Airborne in-situ Measurements of Radiation, Aerosol Optical Properties and Trace Gases for Evaluation of Remote Sensing Techniques

Satellite remote sensing techniques together with column measurements are increasingly being used for the estimation of tropospheric aerosols and trace gases. As both are often strongly linked to ground sources, the main fraction within a vertical column is likely to exist in the planetary boundary layer. Scattering of light on aerosols in the same altitude range where the substance is expected, makes the estimation of trace gas mixing ratios in the lower troposphere more difficult. Coexistence of trace gases and light scattering aerosols in the planetary boundary layer is, therefore, a challenge for satellite derived trace gas retrieval algorithms, and whether it is possible to compare satellite with ground based remote sensing or airborne in situ measurements depends on the knowledge about the vertical distribution of gases and aerosols. Altitude resolved remote sensing is limited to a few chemical compounds and aerosol properties and not sufficient for a quantitative description of the vertical profiles. For more detailed studies with independent measurement techniques, in situ investigations with airborne platforms are required. A system suitable to be used on small aircraft has been developed for vertical profile measurements. It consists of sensors for actinic UV radiation, aerosol properties and trace gas components and can be flown on a variety of small aircraft reaching altitudes well above the planetary boundary layer (PBL).