towards the operational cloud classification in finland otto hyvärinen cost 722 expert meeting,...
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Towards the operational cloud classification
in Finland
Otto Hyvärinen
COST 722 Expert Meeting, Helsinki, 9 June 2004
Contents• Cloud classification work with NOAA/AVHRR
– in FMI– in Nowcasting SAF (PPS)
• Problems• Future plans
FMI approach to cloud classification with NOAA/AVHRR
• The statistical pattern recognition approach– Collect a lot of training data– Approximate posterior probabilities with neural networks – Use a principled way of handling the uncertainty
• No physics, only data!– Different models for day, night and twilight
• Unfortunately, the development has stalled...
Nowcasting SAF approachwith NOAA/AVHRR
• Developed mostly in SMHI• Traditional thresholding
– Thresholds computed with the help of the radiative transfer models (RTTOV)
• Uncertainty handled more ad hoc
How do they compare?
• Comparison against SYNOP observations of total cloudiness
All stations Stations from "the training area"
Problems?
• Common problems– Twilight!– AVHRR
• FMI problems– no physics should explore RTMs
• Nowcasting SAF problems– bad decision making methods should explore pattern
recognition methods
Towards future
• Is Nowcasting SAF method for AVHRR "good enough" for us?
• From AVHRR to MODIS, VIIRS, etc– how to make this as least painful as possible?– SEVIRI, how useful is it in Finland, really?
• From the satellite cloud classification to the cloud analysis– how to combine remote sensing and in-situ observations with
the model data to real 3D analysis of clouds, fog, and visibility?