Publication Date

2022

Document Type

Dissertation/Thesis

First Advisor

Song, Jie

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Earth, Atmosphere and Environment

Abstract

Soil moisture stimulates land-atmosphere interactions by modifying energy and water fluxes in the boundary layer and it plays an important role in climate change studies. The objective of this research is to quantify the spatial and temporal variations of the Illinois Climate Network’s (ICN) observed topsoil moisture, as well as evaluate how accurately the new climate model, E3SM, is simulating soil moisture compared to the observed data during 2003-2014. Observed topsoil moisture averaged over growing season during the 12-year period indicates a general dry-north and wet-south pattern in Illinois, and northeast and southwest become drier with the progression of the growing season. During the 12-year period, most of the observation sites show an increasing trend in topsoil moisture over the growing season despite that these positive trends are significant at only a few sites. Despite a consistent dry bias during the growing season over Illinois, the E3SM model simulated the seasonal soil moisture variation very well, the simulated average moisture depletion between spring and summer is 0.164 water fraction by volume (wfv), comparable with the observed depletion 0.173 wfv. The E3SM also successfully simulated a soil moisture decrease of 0.5% in a drought year and an increase of 6% in a wet year, but the magnitude of these variations is much less than the observed decrease of 19% and increase of 12% in the corresponding drought and wet year. It suggests that improvement in the model should be on expanding the interannual variability to reduce the wet bias in the dry year and dry bias in the wet year. The modeled topsoil moisture averaged in the growing season also indicates an increasing trend as found in the observation during the 12-year period although most of the trends are nonsignificant. The modeled topsoil moisture in the southern Illinois is largely underestimated during the growing season, and it is suggested to incorporate the soil moisture regimes to account for accurate soil texture and to incorporate ecoregions’ description to improve the temporal and spatial variabilities in the modeled soil moisture.

Extent

68 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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