Atmospheric Radiation Group

In cooperation with the Alfred Wegener Institute for Polar and Marine Research (AWI), we investigate Arctic boundary layer clouds, mostly stratiform clouds, by airborne remote sensing. The focus of our research is the impact of ice crystals (occurrence, horizontal and vertical distribution) on the radiative transfer within these clouds. The measurements have been conducted on board of the Polar 2 and Polar 5 aircraft during several international experiments. The most recent one was VERDI in 2012. For spring of 2014, we are planning the follow-up campaign RACEPAC.

The investigation of the radiative properties of midlatitude cirrus will be one aim of the HALO mission ML-Cirrus for which we will perform airborne measurements of spectral irradiance and radiance. The combination of both quantities allows us to validate the conversion of radiance into irradiance as commonly done during the analysis of satellite data.
Furthermore, we plan to operate the measurement system AIRTOSS to probe cirrus clouds simultaneously by remote sensing and in situ measurements. Ground-based measurements during the CARRIBA campaign at Barbados using the hyperspectral imaging sensor AisaEagle were used to derive the radiative properties of tropical cirrus clouds.

A new measurements platform, SMART-HELIOS, has been developed to simultaneously investigate trade wind cumuli by remote sensing and in situ measurements of cloud properties. The measurements will primarily be used to investigate the three-dimensional radiative transfer in such clouds and to validate the satellite-based retrievals of their properties.
Deep convective clouds will be investigated by airborne radiation measurements during the HALO mission ACRIDICON and are under investigation through ground-based measurements combining passive (solar radiation) and active (lidar) techniques.
Our group coordinated the ground-based ACRIDICON-Zugspitze campaign in 2012 that focused on aerosols, clouds, radiation and cloud dynamics and their interaction.

Within the DFG Research Group SAMUM we investigated the radiative forcing of Saharan dust based on observations during the field campaigns SAMUM I and SAMUM II. Airborne and ground-based radiation measurements were conducted to analyse the radiative transfer in dependence of aerosol and surface properties.

As one part of the DFG priority program 1233 Megacities we investigated remote-sensing methods of aerosol optical properties in urban areas. Airborne and ground-based radiation measurements were used to verify those methods. Among other parameters, the airborne measurements provided a detailed characterization of the surface reflectivity which was used to improve current satellite retrieval algorithms for these urban areas.