Browsing by Author "Alshehri, Mohammed Saleh"

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Large-Scale Meteorological Patterns as Drivers of Mixed Populations in Precipitation and Flood Extremes across the Conterminous United States
(Saudi Digital Library, 2025) Alshehri, Mohammed Saleh; Vivoni, Enrique R
Traditional precipitation and flood frequency analyses assume homogeneous statistical populations, potentially obscuring hydrometeorological variability driven by distinct atmospheric mechanisms. This dissertation quantifies how large-scale meteorological patterns (LSMPs) control precipitation and flood generation across the conterminous United States. Using 2,861 precipitation gauges (1980–2018) and 585 minimally disturbed watersheds (1980–2014), the study addresses: (1) where and when different LSMPs dominate precipitation and streamflow generation, (2) whether LSMP-driven events form statistically distinct populations, and (3) whether LSMP frequencies have exhibited temporal trends. First, fronts (FRTs) dominate non-zero precipitation nationwide (45–75%), with extratropical cyclones (ETCs) contributing 12–33%. Atmospheric rivers (ARs) generate 50–65% of extremes along the Pacific coast, while tropical cyclones (TCs) produce 10–18% in the southeast. ARs deliver up to 84% of flood peaks in the Pacific domain, with TCs influencing 54% of southeast and Gulf Coast watersheds. Second, statistical testing examined whether LSMPs produce distinct distribu- tions. For non-zero precipitation, two-sample tests rejected the null hypothesis at 80% of gauges. For annual peak flows, 31% of watersheds exhibited distinct pop- ulations between primary and secondary LSMPs, concentrated along coastal mar- gins: AR–ETC (100% separation), AR–FRONT (79% along the Pacific Coast), and FRONT–TC (100% in the southeast and Gulf Coast). In contrast, 63% of watersheds showed no distinction, predominantly in continental interiors where ETC–FRONT combinations differed in only 18% of cases. Third, FRT frequency increased in the northeast while declining in the southwest; TC occurrence rose across the central plains; AR frequency showed modest Pacific-coast declines. Overall, this dissertation supports developing mixed-population frameworks for frequency analysis that explicitly account for LSMPs. Recognition of LSMPs and their characteristic hydrologic signatures may facilitate more robust policies for water resources management.
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