Extended Abstract (96K)P2.2
Tracking cloud patterns by rapid scan imagery in the Alpine region
Martin Bolliger, MeteoSwiss, Zurich, Switzerland; and P. Binder and A. Rossa
Convective and stratiform cloud patterns are investigated by means of Meteosat-6 rapid scan imagery recorded over the Lago Maggiore target area during the MAP SOP. The data of the infrared channel are used to implement an automatic cloud tracking algorithm by a pattern-oriented technique. Tracking in the Alpine area is challenging due to the complex processes related to topography. In this case tracking is not used for the derivation of cloud motion winds, but rather to extract development within the tracked cloud fields.
The increase of temporal resolution from the operational 30 minutes interval to the rapid scanning 5 minutes interval allows continuous cloud tracking and helps to isolate information on cloud development. The high temporal resolution favours the tracking of cloud patterns, being rapidly developing convective systems or weakly textured stratiform clouds. The latter can hardly be followed on a contigous path by 30 minutes timesteps. Apart from the temporal resolution, the ability to track a cloud pattern is dependent on the intensity of cloud development and on the texture of the tracked pattern. Investigations reveal, that the tracking accuracy of a weakly textured cloud pattern with weak cloud development (i.e. stratiform cloud pattern) depends crucially on the high temporal resolution of the imagery, more than in the case of distinct cloud patterns like convective cells with moderate development. Further elements of sensitivity apart from the temporal resolution are the size of the target window and the search area. These sensitivities will be illustrated and inferences drawn for the predictability of cloud patterns.
Poster Session 2, Orographic Precipitation/Operational and Numerical Weather Prediction (with Coffee Break)
Wednesday, 19 June 2002, 9:15 AM-11:00 AM
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