Understanding the Spatial Organization of Precipitation Extremes

Thursday, December 13, 2018 - 11:50
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We introduce the idea of simultaneous heavy precipitation events (SHPEs) to understand whether extreme precipitation has a spatial organization that is manifest as specified tracks or contiguous fields with inherent scaling relationships. For this purpose, we created a database of SHPEs from 1242 Global Historical Climatology Network rainfall stations across the contiguous United States. The SHPEs are investigated for spatial orientation, areal extents and recurrence. Various unsupervised learning techniques and spatial summary metrics applied on the SHPEs reveal that there are distinct spatial characteristics in April-May-June (AMJ) and September-October-November (SON) seasons. These spatial characteristics are in turn related to large-scale earth system controls and land-atmosphere interactions. The preliminary results indicate that the nocturnal and cyclone induced low-level jets are primarily controlling the spatial manifestation in AMJ and the severe tropical cyclones are defining the spatial features of the SON SHPEs across the Midwest and Southern United States. The results are also corroborated with a supplemental CMAP gridded rainfall data. Understanding the spatial patterns of SHPEs and their associated large-scale ocean-atmospheric circulation features can help us in better projecting the flooding risk at multi space and time scales.

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