First Advisor
Paul Loikith
Term of Graduation
January 2025
Date of Publication
9-1-2025
Document Type
Thesis
Language
English
Subjects
Extreme Precipitation, k-means clustering, Seasonal variations, Synoptic-scale meteorological patterns
Physical Description
1 online resource ( pages)
Abstract
Seasonal and spatial variations of synoptic-scale weather patterns concurrent to extreme precipitation days, defined as days above the seasonal 95th percentile of the daily precipitation distribution, are characterized over a 44-year period (1980-2023) for the Contiguous United States (CONUS). Using atmospheric reanalysis data and a grid-cell centered approach, we construct seasonal anomaly composite patterns for sea level-pressure (SLP), integrated water vapor transport, 500 hPa geopotential height (Z500), and 300 hPa wind speed. Atmospheric variables known to be important for extreme precipitation. By interpolating composites for each grid cell onto the same polar coordinate grid relative to the grid cell we are able to directly compare composites from any grid cell with each other providing a comprehensive climatology of meteorological drivers of extreme precipitation across the entire CONUS for all four meteorological seasons. We describe results for winter and summer. A novel k-means clustering technique is employed to group standardized anomaly patterns to identify regions with similar pattern characteristics. Descriptive statistics to quantify pattern strength and correlation are computed as grid cell by grid cell metrics. The combination of these approaches helps to diagnose the average synoptic conditions associated with extreme precipitation in each season at all CONUS grid cells in an easily interpretable format. Results show that winter patterns associated with extreme precipitation are on average stronger than summer; and our patterns show height and pressure gradients aligned with enhanced vapor transport. We find that western US Z500 and SLP anomaly patterns associated with extreme precipitation tend not to have dipoles or to exhibit weak dipoles and that pressure patterns tend to be vertically stacked in the west. By contrast, we find that eastern US Z500 and SLP anomaly patterns have clear dipoles which is indicative of the east having stronger baroclinicity, and these patterns exhibit a tilt with height to the pressure gradients. Identified regions and circulation patterns vary by season. Results from the current study can be used as a baseline for understanding how well climate models simulate the synoptic-scale conditions that drive extreme precipitation and how and if meteorological patterns associated with extreme precipitation change in the future. Motivated by a desire to answer these climate and climate model questions, this methodology was created with a goal of extensibility to climate model data in future work.
Rights
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Recommended Citation
Johnson, Amy, "Synoptic-scale Meteorological Patterns Associated with Extreme Precipitation Over the Contiguous United States and Concomitant Seasonal and Regional Variability" (2025). Dissertations and Theses. Paper 6942.