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- Author or Editor: D. Q. Wark x
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Abstract
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Abstract
A new approach is presented to the problem of specifying constraints on retrieval estimators used to calculate vertical temperature profiles from satellite measurements of upwelling radiance. An unsupervised classification scheme determines the typical shapes of temperature profiles that represent meteorologically significant events in some large ensemble of profiles. A data base for this purpose is developed, and a set of typical shape functions (TSFs) calculated to represent the sample. The TSFs are used to specify a radiance classifier which, given a radiance observation, defines the TSF class and thereby the constraints upon the retrieval estimator. An example is given, using simulated 15 μm data for the NOAA-6 TOVS. Preliminary calculations with synthetic radiance data indicate that an optimum inverse retrieval estimator using TSF-defined constraints results in rms differences that are approximately 50% better than those for a truncated eigenvector expansion regression estimator using zonally defined statistics; improvement in the region of the midlatitude tropopause is greater than 50%.
Abstract
A new approach is presented to the problem of specifying constraints on retrieval estimators used to calculate vertical temperature profiles from satellite measurements of upwelling radiance. An unsupervised classification scheme determines the typical shapes of temperature profiles that represent meteorologically significant events in some large ensemble of profiles. A data base for this purpose is developed, and a set of typical shape functions (TSFs) calculated to represent the sample. The TSFs are used to specify a radiance classifier which, given a radiance observation, defines the TSF class and thereby the constraints upon the retrieval estimator. An example is given, using simulated 15 μm data for the NOAA-6 TOVS. Preliminary calculations with synthetic radiance data indicate that an optimum inverse retrieval estimator using TSF-defined constraints results in rms differences that are approximately 50% better than those for a truncated eigenvector expansion regression estimator using zonally defined statistics; improvement in the region of the midlatitude tropopause is greater than 50%.
Abstract
The infrared radiance data obtained from measurements by the TIROS satellites have been used to deduce the limb darkening. Large numbers of data permit a statistical treatment in a matrix of radiance and local zenith angle. It is found that, on the average, the degree of limb darkening is largely independent of the absolute value of radiance. However, examination of the limb darkening as a function of latitude and season shows a significant variation which is related in an unresolved way to the surface and atmospheric temperatures, and to the types and amounts of clouds. An empirical expression is developed to generalize the radiances in terms of the local zenith angle, the latitude and the time of year.
Abstract
The infrared radiance data obtained from measurements by the TIROS satellites have been used to deduce the limb darkening. Large numbers of data permit a statistical treatment in a matrix of radiance and local zenith angle. It is found that, on the average, the degree of limb darkening is largely independent of the absolute value of radiance. However, examination of the limb darkening as a function of latitude and season shows a significant variation which is related in an unresolved way to the surface and atmospheric temperatures, and to the types and amounts of clouds. An empirical expression is developed to generalize the radiances in terms of the local zenith angle, the latitude and the time of year.
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
TIROS I pictures of the Gulf of St. Lawrence, taken during the first days after launch, have clearly revealed areas of ice. The ice patterns found in two series of pictures are mapped. Also shown are aircraft observations of ice made a week earlier and a week later. The results indicate that observations from satellites might contribute to ice surveys.
Abstract
TIROS I pictures of the Gulf of St. Lawrence, taken during the first days after launch, have clearly revealed areas of ice. The ice patterns found in two series of pictures are mapped. Also shown are aircraft observations of ice made a week earlier and a week later. The results indicate that observations from satellites might contribute to ice surveys.
Abstract
The statistical minimum-rms inversion method used to obtain temperature profiles, requires estimates of covariance matrices and means for Planck function profiles of the atmosphere. In order to obtain these estimates over the pressure range of IWO to 0.01 mb, it was necessary to combine data from temperature measurements by radiosondes, rocketsondes and grenadesondes. Radiosonde data reaching the 10-mb level were extended to higher levels by means of a modified regression technique. Matrices and means have been obtained by this method for seasonal and geographical groupings in the Northern Hemisphere and the tropics. Details of the geographical and time changes in the matrices and the means are presented.
Abstract
The statistical minimum-rms inversion method used to obtain temperature profiles, requires estimates of covariance matrices and means for Planck function profiles of the atmosphere. In order to obtain these estimates over the pressure range of IWO to 0.01 mb, it was necessary to combine data from temperature measurements by radiosondes, rocketsondes and grenadesondes. Radiosonde data reaching the 10-mb level were extended to higher levels by means of a modified regression technique. Matrices and means have been obtained by this method for seasonal and geographical groupings in the Northern Hemisphere and the tropics. Details of the geographical and time changes in the matrices and the means are presented.
Abstract
The balloon model of the Satellite Infrared Spectrometer has been flown with balloons at altitudes of about 30 km. from Palestine, Tex. and Sioux Falls, S. Dak. The instrument was calibrated in flight by reference to an internal blackbody at a measured temperature; radiances were deduced for each of the six intervals in the 15-µ band and the interval at 11.1µ in the window. During the Palestine flight the balloon passed over clear areas and over cumulonimbus clouds whose tops were at about 250 mb. From data in each area, the vertical temperature profile was deduced and compared with radiosonde data; in the cloudy areas the profile was limited to the region above the clouds. From data in the 11.1-µ channel, surface temperatures were deduced; the temperatures, corrected for atmospheric water vapor, were compared with special surface temperature measurements and with screen temperatures from Weather Bureau stations. Because of strong radio frequency interference, the 15-µ channels of the Sioux Falls flight were of reduced quality and it was possible to retrieve only a few data for the temperature profile; however, the 11.1-µ data were satisfactory for good surface temperature determination.
Abstract
The balloon model of the Satellite Infrared Spectrometer has been flown with balloons at altitudes of about 30 km. from Palestine, Tex. and Sioux Falls, S. Dak. The instrument was calibrated in flight by reference to an internal blackbody at a measured temperature; radiances were deduced for each of the six intervals in the 15-µ band and the interval at 11.1µ in the window. During the Palestine flight the balloon passed over clear areas and over cumulonimbus clouds whose tops were at about 250 mb. From data in each area, the vertical temperature profile was deduced and compared with radiosonde data; in the cloudy areas the profile was limited to the region above the clouds. From data in the 11.1-µ channel, surface temperatures were deduced; the temperatures, corrected for atmospheric water vapor, were compared with special surface temperature measurements and with screen temperatures from Weather Bureau stations. Because of strong radio frequency interference, the 15-µ channels of the Sioux Falls flight were of reduced quality and it was possible to retrieve only a few data for the temperature profile; however, the 11.1-µ data were satisfactory for good surface temperature determination.
Abstract
The TIROS II meteorological satellite carried a multiple channel radiometer of medium resolution (about 5 deg). Two of the channels were designed to measure the upward radiation in the “window” at 8–12 microns, and over the broad spectral region of 7–30 microns. To deduce surface temperatures and total upward flux values from the measurements in these two channels, additional operations must be carried out on the data. As a basis for these transformations, the specific spectral intensity over the entire infrared region was calculated at five zenith angles for each of 106 atmospheric models. In the 7–30 micron channel, an empirical relation was found to transform measured values to total intensity; and, from the limb-darkening exhibited by the 106 individual models, a method of calculating flux was formulated; in this case, the results contain inaccuracies of only about two per cent attributable to the method used. In the 8–12 micron channel, the influence of ozone and water vapor was determined for the model atmospheres, and curves were developed for the direct transformation from measured values to surface temperature; however, if a knowledge of the water vapor content of the viewed column is lacking, errors in the inferred surface temperature can range from near zero to 10 deg or more. A series of radiative flux maps over Europe, calculated from the 7–30 micron data, have values whose magnitudes are in accord with other estimates and measurements. Corrected satellite 8–12 micron data are compared with shelter temperatures for several stations in a cloudless area; the range of the satellite data from 3.5 deg higher to 5.0 deg lower than the shelter data is discussed.
Abstract
The TIROS II meteorological satellite carried a multiple channel radiometer of medium resolution (about 5 deg). Two of the channels were designed to measure the upward radiation in the “window” at 8–12 microns, and over the broad spectral region of 7–30 microns. To deduce surface temperatures and total upward flux values from the measurements in these two channels, additional operations must be carried out on the data. As a basis for these transformations, the specific spectral intensity over the entire infrared region was calculated at five zenith angles for each of 106 atmospheric models. In the 7–30 micron channel, an empirical relation was found to transform measured values to total intensity; and, from the limb-darkening exhibited by the 106 individual models, a method of calculating flux was formulated; in this case, the results contain inaccuracies of only about two per cent attributable to the method used. In the 8–12 micron channel, the influence of ozone and water vapor was determined for the model atmospheres, and curves were developed for the direct transformation from measured values to surface temperature; however, if a knowledge of the water vapor content of the viewed column is lacking, errors in the inferred surface temperature can range from near zero to 10 deg or more. A series of radiative flux maps over Europe, calculated from the 7–30 micron data, have values whose magnitudes are in accord with other estimates and measurements. Corrected satellite 8–12 micron data are compared with shelter temperatures for several stations in a cloudless area; the range of the satellite data from 3.5 deg higher to 5.0 deg lower than the shelter data is discussed.
