The relationship between precipitation and its spatial organisation in the trades observed during EUREC4A

Trade wind convection organises into a rich spectrum of spatial patterns, often in conjunction with precipitation development. This raises the question of the role of spatial organisation for precipitation and vice versa. We analyse scenes of trade wind convection scanned by the C-band radar Poldirad during the EUREC4A field campaign to investigate how trade wind precipitation fields are spatially organised, quantified by the cells' number, mean size and spatial arrangement, and how this matters for precipitation characteristics. During EUREC4A, a mean rain cell size of about 5 km and a mean distance to the nearest neighbouring cell of about 14 km were most common. We find that the amount of precipitation in a scene is influenced in a different way than the intensity of precipitation by the spatial organization. While precipitation amount increases with mean cell size and number, as it scales well with precipitation fraction, precipitation intensity increases predominantly with mean cell size. The increase of precipitation intensity with mean cell size, however, differs with the moisture regime. It is stronger in dry than in moist scenes. Dry scenes typically contain fewer cells with a higher degree of clustering than moist scenes. The highest precipitation intensities hence typically occur in scenes with on average large and few cells and a high degree of clustering, while the highest precipitation amounts typically occur in scenes with on average large and numerous cells and a low degree of clustering. Our analyses suggest that the cells' spatial arrangement is important for precipitation formation in dry environments, but mainly weakly correlated with precipitation characteristics and thus of second order importance across all regimes. Our analyses highlight the importance of cell size, as it influences both the intensity and amount of precipitation.