This project has two main objectives: a systematic experimental investigation of the impact of the 3D cloud structure on the atmospheric radiation field and the validation of parameters derived from ENVISAT and MSG data with special emphasis on the impact of the 3D cloud structure.
The following instruments are installed on an airborne research platform, a Cessna 207 T: The compact airborne spectrographic imager casi (spectral range: 450-950 nm) allows the investigation of the spatial structure of clouds, and a Fourier spectrometer FTIR measures radiances in the infra-red spectral range (5-17 mm). The imaging spectrographic system (FUBISS) will be extended to combine radiance (different viewing angles) and irradiance measurements to observe the inhomogeneity of the radiation field due to clouds at fixed observation points (spectral range: 400-1000 nm). Spectral high resolution (spectral range: 600-1000 nm) and near infra-red (950-1700 nm) measurements at nadir are the basis of further investigations. Flight levels below, within, and above clouds will be performed.
The measured radiances will be compared with 1D radiative transport simulations. A systematic analysis of the differences between modelled and measured radiation fields will be carried out and quantified for different cloud fractions and cloud properties. This will be the basis for 3D radiative transport parameterisations and for the derivation of characteristic scales.
Algorithms, which allow the derivation of microphysical parameters, the cloud top pressure, and the optical thickness (level 2 parameters), will be applied on the received data set. To a certain degree a validation is possible by experiments made by other partners (e.g., GKSS).
Through the combination of the characterisation of the inhomogeneity of the 3D clouds and the derived level 2 cloud parameters as derived from MERIS and MSG-SEVIRI measurements the second objective will be approached. If the satellite starts of ENVISAT and MSG, will not be in time, the data of operating satellites, e.g. METEOSAT or TERRA-MODIS, will be used.
Institute for Space Sciences
Dept. of Geosciences
Free University of Berlin
12165 Berlin, Germany