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F. W. Taylor

Abstract

The infrared absorption spectrum of solid ammonia is obtained from 2 to 125 μm as a composite of the published measurements. From this, the absorption coefficient and the complex refractive index are calculated as a function of frequency by integration of the Kramers-Krönig dispersion relations. These data are used in a Mie theory analysis to obtain the basic parameters for scattering of long wavelength radiation by solid ammonia particles; this is believed to be an important process in radiative transfer within the atmospheres of the giant planets.

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F. W. Taylor

Abstract

The infrared radiometer experiment on Mariner 10 measured limb darkening curves for Venus in two spectral intervals, one near 11 µm and the other near 45 µm. In this paper, these are analyzed in terms of the vertical opacity profile at each wavelength over a limited altitude range, approximately 60–80 km above the surface of the planet. Accurate multiple scattering calculations are used to show that both opacity profiles are consistent with a model containing a cloud of 1.1 µm radius sulphuric acid droplets, and a small amount of water vapor. Profiles of particle number density and humidity vs height are presented.

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F. W. Taylor

Abstract

The possibilities for vertical temperature sounding experiments by medium-resolution measurements of outgoing radiance are examined for non-scattering models of Jupiter, Saturn, Uranus and Neptune. It is shown that for Jupiter the widest vertical coverage of the atmosphere results from five or six channels placed in the ν4 band of methane at 7.5 μ, but energy constraints render this experiment marginal at Saturn and useless at Uranus and Neptune. For the outermost planets, the best experiment is three or four channels located in the long-wavelength half of the pressure-induced S(O) line of hydrogen, in the range 25–40 μ with which a limited vertical range of about two scale heights can be covered. Some results of inversion of synthetic data are presented in each case, and the likely effect of clouds on the measurements is discussed.

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J. T. Houghton and F. W. Taylor

Abstract

Some of the possibilities for remote sensing of the upper atmosphere of Venus from an orbiting spacecraft are studied quantitatively. Temperature sounding over a wide vertical range, from the main cloud top near 60 km altitude to the nanobar level near 160 km, is shown to be feasible. Techniques which deconvolve the c1oud structure from the temperature profile measurements are examined. Humidity measurements by simple radiometry are feasible for column abundances ≳10 precipitable micrometers. The information content of limb radiance measurements, in different wavelengths and for various viewing geometries, is also analysed.

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M. T. Chahine, H. H. Aumann, and F. W. Taylor

Abstract

The cloud-filtering technique developed in Parts I and II of this study is experimentally verified in this paper. The verification is based on radiance data measured in the 4.3 and 15 µm bands using a multi-detector sounder mounted on an aircraft. The results presented here show that, from the aircraft height of 7.6 km and in the presence of multiple cloud formations, it is possible to recover simultaneously:

  1. The clear-column atmospheric temperature profile with an rms error of 1 K with respect to radiosondes.

  2. The land and sea surface temperature at all sun zenith angles. The accuracy of the recovered sea-surface temperature is 0.5-1 K with respect to measured bucket temperatures.

  3. The humidity profile (water vapor mixing ratio) with a precision of 10%.

  4. The fractional covers and heights of up to three cloud formations.

  5. The types of clouds, i.e., whether convective or nonconvective.

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M. López-Puertas, M. A. López-Valverde, and F. W. Taylor

Abstract

Solar heating and thermal cooling rates by the CO2 near-infrared bands in the mesosphere and lower thermosphere are derived from measurements of the CO2 4.3 μm atmospheric emission by the Stratospheric and Mesospheric Sounder on Nimbus 7. A detailed analysis of the relaxation of the solar energy initially absorbed by the different bands, before it escapes to space or is thermalized, is included. The isotopic and hot bands of CO2 near 4.3 μm play an important role since they produce a significant heating in the mesosphere and are important emitters of the solar energy absorbed at 4.3 μm and 2.7 μm around the mesopause. The pathways followed by the fraction of the electronic energy of O(1D) that is transferred into the CO2(00°1)-N2(1) system have been studied, resulting that an important fraction of this energy is emitted by the CO2 4.3 μm fundamental band in the lower thermosphere. Sensitivity studies of the net heating rates to the atomic oxygen and carbon dioxide concentrations and to the rate of vibrational energy transfer are also presented. Global distributions of solar heating rates by CO2 for solstice and equinox situations are shown. They present a double peak structure with maxima situated around 95 and 75 km; the latter being particularly important because other components of the radiative balance have at a minimum at the same region.

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F. W. Taylor, A. Lambert, R. G. Grainger, C. D. Rodgers, and J. J. Remedios

Abstract

Observations of polar stratospheric clouds by the Improved Stratospheric and Mesospheric Sounder (ISAMS) experiment on the Upper Atmospheric Research Satellite (UARS) have revealed new details of their global properties and behavior. These include the vertical and horizontal spatial distributions of Arctic and Antarctic polar stratospheric clouds (PSCs) as a function of time and air temperature, their optical thicknesses and estimated densities, their spectral properties, and their inferred composition. In particular, ISAMS spectral data allows different PSC types to be distinguished from each other and from volcanic aerosol by their compositional differences. Northern PSCs during the 1991/92 season are found to be more ephemeral and more compact than reported in previous years and to differ markedly in scale from those in the Southern Hemisphere, which cause the Antarctic ozone hole by activating stratospheric chlorine chemistry. There were only two episodes of dense PSC formation in the 1991/92 northern winter, one of which took place in sunlight. The latter correlates well with UARS/Microwave Limb Sounder observations of enhanced chlorine monoxide, but substantial amounts of chlorine monoxide were also reported at times and places with at most very minor PSC activity.

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Rowan T. Sutton, Hector Maclean, Richard Swinbank, Alan O'Neill, and F. W. Taylor

Abstract

A technique is introduced by which high-resolution tracer fields may be constructed from low-resolution satellite observations. The technique relies upon the continual cascade of tracer variance from large to small scales and makes use of wind fields generated by a data assimilation scheme. To demonstrate its usefulness, the technique has been applied in a study of isentropic distributions of nitrous oxide in the winter midstratosphere, using measurements made by the Improved Stratospheric and Mesospheric Sounder instrument on the Upper Atmosphere Research Satellite. The results show that the high-resolution fields significantly increase the amount of information that is available from the satellite observations. The fields give insights into the characteristic structure and evolution of tracer distributions at scales that are normally obscured from view. Two results are particularly noteworthy. First, at the interface between low and middle latitudes there is evidence of active mixing. This mixing occurs on the eastern, equatorward side of air that is being drawn toward high latitudes around the polar vortex. Second, in the anticyclone, a complex pattern of transport is revealed. Air drawn in from low latitudes spirals together with ambient midlatitude air. Small scales are generated relatively slowly in the organized flow, and persistent filamentary structures, with transverse scales of hundreds of kilometers or greater, are seen.

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S. L. Ruth, J. J. Remedios, B. N. Lawrence, and F. W. Taylor

Abstract

Measurements of stratospheric nitrous oxide made by the Improved Stratospheric and Mesospheric Sounder (ISAMS) during the period 28 October 1991–18 January 1992 are presented. The data are consistent with the dynamical fields at the time, and are in extremely good qualitative agreement with similar data from the Nimbus-7 SAMS and the Upper Atmosphere Research Satellite (UARS) Cryogenic Limb Array Etalon Spectrometer (CLAES) instruments, although in some regions the values are higher than have been obtained elsewhere. A major problem in the retrieval of the data has been contamination of the measured signal by aerosol emitted during the Mount Pinatubo eruption of June 1991. Despite the uncertainty in the values, the ISAMS N2O measurements provide a unique opportunity to study the synoptic evolution of a long-lived chemical tracer throughout the early winter, with near-continuous high-resolution measurements. The zonally averaged data are shown, as well as the measurements in the Northern Hemisphere on the 1150-K isentropic surface, with reference to temperature and wind fields from the same period derived also from ISAMS measurements. Finally, along-track cross sections are shown, which illustrate in greater detail the vertical and horizontal structure of the northern winter vortex region.

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S. M. Rosier, B. N. Lawrence, D. G. Andrews, and F. W. Taylor

Abstract

Dynamical fields based on temperature measurements from the Improved Stratospheric and Mesospheric Sounder on the Upper Atmosphere Research Satellite are presented for the Northern Hemisphere stratosphere for the period 28 October 1991 through 18 January 1992. Interpretation of these fields gives a picture of the dynamical evolution of this period in terms of the zonal-mean fields and the synoptic structures. Among the features of interest are the movements of the zonal-mean jets and several periods of stratospheric warming, culminating in a near-major warming in January.

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