen months in orbit (July 1975–December 1976) are presented. The results show that the annual mean planetary albedo and longwave radiation flux are 31% and 234 W m−2> (radiative equilibrium temperature of 254 K), respectively. The earth atmosphere system is observed to be in complete radiation balance over a one-year period to within the experimental error of observation. There is an annual cycle of the mean monthly planetary net radiation which is due predominantly to the annual cycle of incoming solar radiation caused by the time variation of earth-sun distance and the sun's declination. Monthly variations in outgoing longwave radiation due to variation in global cloudiness and snow and ice cover are generally compensated by the simultaneous variations in the planetary albedo so that there is generally little monthly variability of the total radiation to space compared to that of the net radiation.
Abstract
The Nimbus 6 satellite Earth Radiation Budget (ERB) experiment has continuously monitored the solar radiation input and the reflected shortwave and emitted longwave radiation exitance from the earth-atmosphere system since July 1975. In this paper, the planetary radiation budget parameters observed during the first eighteen months in orbit (July 1975–December 1976) are presented. The results show that the annual mean planetary albedo and longwave radiation flux are 31% and 234 W m−2> (radiative equilibrium temperature of 254 K), respectively. The earth atmosphere system is observed to be in complete radiation balance over a one-year period to within the experimental error of observation. There is an annual cycle of the mean monthly planetary net radiation which is due predominantly to the annual cycle of incoming solar radiation caused by the time variation of earth-sun distance and the sun's declination. Monthly variations in outgoing longwave radiation due to variation in global cloudiness and snow and ice cover are generally compensated by the simultaneous variations in the planetary albedo so that there is generally little monthly variability of the total radiation to space compared to that of the net radiation.
