Surface-, water vapor-, and cloud products from polar orbiting satellites

In this work package we perform continuous updates concerning the system set-up of the data server at the Freie Universität Berlin, which was initially build up in phase 1. Due to its direct linkage to the data servers in Cologne and Hamburg, this is done in close cooperation with project members from respective institutions. In addition, existing full-domain multi-annual data sets of MODIS surface products will be extended both in space and time. Also, new data sets from MODIS cloud and integrated water vapor products will be created. Moreover, at the supersites, time series of above mentioned data sets are being created  to allow for straightforward comparisons between ground-based observations, satellite-based observations, and model simulations. As for the existing data sets, the new data sets are being created in the standardized format as defined within the project and stored in the local database.

Ground based networks

Germany features dense networks of GPS observations to retrieve the integrated vapour content and of ceilometers to observe cloud base. For the latter in case backscatter profiles are available it is also possible to derive boundary layer height .The data transfer from the network providers (GFZ Potsdam for GPS and DWD for Ceilometer) to the data archive will be continued. As added value product, we will additional generate a combined product of Ceilometer derived cloud base height and cloud top height from MSG observations. The quality control of the GPS will be improved in close cooperation with GFZ Potsdam. Together with DWD it will be explored whether backscatter profiles might be used for long-term boundary layer characterization.

Precipitation from radar networks

Radar reflectivities and radar rain rates for Germany and Barbados are provided within the framework of task 4. These data sets are specially important for S5, which uses radar information to study convective organizations in both areas and to investigate whether there is a difference in the macroscopic structure of these organizations between Europe and the Caribbean. For Germany non-polarimetric 2D radar reflectivities and rain rates composites (RADOLAN from DWD) were provided since 2007 and are continuously updated. This data has resolution of 1 km and 5 minutes.

Polarimetric 3D composites will also be provided for Germany. Since polarimetric radars are able, for example, to distinguish between hydrometeors in different phases (solid, liquid), there is a lower sensitivity to the drop size distribution and information about the average particle size can be taken into account, there is an improvement in the estimation of the rain rates. These composites will certainly not only improve the study of convective organizations in S5, but they will also be usefull for the scientific community in generall.

For Barbados there is one S-band Doppler radar available. The radar reflectivity is already provided from November 2008 to November 2016 (not continuously). The temporal resolution might vary from one data set to another (5-, 10-, 15-minutes).

METEOSAT products over Germany and the tropical Atlantic

Besides, a high-resolution data set of Meteosat-based cloud properties will be processed and made available for model validation purposes. The cloud properties include cloud top height, effective radius, optical thickness and water path. An example is shown in the Figure 1 where simulated liquid cloud water path has been compared to Meteosat-based liquid water path retrievals. The Figure has been taken from one of our latest journal articles (Bley, S., H. Deneke, F. Senf, and L. Scheck (2017), Metrics for the evaluation of warm convective cloud fields in a large-eddy simulation with Meteosat images, Quart. J. Roy. Meteor. Soc., 143(705), 2050–2060, doi:10.1002/qj.3067.) in which we could further show that simulated ICON-LEM liquid cloud characteristics are consistent with their observed counterparts with regard to cloud size distributions and the decorrelation behavior of time and space scales.

The imaging radiometers aboard the geostationary Meteosat platforms are the ideal instruments to characterize convective development and structure of convective cloud fields due to their frequent temporal update rate and high spatial resolution. We use satellite data that are available with a frequency of 5 minutes allowing for the study of temporal changes within the moving cloud frame (see Figure below; taken from: Bley, S., Deneke, H. and Senf, F. (2016): Meteosat-Based Characterization of the Spatio-Temporal Evolution of Warm Convective Cloud Fields over Central Europe, J. Appl. Meteor. Climatol., 55, 2181-2195,  doi: 10.1175/JAMC-D-15-0335.1).

HALO aircraft data

The NARVAL (Next generation Aircraft Remote Sensing for Validation Studies) mission of the new research aircraft HALO took place in winter 2013/14 with about 130 flight hours over the North Atlantic. HALO was equipped with a comprehensive suite of remote sensing instrument comprising e.g. a cloud radar, microwave radiometers and a lidar to observe vertical cloud profiles in detail. Data of the first part of the NARVAL campaign was obtained in the Barbados region and is of great interest for studies in the tropical domain, whereas the second part was focused on the post-frontal convection in extratropical cyclones, which is valuable for the S6 storm track project.

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