NWCSAF: Meteosat IR10.8 with ASII overlay

Up till this point the products of the NWC SAF thus seen only identified and characterised the areas in the cloudfree regions. Two products that identify and characterise clouds are ASII and ASII-NWP. Where ASII stands for Automatic Satellite Image Interpretation.

The basic concept of ASII is the identification of:

• Detection of frontal areas
• Detection of S-shaped lines
• Detection of circular-shaped cells
• Detection of narrow cloud fibres
• Detection of black stripes in WV images
• Detection of spiral cloud structures

A segmentation divides the IR and WV satellite images into sub-regions being coherent in terms of brightness and texture. The classification process assignes qualities of different conceptual models to these coherent areas. At 06UTC the convection over Austria, Czech Republic and Poland has not started but concentrating on the frontal system on which the convection starts some interesting thing can be identified. The front is marked by c, • , w, m and ~ . Where

• c stands for Cold Front
• • for the embedded convective cells in the Cold Front
• w denotes the Warm Front cloudiness
• m indicate convective cells, where the yellow colour represents the mature cells, a magenta colour for the developing cells and blue colour for decaying cells.
• ~ is the sign for a developing wave on the cyclonic side of the frontal band.

In the next few hours one can see the wave like structure moving northwards along the frontal band. A new wave is recognised over northern France around 0830UTC. North of the Pyrenees ASII recognises l indicating the embedded lee clouds. Also interesting is the patch of cloudiness over the North Sea which is identified as co, or Comma. The cloudiness that developes in a thickness trough under CA is about to merge with the frontal band into an Instant Occlusion. As the time evolves also more “m” are recognised in different colours. An indication of the increase in convection.

Around 11UTC the convection ahead of the front is about to start. North of the Alps the first cells just emerged and are positively identified as Cbs. The magenta colour again indicates that these cells are still developing and should be looked at in following timesteps.