AEROSOL-SIZE DISTRIBUTIONS OBTAINED FROM HALOE SPECTRAL EXTINCTION MEASUREMENTS

A technique was developed to use multiwavelength aerosol extinction me asurements from the Halogen Occultation Experiment (HALOE) to determin e the size distribution of stratospheric H2O-H2SO4 aerosols. Although the HALOE extinction spectrum alone cannot be used to reliably infer t he aerosol size distribution (except when the aerosol population conta ins particles larger than about 0.5 mu m), the inverse problem becomes highly defined when the effective radius is known. Using theoretical relationships derived from in situ aerosol measurements. we found that the effective radius can be determined from the HALOE 2.45 mu m extin ction with uncertainties of about +/-15%. Using extinction ratios with the effective radii determined from the HALOE extinctions, we obtaine d unimodal lognormal size distributions. The HALOE size distributions are generally unbiased with respect to coincident in situ aerosol meas urements. Error analysis reveals that uncertainties in the inferred su rface areas and volumes are less than 30% and 15%, respectively. Infer ring size distributions from the HALOE data set provides global and te mporal aerosol information, which can satisfy important needs for inve stigations of the Earth's radiative and chemical balance.