The global distribution of total ozone: TOMS satellite measurements

The general behavior of total ozone by season and latitude was known before 1930 through the pioneering observations by G. M. B. Dobson. The ozone record at Oxford and other European stations was dominated by an annual cycle and by irregular short term fluctuations. The amplitude and phase of the annual cycle were determined at representative latitudes in both hemispheres. However, the short term variations appeared to be of meteorological origin, although the specific cause could not be identified. Data from the Total Ozone Mapping Spectrometer (TOMS) on the Nimbus 7 spacecraft, with global coverage at an average spatial resolution of 66 km, can now be used to completely map the total ozone field. These maps demonstrate that troughs and ridges in the upper troposphere are responsible for the large, short term ozone variations found at middle latitudes, while in the troplcs, the steady, low ozone levels show broad scale structure associated with the Hadley circulation.     

On the efficiency of polarization measurements while studying aerosols in the terrestrial atmosphere

It has been shown that the orbital polarization measurements of the Earth in the spectral range λ > 300 nm do not allow the sets of the Stokes parameters satisfying the homogeneity requirement for the optical properties of the “atmosphere + surface” system to be retrieved. Due to this, the atmospheric and surface contributions cannot be correctly separated and the physical properties of the atmospheric aerosol cannot be determined. This is caused by the optical heterogeneity of the system, the different nature of aerosol above different relief features, and the poorly predictable temporal changes of the optical properties of the “atmosphere + surface” system. Observations at λ < 300 nm are more acceptable, since not only the surface but also the tropospheric layer of the atmosphere, which are both mostly subjected to the effects of horizontal inhomogeneity and temporal variations, become practically invisible due to a high absorption by the ozone layer. Because of this, from the scans along specified latitude zones, one may obtain the quasi-homogeneous dependences of the second Stokes parameter Q(α) (U(α) = 0) suitable for estimating the physical characteristics of the stratospheric aerosol and revealing their horizontal and temporal variations.     

Atmospheric scattering effects on ground-based measurements of thermospheric winds

Inherent in observations of thermospheric winds from the ground with the Fabry-Perot interferometer is the assumption that the measured Doppler shift is a property of the source medium viewed by the instrumental line of sight. However, ground based airglow observations in regions of weak airglow emission near large intensity gradients may be contaminated by scattered light. Light from areas where the emission is strong can be scattered by the lower atmosphere into the field of view of the observations. Thermospheric winds deduced from the observed Doppler shifts will then show apparent convergence or divergence with respect to the site of observation. Examples of this effect are found in observations by the Michigan Airglow Observatory station located near the auroral zone at Calgary, Alberta. Simulation calculations based upon an experimental model for a significant scattering atmosphere also showed results with either convergence or divergence in the apparent neutral wind field observed by the station.     

SIDRA instrument for measurements of particle fluxes at satellite altitudes. Laboratory prototype

The design concept and first set of results are presented for electronic modules of a laboratory prototype of the small-size satellite instrument SIDRA intended for measurements of charged particle fluxes in outer space. The working prototype consists of a detector assembly based on high-purity silicon and fast scintillation detectors, modules of analogue and digital processing, and a secondary power supply module. The first results are discussed of a Monte-Carlo simulation of the instrument with the use of the GEANT4 toolkit and of measurements of the main parameters of charge-sensitive pre-amplifiers, shapers, and peak detectors. Results of calibration measurements with the use of radioactive sources and beams of accelerated charged particles are presented.     

On the influence of seeing on photospheric velocity measurements

It is shown that the short-period fluctuations of photospheric velocity records can be explained by the scanning effect of atmospheric seeing (image motion) and the velocity gradients present on the solar surface. Some observations supporting this explanation are presented.Mitteilungen aus dem Fraunhofer Institut Nr. 76.     

On determining the ozone number density distribution from OAO-2 stellar occultation measurements

Stellar occultation data from the 2460 Å and 2980 Å channels of the OAO-2 stellar photometers have been used to derive the nighttime ozone number density distribution in the low latitude mesosphere. The nighttime ozone distribution obtained from both channels are similar indicating a maximum in the ozone distribution near 80km of 2–3 × 10³cm^?3.     

The influence of thermospheric winds on exospheric hydrogen on Venus

Monte Carlo models of the distribution of atomic hydrogen in the exosphere of Venus were computed which simulate the effects of thermospheric winds and the production of a “hot” hydrogen component by charge exchange of H⁺ and H and O in the exosphere, as well as classic exospheric processes. A thermosphere wind system that is approximated by a retrograde rotating component with equatorial speed of 100 m/sec superimposed on a diurnal solar tide with cross-terminator day-to-night winds of 200 m/sec is shown to be compatible with the thermospheric hydrogen distribution deduced from Pioneer Venus orbiter measurements.     

Measurements of thermospheric temperatures at a mid-latitude station

Fabry-Perot interferometer measurements of the nightglow 630.0 nm line have been made at Beveridge(37°28′S, 145°6′E) from December 1980 to September 1981.Thermospheric temperatures have been derived from these measurements and compared to the MSIS model. Good agreement is found except during summer when the experimental temperatures are consistently higher (～ 100 K) than the model values. The experimental values are well described by a function similar to that used by Hernandez (1982b) to describe 7 years of data obtained at Fritz Peak which is at a similar mid-latitude to Beveridge. The fit to the Beveridge data indicates larger seasonal and magnetic variations in the temperature than given by the MSIS model.     

Ionospheric measurements from the ESRO-4 satellite

Three ionospheric probes were carried on the ESRO-4 satellite, a spherical gridded probe with swept potential collecting positive ions, a Langmuir probe measuring electron temperature and vehicle potential, and a fixed potential gridded probe measuring fluctuations in total ion density. ESRO-4 was placed in a polar orbit of apogee 1177 km, perigee 245 km on 22 November 1972 and ionospheric data of excellent quality were obtained until the spacecraft's re-entry on 15 April 1974. The instrumentation is described and early results are presented.     

Coronal temperature measurements near a helmet structure base at the 1973 solar eclipse

Observations of coronal Fe XIV emission lines from the NE quadrant during the 1973 solar eclipse are reported. Temperatures are deduced from a pure thermal broadening model, and, in the region near an observed white-light enhancement, an alternative interpretation of halfwidth as being in part due to turbulent velocities is suggested.On leave from the Los Alamos National Laboratory 1981 - present.     

A review of satellite, observations of atmospheric ozone

Since the first satellite ozone measurements in 1960, basically three methods have been developed: backscattered solar ultraviolet, infrared emission, and occultation. In a review article by Krueger et al. (1980, Phil. Trans. R. Soc. Lond. A296, 191), the authors examine the above satellite methods and data covering the period up to about 1980. Our purpose is to review the development of the satellite ozone methodology since about 1980 with particular emphasis on the relationship of satellite data to the continued need for ground-based observations. Finally, we look toward the future to the Upper Atmosphere Research Satellite, to be launched in about 1991, and the view that this is to be a collective experiment, not a series of independent measurements, focusing on the photochemistry and dynamics of the stratosphere.     

Atmospheric scattering effects on ground-based Fabry-Perot measurements of thermospheric winds: An inversion technique

The theoretical development of a technique to recover velocities measured with a Fabry-Perot interferometer in the presence of scattered light is presented. Simulations are carried out which show that the inversion is effective in recovering actual velocities, especially in instances when the observed brightness is dominated by scattered light.     

A model of Titan's aerosols based on measurements made inside the atmosphere

The descent imager/spectral radiometer (DISR) instrument aboard the Huygens probe into the atmosphere of Titan measured the brightness of sunlight using a complement of spectrometers, photometers, and cameras that covered the spectral range from 350 to 1600 nm, looked both upward and downward, and made measurements at altitudes from 150 km to the surface. Measurements from the upward-looking visible and infrared spectrometers are described in Tomasko et al. [2008a. Measurements of methane absorption by the descent imager/spectral radiometer (DISR) during its descent through Titan's atmosphere. Planet. Space Sci., this volume]. Here, we very briefly review the measurements by the violet photometers, the downward-looking visible and infrared spectrometers, and the upward-looking solar aureole (SA) camera. Taken together, the DISR measurements constrain the vertical distribution and wavelength dependence of opacity, single-scattering albedo, and phase function of the aerosols in Titan's atmosphere.Comparison of the inferred aerosol properties with computations of scattering from fractal aggregate particles indicates the size and shape of the aerosols. We find that the aggregates require monomers of radius 0.05 μm or smaller and that the number of monomers in the loose aggregates is roughly 3000 above 60 km. The single-scattering albedo of the aerosols above 140 km altitude is similar to that predicted for some tholins measured in laboratory experiments, although we find that the single-scattering albedo of the aerosols increases with depth into the atmosphere between 140 and 80 km altitude, possibly due to condensation of other gases on the haze particles. The number density of aerosols is about 5/cm³ at 80 km altitude, and decreases with a scale height of 65 km to higher altitudes. The aerosol opacity above 80 km varies as the wavelength to the −2.34 power between 350 and 1600 nm.Between 80 and 30 km the cumulative aerosol opacity increases linearly with increasing depth in the atmosphere. The total aerosol opacity in this altitude range varies as the wavelength to the −1.41 power. The single-scattering phase function of the aerosols in this region is also consistent with the fractal particles found above 60 km.In the lower 30 km of the atmosphere, the wavelength dependence of the aerosol opacity varies as the wavelength to the −0.97 power, much less than at higher altitudes. This suggests that the aerosols here grow to still larger sizes, possibly by incorporation of methane into the aerosols. Here the cumulative opacity also increases linearly with depth, but at some wavelengths the rate is slightly different than above 30 km altitude.For purely fractal particles in the lowest few km, the intensity looking upward opposite to the azimuth of the sun decreases with increasing zenith angle faster than the observations in red light if the single-scattering albedo is assumed constant with altitude at these low altitudes. This discrepancy can be decreased if the single-scattering albedo decreases with altitude in this region. A possible explanation is that the brightest aerosols near 30 km altitude contain significant amounts of methane, and that the decreasing albedo at lower altitudes may reflect the evaporation of some of the methane as the aerosols fall into dryer layers of the atmosphere. An alternative explanation is that there may be spherical particles in the bottom few kilometers of the atmosphere.     

High resolution absorption cross-section measurements of ozone at 195 K in the wavelength region 240–350 nm

Cross-sections of the Hartley-Huggins bands of 03 at the temperature 195 K have been obtained from photoabsorption measurements at column densities in the range 2 × 10¹⁷?1 × 10²¹ cm^?2 throughout the wavelength region 240–350 nm with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines mm^?1 grating and operated at an instrumental width (FWHM) of 0.003 nm. The assumptions made in putting the measured relative cross-sections on an absolute basis are discussed. Fine structure in the cross-section observed in the Huggins bands is illustrated in the region 323–327 nm where shallow features of width 0.01–0.02 nm occur superposed on a stronger apparent continuum exhibiting broader wavy structure.     

An overview of sage I and II ozone measurements

The Stratospheric Aerosol and Gas Experiments (SAGE) I and II measure Mie, Rayleigh, and gaseous extinction profiles using the solar occultation technique. These global measurements yield ozone profiles with a vertical resolution of 1 km which have been routinely obtained for the periods from February 1979 to November 1981 (SAGE I) and October 1984 to the present (SAGE II). The long-term periodic behavior of the measured ozone is presented as well as case studies of the observed short-term spatial and temporal variability.

A linear regression shows annual, semi-annual, and quasi-biennial oscillation (QBO) features at various altitudes and latitudes which, in general, agree with past work. Also, ozone, aerosol, and water vapor data are described for the Antarctic springtime showing large variation relative to the vortex. Cross-sections in latitude and altitude and polar plots at various altitudes clearly delineate the ozone hole vertically and areally. Comparisons of vertical profiles are made from 1979 to 1988.

Although there is a three-year gap between the SAGE I and II measurements, the two data sets have been used to determine long-term changes in ozone. The intercomparison generally shows decreases in the upper stratosphere (25–50 km) of 4% or less from 1980 to 1986.     

Possible flyby measurements of Galilean satellite interior structure

Flyby encounters of the Galilean satellites from a Jupiter orbiter spacecraft could yield information about the second-degree gravity harmonics of these satellites. We have calculated the expected values of these harmonics for a range of plausible interior models in hydrostatic equilibrium. Because the satellites respond to comparable perturbations from rotation and tides, an independent test of hydrostatic equilibrium is feasible. For Io and Ganymede, the expected measurement accuracy from a nominal encounter should make possible an excellent discrimination from the ensemble of interior models. For Europa, a qualitative distinction between near-uniform and centrally condensed models seems feasible. Only for Callisto is the proposed experiment of marginal value.     

On the artificial satellite theory

Some of the basic ideas of an analytical orbiter theory which is being developed by Hubert Claes in Namur are presented.The theory is based on the Lie transform technique and will be expressed in a closed form up to second order. The inclusion of additional terms of the third order (expanded in power series of the eccentricity) will be considered.Special attention is being given to the choice of the elements and to the final form of the theory. Three main criteria are used. The removal of the virtual singularities of small inclination and eccentricity. The simplicity of the final form of the theory once the elements have been given their numerical values. The numerical stability of the evaluation of the theory.     

Discussion of the 60 year total ozone record at Arosa based on measurements of the vertical distribution and a meteorological parameter

On G. M. B. Dobson's initiative, ozone measurements were started by Götz at Arosa, Switzerland, in 1926, which led to the longest total ozone record in the world over 60 years. Later these measurements were supplemented by Umkehr observations, also at Arosa, and by ozone soundings at Payerne, Switzerland, yielding the concurrent vertical distribution which allows among other things to distinguish between regional and hemispheric scale processes influencing total ozone. Using a meteorogical parameter a method is developed which allows the extension of this distinction to the early period without measurements of the vertical distribution, although with somewhat larger uncertainty. On this basis the ozone variations over Arosa during the past 60 years are discussed.

The ozone loss around the level of the ozone maximum contributed most to the strong decline in the total amount observed between 1970 and 1988. High loss rates were further detected in the upper stratosphere, extending down into the middle stratosphere. While the upper stratospheric decrease is very probably largely a consequence of the CFC input into the atmosphere the loss at the lower level seems to be only partly due to that reason, but in its main contribution to be produced by circulation changes. About one-third of the stratospheric ozone decline is compensated by rapidly rising concentrations in the troposphere caused by increasing air pollution.