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Project Description

The three dimensional structure of cloud poses a number of scientific problems. In the first place the possible anomalous absorption in clouds may be due to cloud structure. Furthermore, the cloud structure will alter the relation between albedo and optical depth. Thirdly, the relation between dynamical exchange processes and 4D structure is not well understood. These are the three main scientific question 4D-CLOUDS want to contribute to.

Within the 4D-CLOUDS project, the university of Bonn will focus on:

  • the combination of the microwave radiometer (MICCY) brightness temperatures with MIRACLE radar reflectivity profile to determine profiles of liquid water content (LWC),

  • the remote sensing measurements of the three dimensional cloud structures by scanning,

  • Develop algorithms to convert the measured cloud properties into synthetic cloud fields for radiative transfer modelling,

  • the separation of cloud and rain liquid water content and

  • dynamical modelling of boundary layer clouds.

The three dimensional cloud structures will be measured by combining scanning measurements with a cloud radar (MIRACLE of GKSS) and the MICCY microwave radiometer. MICCY measures the atmospheric emission at 22 frequencies in the microwave region (20-90 GHz). The signal contains contributions from the water vapour, oxygen and cloud liquid water. The polarisation information contained in the measurement may be used to distinguish between cloud and rain liquid water by scattering effects of oblate precipitation particles. These measurement with high temporal and angular resolution (1 sec and 1 degree) will also be analysed to investigate scaling properties of the LWC in co-operation with Heidelberg.

New algorithms, parameterisations for radiative transfer will be implemented in the non-hydrostatic Lokal Model in the modelling component of the project. With this enhanced model the influence of the three dimensional clouds on the exchange processes of sensible and latent heat in the boundary layer will be investigated.

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Meteorological Institute
University of Bonn
Auf dem Hügel 20
53121 Bonn, Germany

Sekretariat: Pia Rosen, Tel.: +49 (0)228 73-5190, Fax: +49 (0)228 73-5188, e-mail: