Pattern Recognition of Convection in the Atlantic Intertropical Convergence Zone

The Intertropical Convergence Zone (ITCZ) in the Atlantic is typically described as a narrow band of precipitation and deep convection. However, this description often stems from long-term averaging of precipitation or outgoing longwave radiation in the ITCZ. On shorter time scales, the ITCZ is much more dynamic and various classifications of different patterns can be attempted. One possibility is based on satellite images collected during the GATE campaign in 1974 where four patterns - Line, Double Line, Broad and Cluster - were previously identified. In our analysis, we build on the pioneering results from GATE, supplement the category No Clouds, and validate the patterns based on 43 years of harmonized, equal-angle grid geostationary satellite images. In a first attempt, manual classification of these patterns in the visible spectrum proved feasible for 1000 km wide cutouts and for manually defining the extent of the pattern on the entire Atlantic ITCZ. Manual classification for July 2021 has already shown that all classes neither occur with the same frequency nor the same spatial ditribution over all regions of the Atlantic. For further analysis on the appearance of these patterns on longer time scales the satellite images have been classified by a machine learning algorithm, and their frequency dependence on season and region have been analyzed. These results now enable us to ask why these different patterns occur.