Browsing by Subject "Climatology"
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Item Convective weather hazards in the Twin Cities Metropolitan Area, MN(2008-12) Blumenfeld, Kenneth A.This dissertation investigates the frequency and intensity of severe convective storms, and their associated hazards, in the Twin Cities Metropolitan Area (TCMA), Minnesota. Using public severe weather reports databases and high spatial density rain gauge data, annual frequencies and return-periods are calculated for tornadoes, damaging winds, large hail, and flood-inducing rainfall. The hypothesis that severe thunderstorms and tornadoes are less likely in the central TCMA than in surrounding areas also is examined, and techniques for estimating 100-year rainfall amounts are developed and discussed. This research finds that: i) storms capable of significant damage somewhere within the TCMA recur annually (sometimes multiple times per year), while storms virtually certain to cause such damage recur every 2-3 years; ii) though severe weather reports data are not amenable to classical comparative statistical testing, careful treatment of them suggests all types and intensity categories of severe convective weather have been and should continue to be approximately as common in the central TCMA as in surrounding areas; and iii) applications of Generalized Extreme Value (GEV) statistics and areal analyses of rainfall data lead to significantly larger (25-50%) estimates of 100-year rainfall amounts in the TCMA and parts of Minnesota than those currently published and used for precipitation design. The growth of the TCMA, the popular sentiment that downtown areas somehow deter severe storms and tornadoes, and the prior underestimation of extreme rainfall thresholds for precipitation design, all act to enhance local susceptibility to hazards from severe convective storms.Item Gonzalez 2021 tagged CO model archive(2021-04-19) Millet, Dylan B.; Gonzalez, Andres; Yu, Xueying; dbm@umn.edu; Millet, Dylan B.; University of Minnesota Atmospheric Chemistry GroupThis archive contains model code, input files, and simulation results for atmospheric carbon monoxide (CO) posted in association with the referenced paper.Item Intensity of Extreme Rainfall Events Over Minnesota(Minnesota Department of Transportation, 1998-11) Skaggs, Richard H.This study looks at precipitation design values, among the most important and widely used pieces of climatological information. Researchers explored the question of whether a high-density network can result in more realistic time series of annual 24-hour extreme precipitation amounts. They also looked at the possible impact of the variability and fluctuations of climate, since standard sources assume a static climate. Study areas included Minneapolis and St. Paul, and an area west of Duluth, Minnesota, near Hibbing. The following highlights study conclusions: * The spatial variability of the design values estimated for 20 km by 20 km is far too great to make that approach practical. * Based on the experience with the Hibbing study area, it is likely that the density of observations over large parts of the state would be too small to allow using 10 km by 10 km or 20 km by 20 km areas. * If the purpose of the design values is to provide guidance on extreme precipitation likely to be experienced a point, the current standard sources underestimate the values about one inch for a 24-hour duration and 100-year return period. * If the purpose of the design values is to provide guidance on extreme precipitation likely to be experienced at some point over an area, the current standard sources greatly underestimate the values. * There are no long-term trends in the magnitude of extreme precipitation events.