Since the equilibrium concentration lines are essentially vertical at 100, 000 feet, the range of concentration at this altitude was used to estimate the expected concentrations shown in Table 1. It should be pointed out that studies of departure from equilibrium require that observations be made with greater precision than when examining the movement of tracers. Overall errors of collection and counting would have to be much less than 10 percent for meaningful meteorological interpretation. Stable Elements and Compounds sampling of stable elements and compounds above 100, 000 feet can also be of great importance in providing information about the atmosphere. Tabie 2 lists a few of the substances of interest. TABLE 2 STABLE ELEMENTS AND COMPOUNDS ABOVE 100, 000 FEET Substance Amount needed co, 10°? cc at NTP 300 ppm 0.03 HO 10° gm H,O 10° gm/kg - 1 gm/kg 300 - 0.3 0-16/0-18 10°? gm HO H-2/H-1 10 Carbon Dioxide. -3 Expected values SCF required 3x 10° - 30 4 3x10 - 30 gm H,0 Carbon dioxide abundance measurements are of particular interest. The addition of CO, to the lower atmosphere resulting from our increasing industrialization may be reflected in a gradient of co, in the upper atmosphere. Attempts to measure this gradient have been unsuccessful. Figure 8 shows the results of measurements made from balloon samples as several altitudes and latitudes (different symbois). horizontal lines show limits of uncertainty in individual observations. cerning the gradient of CO, techniques are needed. 2 The It is evident that no conclusions con- abundance between 40,000 and 100, 000 feet can be drawn and that more precise A great advantage of having CO, abundance data in future samples would be in providing an accurate estimate of the volume of air sampled. Water Vapor, ure 9), There is a tremendous interest in the water vapor content of the high atmosphere (Fig- The British meteorological research flights (M.R.F.) have clearly shown the persistence of a very dry layer between 45, 000 and 50, 000 feet from the latitude of Britain to the tropics. This was explained by the very cold upper tropospheric temperatures in the tropics wringing the moisture from ascending currents. Measure- ments at much higher altitudes by freeze-out traps on balloons (Barclay) and by spectroscopic observation giving mean values through thick layers (vertical lines) all indicate an increase in the water vapor mixing ratio with altitude above about 50,000 feet. Stable Isotope Ratios. The source of this water is at present a meteorological mystery. There has been considerable recent work on relating the ratios of stable oxygen (0-16/0-18) and hydrogen (H-2/H-1) to the sources of moisture and the conditions surrounding the evaporation and condensation cycles experienced. high atmosphere, 36 Data on these ratios may be of value in unravelling the mysteries of the