Optical depths and haze particle sizes during AGASP III

The optical properties of Arctic Haze were studied using a total-direct-diffuse radiometer as part of the Arctic Gas Aerosol Sampling Project, part III (AGASP III). The radiometer was installed on the NOAA WP-3D research aircraft and measured solar downwelling irradiance in seven narrow-band channels in the visible and near-infra-red. Haze optical depths had maximum values near 0.1 in the mid-visible for AGASP flights 310 and 311. An inferred particle size spectrum from flight 311 extinction measurements showed two dominant modes near 0.1 and 0.8 μm. A method of retrieving the angular dependence of scattered radiation is presented and suggests the presence of thin cirrus.