Characterization of the diurnal cycle of maximum rainfall in tropical cyclones

We analyze the diurnal cycle of maximum rainfall from similar to 300 TCs from March 2014 through February 2017, by cross-referencing the path of tropical cyclones (TCs) and high-resolution rainfall estimates from IMERG (Integrated Multi-satellitE Rainfall from GPM - Global Precipitation Measurement mission). IMERG is a gridded satellite product that offers high-resolution rainfall estimates at a spatiotemporal resolution of 0.1 degrees x 0.1 degrees every 30 min, which are particularly suitable for these analyses. Because of the nature of the data, we use circular statistics. Circular statistics allows us to account for the natural periodicity of a random variable such as the time of the day at which maximum rainfall from TCs occurs. We follow the non-parametric approach of Mixtures of Von Mises-Fisher distribution (MvMF), which enables an easy-to-interpret parameter identification of multimodal and anisotropic distributions of the TC-rainfall. We stratify our analysis by storm duration, maturity, and intensity, basin of origin, radial proximity to the center of the storm, and whether the storm is over the ocean or land. In general, and across all scales, we find that there are mainly two cycles of maximum TC-rainfall: one diurnal cycle with peaks at similar to 10 and similar to 22 h (local time), and one semi-diurnal cycle with peaks at similar to 2 and similar to 5 h (local time). Although in a smaller proportion, the latter exhibits a weak afternoon alternative, i.e., similar to 14 and similar to 18 h (local time).