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Applied Optics Letters to the Editor Letters to the Editor should be addressed to the Editor, APPLIED OPTICS, 1155 16th St., N.W., Washington 6, B.C. Mean Atmospheric Moisture Profiles to 31 km for Middle Latitudes Murray Gutnick Meteorological Development Laboratory, Air Force Cambridge Research Laboratories, Bedford, Massachusetts. Received 1 June 1962. Average yearly vertical profiles up to 31 km in middle latitudes of mixing ratio and dewpoint-frostpoint, derived independently, are presented in a table and a figure. Also, since the relation between mixing ratio and frostpoint is nonlinear, other moisture expressions were derived from each of the basic profiles, using Standard Atmosphere conditions. Up to 7 km the basic profiles were developed from conventional radiosonde humidity measure- ments; above that level they are based upon experimental humidity ascents, subjectively selected and weighted. The annual mid-latitude mixing ratio profile decreases from 6150 ppm (mg/kg) at the surface to 9 ppm at 16 km, then in- creases slightly with height; the surface dewpoint is taken at 4°C, decreasing to 78°C at 18 km, then increasing 0.5 deg/km. This letter is a brief summary of a comprehensive study 1 pre- senting preliminary models of the variation of atmospheric moisture with height. The concept is similar to that of other standard atmospheres. The paucity and ambiguity of upper-air moisture data make the models offered here quite crude. As observations increase, the models can be revised, refined, and extended evolving in the same way as other representations of atmospheric structure. The tropospheric portion of the mixing ratio profile was derived by estimating, from recent maps, the mean annual pre- cipitable water above each of four widely separated surfaces at 45°N. The corresponding mean mixing ratios were assumed to be those of two stations having the same precipitable water as the derived mean annual values. The stratospheric portion of the mixing ratio profile is a weighted average of the best soundings from each of half-a-dozen sets of experimental moisture ascents, and the means of all valid ascents of the two sets of routine stratospheric moisture measurements. In the figure, symbols represent: BRL—Mean of 2 hygrometric ascents by Ballistic Research Laboratories; NRL—Mean of 3 hygrometric ascents by U.S. Naval Research Laboratories; U of D—One hygrometric and one spectroscopic ascent by University of Denver; JMA—Means of the Japanese Meteorological Agency hygro- metric ascents; 100 of which reached or exceeded 300 mb and two of which reached 10 mb; MRF—Means of the British Meteorological Research Flight hygrometric ascents, 400 of which reached or exceeded 300 mb; Vapor Trap—Mean of seven ascents of the United Kingdom Atomic Energy Authority's water vapor absorption device; Molecular Sieve—A single ascent of the General Mills, Inc., water vapor absorption device. The dewpoint profile was constructed by the same procedure. Stratospheric frostpoints were approximated when unavailable from the soundings. Resulting mean annual vertical profiles to 31 km in middle latitudes (35 to 55°N) of mixing ratio and dewpoint-frostpoint, obtained as independent means from the same basic measure- ments of stratospheric moisture and routine tropospheric radio- sonde observations, are presented in the accompanying table. Neither profile can be obtained from the other, since the non- linear relation between mixing ratio and condensation tempera- ture (dewpoint-frostpoint) insures that the means, separately obtained, will differ. From each of the basic profiles, other expressions for the moisture content of the atmosphere have been derived, using Standard Atmosphere conditions where required. The two sets of values for absolute humidity (vapor density), vapor pressure, precipitable water, and relative humidity differ, of course. Preferred values are indicated by asterisk. Relative humidity up to 7 km was computed directly from radiosonde data. The most reliable single element is the mixing ratio, because all the selected data were given in terms of mixing ratio and required no approximations, such as those used for the dewpoint-frost- 670 APPLIED OPTICS / Vol. 1, No. 5 / September 1962
