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Abstract

Over convergence zones, persistent organized convective cloud systems can extend from the tropics to the extratropics and can form synoptic cloud bands. An example is the Pacific convergence zone, which can affect precipitation on the Polynesian islands. These cloud bands are the combination of tropical intrusions of extratropical Rossby waves and of processes deeply rooted in the tropics, such as eastward propagating equatorial waves or equatorial Rossby-waves forced by convection over the Maritime Continent. Here we present a new atmospheric cloud band detection method based on outgoing longwave radiation using computer vision techniques, with the capability to detect long cloud bands from different gridded datasets and variables. It handles merging and splitting of cloud bands, which allows for an understanding of the life cycle of each cloud band as well as of their climatology and of associated precipitation. The aim of this study is to detect cloud bands in order to better understand the different tropical-extratropical connections and to evaluate the differences in cloud band types between basins.