Automatic Tracking and Characterization of African Convective Systems on Meteosat Pictures

Yves Arnaud Laboratoire d'Hydrologie de l'ORSTOM, Montpellier, France

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Michel Desbois Laboratoire de Météorologie Dynamique du CNRS, Palaiseau, France

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Joel Maizi Informatique ORSTOM, Montpellier, France

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Abstract

With the objective of budding climatological statistics on propagating African convective systems and extracting pertinent parameters for the evaluation of precipitation an automatic method of tracking clouds with cold tops on Meteosat infrared (IR) images is established. This method takes into account eventual separation or merging of clouds. Results obtained in several cases not only demonstrate the capability of the method to perform correct tracking in different situations, but also show that objective determination of parameters, such as propagation speeds, system area, and volume index, is possible. The analysis of the time evolution of these last parameters allows a clear characterization of the cloud life cycle with its growing and decreasing stages, which may be useful for improving precipitation-estimation methods based only on cold-cloud occurrences or cloud-top temperatures.

Abstract

With the objective of budding climatological statistics on propagating African convective systems and extracting pertinent parameters for the evaluation of precipitation an automatic method of tracking clouds with cold tops on Meteosat infrared (IR) images is established. This method takes into account eventual separation or merging of clouds. Results obtained in several cases not only demonstrate the capability of the method to perform correct tracking in different situations, but also show that objective determination of parameters, such as propagation speeds, system area, and volume index, is possible. The analysis of the time evolution of these last parameters allows a clear characterization of the cloud life cycle with its growing and decreasing stages, which may be useful for improving precipitation-estimation methods based only on cold-cloud occurrences or cloud-top temperatures.

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