pressure, cloudcover, fall could be detected by continuous with an matching s atmospheric Onasmaller the detection world model .scale of an increase in concentration of a particular molecular species (e.g., an SO x pollutant) could also be made by simple comparison. Table 6.2 summarizes possible categories of large-scale spatial niches. Upper atmosphere. Earth's upper atmosphere involves complex chemistry, photochemistry and transport processes. Although significant progress has been made in understanding these processes, there is still a great deal of uncertainty in present knowledge of the stratosphere, mesosphere, and lower thermosphere. The upper atmosphere covers the range of 15 to 150 km in altitude. Absorption and emission of radiation occur over a wide range of the electromagnetic spectrum at these heights. Satellite systems presently exist or are in the planning stages which perform high resolution passive radiometry measurements in both down-looking and limbsounding modes of vibrational (IR) and rotational (mm) molecular transitions. Limb-sounding microwave techniques will for tile first time allow study on a continuous global scale since spectral lines are observed in emission. Micro- TABLE 6.2. POSSIBLE CATEGORIES OF PROPERTIES OF LARGE SCALE SPATIAL NICHES USEFUL FOR EARTH MONITORING
• Humidity profiles • Precipitation location and rates • Air pressure profiles and gradients • Air temperature profiles and gradients • Clouds -cloud top temperature, thickness, height, extent/location, albedo • Atmospheric electrical parameters lightning, magnetospheric electric field • Atmospheric winds • Aerosol size and concentration • Particulate size and concentration • Oxidant levels • Molecular species natural and man-generated CFCI3 HCI CF2C12 HF CF3C1 HN03 CH4 HzO C1ONO2 HN3 CO NO C20 N20 CO2 SO2 03
• Also: Atmospheric transmittance, solar constant, solar flare activity, solar particle detection, Earth
radiation budget wave receiver technology is rapidly advancing to submillimeter wavelengths which will enable the measurement of many additional minor atmospheric constituents that play
a part in radiative transfer processes. Distribution of such constituents is determined by various chemical and photochemical reactions and by atmospheric motions on both small and large scales.
The current research interest in the field of atmospheric studies reflects the present level of understanding of the atmosphere. Of particular importance are measurements improving the knowledge of how man's increasing technological activities may perturb stratospheric processes and
affect the maintenance of the stratospheric ultravioletshielding ozone layer. These upper atmospheric studies require long-term precision composition and thermal measurements.
An understanding of the role of the stratosphere in climatic change and atmospheric evolution is also needed. This includes understanding stratospheric warnings, their impact on chemistry, the spatial distribution of aerosols, and interactions with the troposphere below and the mesosphere above. Measurements of the mesosphere and lower thermosphere are needed to determine composition and variability. Little is known of the basic meteorology in these regions (temperature, pressure, wind variations). Possible variations in 02 in these levels may affect ozone
concentration at lower altitudes. The long-term goal is the development of an intelligent
Earth-sensing information system which can compare synopses of complex nunrerical models of the upper atmosphere with specific observations which are a subset to the original observations required to design those models. Comparisons could be simply the matching of predicted or
acceptable values with observations. The actual models to be flown will have varying degrees of complexity. Most models may just be listings of predicted values derived from complex numerical models. These listings could be compared with observed values (for developmental purposes).
Subsequently, measurements might be reduced to those spectral lines which yield the most information with optimum redundancy. For the purpose of testing systenrs which will be flown on the Titan mission it will be necessary to fly models which are or can be self-modifying to account for any observed discrepancies. St,ice the Earth's atmospheric modeling will be done in much greater detail than is necessary for planetary exploration, tests of adaptive radiative transfer and hydrostatic equilibrium modeling should be kept simple. In planetary exploration, relatively crude remote sensing to determine composition, winds, atmospheric structure, cloud cover, and temperature profiles will be needed to obtain a general understanding of the planet's atmosphere. However, it may be valuable to include complex modeling systems to explicate possible organic chemistries. To reach the required level of understanding of the atmosphere, extensive studies must be undertaken to de
