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Release of CLAAS-3: The 3rd edition of CM SAF’s SEVIRI-based cloud property data record

The CLAAS-3 record provides cloud properties derived from intercalibrated measurements (Meirink et al., 2013) of the SEVIRI sensor onboard METEOSAT second generation (MSG) satellites. CLAAS-3 is the latest edition of CLAAS with previous editions documented in Stengel et al. (2014) and Benas et al. (2017).

CLAAS-3 includes the following cloud properties: cloud mask/type, cloud top temperature/pressure/height, cloud thermodynamic phase, cloud optical thickness, cloud particle effective radius and cloud water path. Additionally, cloud droplet number concentration and cloud geometrical thickness are provided for liquid clouds. All data are available on multiple processing levels spanning level-2 (native SEVIRI resolution, i.e., 15 minutes repeat cycle and 3 km (nadir) spatial resolution) to level-3 (spatio-temporal aggregations such as daily averages, monthly averages and monthly histograms on a 0.05° x 0.05° grid, as well as monthly mean diurnal cycles and joint cloud optical thickness – cloud top pressure histograms on a 0.25° x 0.25° grid).
CLAAS-3 covers the time period 2004/01 until 2020/12 as climate data record (CDR), but is operationally extended as interim climate data record (ICDR) to the present with a latency of 10 days. Some key features of CLAAS-3 compared to previous editions are:
1) The ICDR contains the same (full) product portfolio as the CDR,
2) Significant improvements for cloud detection with provision of a cloud probability,
3) Significant improvements for vertical placement of clouds (pressure, temperature, height),
4) New cloud effective radius products using the 3.9 µm in addition to the 1.6 µm channel,
5) New cloud droplet number concentration and geometrical thickness products for liquid clouds,
6) Full uncertainty portfolio for all level-2 and level-3 products.

A comprehensive evaluation was conducted and results are summarized in the Validation Report, which composes, along with the Product User Manual and the Algorithm Theoretical Baseline Documents a rich set of CLAAS-3 documentation. With CLAAS-3, regional and large-scale cloud processes at temporal scales of quarter-hours to years can be studied. Furthermore, due to its increasing record length (19 years and growing), CLAAS-3 becomes a suitable source for climate monitoring applications.

The data record can be ordered via the Web User Interface

More information on the data record is available from the DOI page: 10.5676/EUM_SAF_CM/CLAAS/V003


CLAAS-3 Table CLAAS-3 Table Source: CM SAF

Technical specifications
Time period01.01.2004 - present
Temporal resolutionPixel-based products (15 minutes) , daily and monthly mean (DM and MM), monthly mean diurnal cycle (MMDC), monthly histograms (MH)
Spatial coverageMeteosat disk
Spatial resolutionapprox. 4km, native SEVIRI resolution (pixel-based products), 0.05° x 0.05° latitude-longitude grid (DM, MM, MH), 0.25° x 0.25° latitude-longitude grid (MMDC)
Data FormatNetCDF 4, Climate and Forecast (CF) Metadata Convention v1.7


Cloud properties - Product User Manual (PUM)
Cloud properties - Validation Report (VAL)
Cloud properties - Algorithm Theoretical Basis Document (ATBD)

Benas, N., Finkensieper, S., Stengel, M., van Zadelhoff, G.-J., Hanschmann, T., Hollmann, R., and Meirink, J. F.: The MSG-SEVIRI-based cloud property data record CLAAS-2, Earth Syst. Sci. Data, 9, 415-434,, 2017
Meirink, J. F., Roebeling, R. A., and Stammes, P.: Inter-calibration of polar imager solar channels using SEVIRI, Atmos. Meas. Tech., 6, 2495-2508,, 2013
Stengel, M., Kniffka, A., Meirink, J. F., Lockhoff, M., Tan, J., and Hollmann, R.: CLAAS: the CM SAF cloud property data set using SEVIRI, Atmos. Chem. Phys., 14, 4297-4311, doi:10.5194/acp-14-4297-2014, 2014.

NaS / Dec2022

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