Stratospheric aerosol measurements with implications for global climate.

In this paper we present measurement results obtained in New Mexico with bistatic optical probing of the atmosphere using a searchlight beam. The data yield vertical profiles of the aerosol attenuation coefficient. Because they approximate proportionality to aerosol concentration, these profiles provide information concerning the aerosol layer structure and its parameters. During a 9-day period in October and November 1970, a series of forty-one such profiles was obtained which includes altitudes 12-25 km, selected for study because of the relatively high aerosol content of this stratospheric region and its relation to global climate. The mean stratospheric aerosol distribution for this period is double layered with maxima at 15.6 km and 19.3 km. An early phase of volcanic dust incursion is examined. A chronology of stratospheric aerosol concentration levels is developed based on measurements with the same instrumentation at the same sites since February 1963. The chronology shows that the particulate background level of a nonvolcanic, nonpolluted stratosphere is represented by an aerosol optical thickness Tau(p)(O.55 micro) = 2.0 x 10(-2). A calculation with this background level is included, which indicates feasibility of a laser-satellite method for acquiring data related to global climate. The Appendix introduces an original method of numerical integration (used in the calculations), which is suited to radiative transfer studies.