AIRBORNE MEASUREMENTS OF AEROSOL OPTICAL-PROPERTIES OVER SOUTH-CENTRAL NEW-MEXICO

We used a three wavelength nephelometer (449, 536 and 690 nm) and an aethalometer on board the NOAA King Air research aircraft to assess the contributions of aerosol optical scattering and absorption to shortwave extinction. The measurements were made over south-central New Mexico in February and July 1989. The winter measurements revealed a shallow, polluted planetary boundary layer with cleaner air above. The summer measurements showed a uniformly mixed planetary boundary layer extending from ground level to the operational ceiling of 4.5 km above ground. In both cases the total optical thickness values for the column were similar (0.03) and the fractional contribution of aerosol absorption to the extinction was between 5 and 10%. These results suggest that the aerosol extinction in summer and winter is similar, even though the planetary boundary layer thickness is quite different during the two seasons. They also demonstrate that a suitably instrumented light aircraft can profile the optical properties of the troposphere with high sensitivity and good spatial resolution.