Climatology of Rainfall Distribution and Asymmetries of Tropical Cyclones: A Global Perspective

Abstract

Estimating the magnitude of tropical cyclone (TC) rainfall at different landfalling states is an important aspect of the TC forecast that directly affects the level of response from emergency managers in coastal areas. This research analyses the spatial distribution of the rainfall magnitude in tropical cyclones (TCs) at different stages over global oceans. The research’s central hypothesis is that TC rainfall exhibits distinct features in the long-term satellite dataset due to the evolution of the spatial distribution, radial variation, and asymmetries at the stages before, during, and after landfall. The resulting patterns are analyzed through a statistical approach that takes advantage of a 20-year global satellite database of rainfall retrievals from the TRMM/GPM constellation, with the aim to achieve two main objectives: 1) The first objective was to explore the global trends of TC rainfall rates using observational evidence provided by a satellite-based climatology. Results indicate there is an increasing trend in the global average TC rainfall rate of about 1.3% per year, with a more pronounced trend in the northern hemisphere than in the southern hemisphere. 2) The second objective was to examine the spatial distribution of the magnitude and axisymmetric intensity profiles of rainfall over the six TC-prone basins. The obtained differences were quantitatively investigated in terms of geographic location, sub-regions within the storm, and TC intensities. Results indicate that major hurricanes in the Atlantic basin exhibit heavier inner-core rainfall rates than those in any other basins, and this difference is highly correlated to specific environmental conditions. Overall, with the achievement of the above-described objectives, this document identifies and summarizes the dominant factors that control rainfall distribution in global TCs, mainly focused on the differences during landfilling processes

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