2026-09-26T01:18:40Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/127380 2026-02-03 col_2142_5131 col_2142_14770 com_2142_5130 com_2142_3518 com_2142_234

application/pdf en text Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2026-12-01 The student, Sean Matus, accepted the attached license on 2024-12-02 at 11:06. The student, Sean Matus, submitted this Dissertation for approval on 2024-12-02 at 11:19. This Dissertation was approved for publication on 2024-12-02 at 13:46. DSpace SAF Submission Ingestion Package generated from Vireo submission #21438 on 2025-03-28 at 14:43:35 Investigating the role of the land surface in modulating the Great Plains low-level jet Matus, Sean A. 2024-12-02 Dominguez, Francina Dominguez, Francina Kumar, Praveen Trapp, Robert J Ford, Trent W Low-level Jets Land-atmosphere Interactions Soil Moisture Subseasonal-to-seasonal Prediction eng The warm season in the United States Great Plains (GP) is characterized by frequent nocturnal low-level jets (LLJs). The GPLLJ serves as a major mechanism of atmospheric moisture transport, contributing to severe weather and precipitation in the region. Additionally, the nocturnal wind maxima of GPLLJs are a resource for wind energy production throughout the GP. These hydrometeorological and socioeconomic implications motivate a better understanding of the GPLLJ to improve predictability. It is accepted that a combination of atmospheric and land surface forcing modulates GPLLJ diurnal variability. While previous studies have examined the diurnal variability of soil moisture associated with GPLLJs, this is the first analysis at the subseasonal timescale. This thesis is the first documented evidence of a subseasonal timescale embedded within GPLLJ intensity that covaries with soil moisture over the U.S. Great Plains. I show that, due to the memory of the land surface, longer time scale variability associated with surface moisture affects GPLLJ intensity through a chain of land-atmosphere processes. Through a combined observational and statistical framework, this dissertation addresses the following questions on subseasonal GPLLJ variability: 1. What are the land and atmosphere conditions, at the diurnal, synoptic/pentad, and subseasonal timescales, antecedent to extreme GPLLJ events? 2. What physical mechanisms lead to stronger GPLLJ when dry soil moisture anomalies prevail over the southern Great Plains? 3. Can the temporal scales embedded within GPLLJ variability be disentangled to extract the subseasonal variability and link to soil moisture variability? The work starts with the first documented study of antecedent, subseasonal soil moisture anomalies associated with GPLLJs. We then present mechanistic evidence of how dry soil moisture anomalies can contribute to stronger GPLLJs. Our findings suggest that subseasonal dry soil moisture anomalies modulate GPLLJ intensity through warmer near surface temperatures, deepening of the planetary boundary layer, and stronger ageostrophic winds at sunset, all leading to nocturnal supergeostrophic winds through the Blackadar inertial oscillation. We lastly disentangle the different timescales of GPLLJ variability to extract the embedded land surface-driven subseasonal timescale with Multichannel Singular Spectrum Analysis. Our findings show that reconstructing the GPLLJ without the subseasonal variability, which is strongly linked to soil moisture, leads to underestimated wind speeds during dry periods and overestimated during wet. These findings quantitatively demonstrate how the land surface plays an important role in modulating GPLLJ intensity which can have major implications for improving subseasonal predictability of GPLLJ activity, and subsequent energy production and precipitation. 2024-12 Thesis https://hdl.handle.net/2142/127380 Copyright 2024 Sean A. Matus Civil & Environmental Eng Environ Engr in Civil Engr University of Illinois at Urbana-Champaign Ph.D. Dissertation