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This document is a viewgraph presentation which reviews the progress in the X-34 Project. The X-34 program demonstrates the technologies and operations required to develop the next generation of reusable launch vehicles. The presentation includes descriptions and design views of the vehicle. It reviews features of the MC-1 (i.e. Fastrac Engine), and the propulsion system. It also includes information about the thermal protection system.
An analysis is presented of the long-term mean pressure-latitude seasonal distribution of tropospheric and lower stratospheric ozone for the four seasons covering, in part, over 20 years of ozonesonde data. The observed patterns show minimum ozone mixing ratios in the equatorial and tropical troposphere except in regions where net photochemical production is dominant. In the middle and upper troposphere, and low stratosphere to 50 mb, ozone increases from the tropics to subpolar latitudes of both hemispheres. In mid stratosphere, the ozone mixing ratio is a maximum over the tropics. The observed vertical ozone gradient is small in the troposphere but increases rapidly above the tropopause. The amplitude of the annual variation increases from a minimum in the tropics to a maximum in polar regions. Also, the amplitude increases with height at all latitudes up to about 30 mb where the phase of the annual variation changes abruptly. The phase of the annual variation is during spring in the boundary layer, summer in mid troposphere, and spring in the upper troposhere and lower stratosphere.
Solar Lyman alpha irradiance is estimated from various solar indices using linear regression analyses. Models developed with multiple linear regression analysis, including daily values and 81-day running means of solar indices, predict reasonably well both the short- and long-term variations observed in Lyman alpha. It is shown that the full disk equivalent width of the He line at 1083 nm offers the best proxy for Lyman alpha, and that the total irradiance corrected for sunspot effect also has a high correlation with Lyman alpha.
It is pointed out that both the total amount and the vertical distribution of atmospheric ozone are presently measured routinely by various ground-based and satellite-borne instruments and by instruments mounted on different carrier platforms such as balloons, aircraft, and rockets. The techniques of observing atmospheric ozone are discussed, taking into account the determination of total ozone, the Dobson spectrophotometer, the Brewer spectrophotometer, the M-83 Filter Ozonometer, and satellite techniques. In a discussion of studies of vertical distribution, remote systems are considered along with in situ measurements. Attention is given to ground-based methods, satellite platforms, backscatter measurements, limb observations, electrochemical methods, chemiluminescent methods, optical methods, and rocket observations. A number of graphs showing the observed distribution of atmospheric ozone are also presented, and changes in this distribution are evaluated.
An instrument on the Solar Mesosphere Explorer has been making daily solar irradiance measurements in the 120-305 nm (UV) spectral interval since October 6, 1981. Calculations of the highest to lowest value of the irradiance within each solar rotation yield percent range values indicative of variations that are useful as input data for model calculations of stratosphere/mesosphere responses to short period solar variability, since solar radiation in the UV is largely responsible for the photochemical interactions and radiative heating of the stratosphere, mesosphere, and lower thermosphere.
It is noted that the region of strongest relationship between tropical stratospheric zonal winds and total ozone (that is, maximum ozone associated with strong west winds) is in the tropics, in the midlatitudes of the Southern Hemisphere, and, it is thought, at high latitudes of the Northern Hemisphere. The observed period of the ozone quasi-biennial oscillation (QBO) decreases from 27 months at the equator to approximately 24 months in midlatitudes, possibly due to local modification of the QBO, as it propagates poleward. In the tropics the ozone variation is seen to be nearly in phase with the tropical wind QBO while at middle and high latitudes of the Northern Hemisphere and midlatitudes of the Southern Hemisphere and ozone oscillation seems to lag the wind oscillation by about 12-14 months. The out-of-phase relationship at middle and high latitudes indicates a possible interaction between the tropical stratosphere QBO in zonal winds and the annual variation in the poleward transport of ozone by quasi-horizontal eddies.
Umkehr, ozonesonde and satellite observations are used to determine the height/latitude distribution of the amplitude and phase of the periodic components of the variation in the ozone mixing ratio in the middle and upper stratosphere. The amplitude of the first (annual) harmonic is found to be small in the subtropics and to increase to a maximum at polar latitudes. In addition, it increases with height in the mid and upper stratosphere to an apparent maximum just below the stratosphere. The second (semi-annual) harmonic possesses an amplitude that is largest in tropical regions and in subpolar regions at a level of about 40 km. Very little ozone variation is seen above 30 km with dominant periods close to the quasi-biennial period of total ozone observed in the tropics. The percentage of the total variance of the ozone mixing ratio accounted for by the first harmonic is found to be larger than 60 percent at all heights from 20 deg to 60 deg latitude in both hemispheres (except near 40 km in the Northern Hemisphere).
The degree of association between total and stratospheric ozone and solar ultraviolet irradiance is evaluated based on mean monthly latitudinally averaged ozone observations from the Nimbus-4 BUV data set. The mean monthly 10.7 cm solar flux f(10.7), adjusted for varying earth-sun distance, is used as a convenient index of solar UV variation. Results show no obvious relationship between total ozone and solar ultraviolet irradiance based on analysis of satellite data over a period of seven years, even though such a relationship has been suggested from theoretical considerations. However, the analysis does indicate that there may be a positive response in the upper tropical stratosphere, at a height of about 45-50 km such that there is an increase in the ozone concentration following an increase in solar UV radiation, which is assumed to be indicated by an increase in f(10.7) flux
Latitude-height cross sections of the mass mixing ration are shown for two different years for equinoctial and Northern Hemisphere winter periods. The data represent two week averages for October 1967 and 1968, and for January 1958 and 1969. For October 1967, the ozone distribution is symmetrical about the equator although the values are higher in the Southern Hemisphere (spring) and about 30-35 km. In October 1968, the distribution about the equator is quite symmetrical. The latitudinal variation at levels above about 3 mb (40 km) is small where photochemical processes are dominant in determining the ozone distribution. In 1967, there is a slight increase at these levels towards the poles that reflect a temperature influence in the ozone chemistry in the upper stratosphere. This increase, however, is absent in 1968.
Examination of the relationship between tropical stratosphere zonal wind and ozone indicate a variable response in latitude with Northern Hemisphere tropics and polar regions and Southern Hemisphere mid-latitudes showing the strongest response with relatively weaker response at Northern Hemisphere mid-latitudes and the Southern Hemisphere tropics. In tropical regions, the west winds and ozone maxima are in phase while at higher latitudes, a more nearly out-of-phase relationship prevails. At subtropical and middle latitudes, the QBO in ozone does not appear to change phases with altitude. These features are suggestive of an interaction between the tropical zonal winds and poleward transport of horizontal eddies in conjunction with the annual poleward transport of ozone.
The mean monthly hemispheric total ozone values as determined from between the two sets of data indicates that the mean difference between the calculated total ozone amount as determined for the entire period from all the satellite data and that derived from the satellite data restricted to location of ground based stations is 1.3 m atm cm for the Northern Hemisphere and 0.7 m atm cm for the Southern Hemisphere (0.3 and 0.2 percent respectively of the average total ozone in each hemisphere).
Recent developments in observational techniques are examined, taking into account a review of some unresolved problems in the measurement/estimation of total ozone and the vertical ozone profile, the sensitivity of Dobson total ozone estimations to wavelength band calibration uncertainties, errors in Dobson total measurements arising from aerosol attenuation, and optical stop and focussing effects in the Dobson instrument. Other subjects considered are related to total ozone observations, tropospheric ozone, upper air ozone observations, observations of trace gases in the atmosphere, ozone photochemistry and directly related photochemical models, the interaction of ozone and atmospheric circulation, ozone effects on climate, and solar activity and ozone variations. Programs and recommendations involving ozone theory and observations are also discussed, giving attention to current problems of ozone chemistry, the upper atmosphere research satellite program, a French contribution to ozone related studies, and ozone and the middle atmosphere program.
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Analyses are presented of the association between two parameters of solar activity (Lyman-alpha and 10.7 cm flux) and global total ozone as determined from Nimbus observations for the period April-December 1970 (IRIS observations), and April 1970-April 1972 (BUV observations); and between Lyman-alpha and global total ozone as observed at ground stations and the ozone concentration in the lower and middle stratosphere in the subtropics for the period 1969-1972. It is shown that the high correlations discussed in other published studies between these solar paramters and nine months of IRIS data resulted from the use of a very limited, seasonally unfiltered data set.
Total ozone observations in the international network have been used as a basis for the analysis of the mean monthly ozone distribution over the globe for the period 1957-1975. It has been found that during the period 1961-1970 the total ozone amount increased in the Northern Hemisphere by about 12 percent and that this increase seems to be significant at all latitudes. Although the data were sparse for the Southern Hemisphere, there did not appear to be any significant ozone changes during the 10 year period. Relatively large geographic variations were found in the ozone trends and it is suggested that these variations are related to large scale changes in the atmospheric circular pattern.
Observations of total ozone at a number of stations in the Northern Hemisphere show an increase during the period 1961-1970 followed by a decrease of ozone during the 1970's, at least at many stations in Central Europe. It is well known that total ozone is highly correlated with ozone in the lower stratosphere. Analysis of the trends of ozone based on data derived from balloon-borne ozonesondes during the period 1967-75 at four stations in Central Europe shows that most of the ozone variations occurred in the lower stratosphere with relatively little contribution from tropospheric changes or those above the ozone peak. Possible meteorological origins of these decade type variations will be discussed.
The total amount of ozone in a vertical column has been measured spectroscopically at near ultraviolet and visible wavelengths, using ground- and satellite-based instruments. The vertical distribution of ozone from the surface up to approximately 100 km has been measured by a variety of techniques - chemical and optical - and from a number of observing platforms, including balloon, rocket, and satellite platforms. The various methods presently used for determining the atmospheric ozone distribution are reviewed, along with a discussion of their advantages and disadvantages. The observed average distribution of total ozone for the period 1958-1975 shows the expected geographic and seasonal variations. The variations of total ozone, including hemispheric differences, are clearly associated with large-scale circulation processes in the lower stratosphere. Approximately ten years of observations of the vertical ozone distribution, up through the ozone maximum, also show geographic and seasonal variations strongly related to the lower stratosphere circulation. The distribution above the maximum, however, results from the interaction of photochemistry and stratospheric motions.