BBC Workshop DeBilt, 18.–19. October 2004 Reconstruction of three dimensional cloud fields from two dimensional input datasets Klemens Barfus & Franz H. Berger Technische Universität Dresden Institute of Hydrology and Meteorology Department of Meteorology Tharandt, Germany

BBC Workshop DeBilt, 18.–19. October 2004 Concept DataModificationsReconstruction 1. dataset: cloud parameters from satellite (liquid water path, cloud top height, cloud coverage) 2. dataset: time series of microwave radiometer and cloud radar from inside of satellite observed volume (profiles of liquid water content, cloud base height) Reconstruction of three dimensional cloud fields from two input data sets of cloud parameters Validate the reconstructed cloud field with radiative transfer modelling

BBC Workshop DeBilt, 18.–19. October 2004 DataModificationsReconstruction Concept Example of input data Combined data from September, 23, 2001 area ~ 400 x 400 km 2 test areas

Problems BBC Workshop DeBilt, 18.–19. October 2004 DataModificationsReconstruction Concept measured three dimensional cloud fields does not exist ⇨ for the development of method modeled data are needed data of Lokalmodell of the German Weather Service with a spatial resolution of 1 km and storage of subgrid cloud water are used ⇨ problem: liquid water is to low – modified with liquid water from satellite ⇨ problem: subgrid cloud structure is not known

BBC Workshop DeBilt, 18.–19. October 2004 DataModificationsReconstruction Concept Liquid Water Path data from different sources Comparison of spatial averages of LWP data for Cabauw

BBC Workshop DeBilt, 18.–19. October 2004 Scaling up liquid water path from satellite with liquid water path from microwave radiometer Scaling up liquid water path from LM with scaled liquid water path from satellite (with conservation of lwc/lwp ratios of the different levels) Erase liquid water path in columns, where satellite indicates cloud free conditions Replace columns indicated as cloudy by satellite but in LM cloudfree with best fitting column from the neighbourhood DataModificationsReconstruction Concept Modifications of LM data

BBC Workshop DeBilt, 18.–19. October 2004 DataModificationsReconstruction Concept Reconstruction of three dimensional cloud field multiple linear regression from cloud top height and LWP cloud base height from nearest cloud base (first steps of reconstruction:) approximation of cloud base height from nearest cloud base in vertical slice

BBC Workshop DeBilt, 18.–19. October 2004 DataModificationsReconstruction Concept distribution of cloud water according to lwc profile of best fitting cloud concerning cloud thickness from the vertical slice other lwc profiles ? problem: subgrid cloud structure has to be defined which cloud mask ? problem: parametrisation of effective radius ⇨ parametrisation from Bower et al. (1994) other parametrisations of effective radius ? Reconstruction: open questions

BBC Workshop DeBilt, 18.–19. October 2004 DataModificationsReconstruction Concept Cloudmasks Which more realistic assumptions about cloud field structure can be applied ? Assumptions of cloud field structure with very simple cloud masks

BBC Workshop DeBilt, 18.–19. October 2004 DataModificationsReconstruction Concept Cloudfields Reconstructed cloudfields

BBC Workshop DeBilt, 18.–19. October 2004 DataModificationsReconstruction Simulation Radiative transfer modelling SHDOM cannot simulate the whole area at once - area has to be subdivided into individually simulated areas

BBC Workshop DeBilt, 18.–19. October 2004 NextModificationsReconstruction Simulation next other parametrisations of cloud field differences in radiation field from different cloud field realizations use mc-unik (Monte Carlo Code from Uni Kiel) use surrogate cloud fields from Victor