Cloud Products

The basic motivation for retrieving cloud climate products from satellite data is that clouds play an important role in the global energy and water cycle. In particular, the presence of clouds dominates the planetary albedo which is a crucial quantity that controls the fraction of the incoming solar radiation that is directly reflected back to space. Consequently, a very important task for climate monitoring missions is to document any changes in the planetary albedo associated with changes in global cloudiness. Important is also to study associated potential feedback links to changes in atmospheric temperatures and water vapour contents.

Cloud fraction from CLARA-A2 (1982-2015)

Furthermore, the fact that different types of clouds have different reflection and absorption characteristics motivates the definition of an additional set of cloud physical properties (such as cloud optical thickness and cloud liquid water path and cloud phase products) as a complement to the traditional cloud amount, cloud type and cloud top products.

The CM SAF cloud products are mainly derived from passive imaging sensors carried by operational polar and geostationary weather satellites. For the polar satellites the main instrument is the Advanced Very High Resolution Radiometer (AVHRR) operated onboard the polar National Oceanic and Atmospheric Administration (NOAA) satellites and onboard the EUMETSAT MetOp satellites. For geostationary satellites CM SAF cloud products are currently made exclusively based on the EUMETSAT METEOSAT satellites covering the European and Atlantic region. Before 2004 products are based on data from the METEOSAT Visible and Infrared (MVIRI) sensor while since 2004 these products are also complemented by products from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) sensor with 12 spectral bands.

Polar CM SAF cloud products will be extended and complemented in the future by products from the high resolution infrared vertical sounder (HIRS) and products from the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor replacing AVHRR on upcoming polar satellites. Geostationary cloud products from more satellites than METEOSAT will also be considered in the future.

Further details on the products in general, on retrieval details and physical basis as well as on quality can be found in the Product User Manuals (PUM), the Algorithm Theoretical Basis Documents (ATBD), and the Validation Reports (ValRep). The products can be ordered via the Web User Interface. Some more details about the processing scheme used to calculate our products are given in Kaspar et al. (2009).

The CM SAF cloud products, i.e., thematic cloud climate data records (CDRs) and interim cloud climate data records (ICDRs), are useful for evaluating cloud simulations from current atmospheric forecasting models as well as from climate models, e.g., as demonstrated by Zhang et al. (2005). An important aspect here is that tools (referred to as satellite dataset simulators, see Bodas-Salcedo et al., 2011) are developed by CM SAF to assist in the inter-comparison of satellite observations and climate model data.

References:

• Bodas-Salcedo, A., M. J. Webb, S. Bony, H. Chepfer, J.-L. Dufresne, S. A. Klein, Y. Zhang, R. Marchand, J. M. Haynes, R. Pincus, and V. O. John (2011), COSP: Satellite simulation software for model assessment, Bull. Am. Meteorol. Soc., 1023-1043, doi:10.1175/2011BAMS2856.1.
• Kaspar, F., R. Hollmann, M. Lockhoff, K.-G. Karlsson, A. Dybbroe, P. Fuchs, N. Selbach, D. Stein, J. Schulz, 2009: Operational generation of AVHRR-based cloud products for Europe and the Arctic at EUMETSAT’s Satellite Application Facility on Climate Monitoring (CM SAF), Adv. Sci. Res., 3, 45-51.
• Karlsson, K.-G., U. Willén, C. Jones and K. Wyser, 2008: Evaluation of regional cloud climate simulations over Scandinavia using a 10-year NOAA Advanced Very High Resolution Radiometer cloud climatology, J. Geophys. Res., 113, D01203, doi:10.1029/2007JD008658.
• Zhang, M.H., et al., 2005: Comparing clouds and their seasonal variations in 10 atmospheric general circulation models with satellite measurements, J. Geophys. Res., 110, D15S02, doi:10.1029/2004JD005021.R.

K-G K / Feb2022