A mid-latitude ozone model for the 1976 U.S. Standard Atmosphere

Abstract

A mid-latitude northern hemisphere model of the daytime ozone distribution in the troposphere, stratosphere, and lower mesosphere has been constructed. Data from rocket soundings in the latitude range of 45øN q- 15øN, results of balloon soundings at latitudes from 41 ø to 47øN, and latitude gradients from satellite ozone observations have been combined to produce estimates of the annual mean ozone concentration and its variability at heights up to 74 km for an effective latitude of 45øN. This model is a revision for heights above 26 km of the tentative mid-latitude ozone model, included in the U.S. Standard Atmosphere Supplements, 1966, and has been adopted for use in the U.S. Standard Atmosphere, 1976. Interest in atmospheric ozone has been increasing due to predictions of ozone depletion from stratospheric pollutants. At the present time the only widely accepted reference ozone profile available for design studies and theoretical modeling of the stratosphere was published in the U.S. Standardltmo- sphere Supplements, 1966 (Committee on Extension to the Standard/ltmosphere (COES/I), 1967) . That model of the mean annual vertical ozone distribution at 45øN was based on approximately 150 balloon ozonesonde flights at heights from 2 to 34 km and on two rocket soundings and theoretical calculations above 34 km. Since 1965 about 150 rocket sound- ings of ozone have been made at many geographic locations, and several developmental ozone sensors have been carried on satellites. The purpose of this paper is to present an improve- ment to the upper portion of the 1966 model by the use of a selected set of new soundings. The details of the selection process are described in a background document (Krueger and Minzner, unpublished manuscript, 1976). The resulting empir- ical model of the mean annual ozone profile at 45øN also contains an initial estimation of the time and space variability above balloon altitudes at that latitude. For heights below 27 km the ozone model described herein is essentially unchanged from that of the 1966 supple- ments. The data determining this portion of the model were originally obtained from a systematic program of weekly bal- loon ozonesonde ascents made throughout 1963 (Hering and Borden, 1964). For heights above 27 km the ozone model was computed from a set of column densities of ozone, a quantity usually obtained from optical observations and frequently ex- 'pressed in units of centimeters of ozone at standard temper- ature and pressure (STP) per unit vertical distance (atm- cm/km). The column densities of this model for heights above 32 km were determined from 12 daytime and five twilight rocket measurements of the ozone distribution (15 over North America and two over Japan), while the values for the height region from 28 to 32 km represent a composite of both rocket and balloon data. Latitude gradients for correction of the mean rocket data have been derived from ozone measurements with the backscatter ultraviolet (BUV) system on Nimbus 4 (Heath et al., 1973). These satellite data have not been used directly in the model because of height resolution consid- erations. However, such data will be very valuable for the extension of this model to other latitudes and the establishment