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Understanding soil moisture dynamics using observations and climate models
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TitleInfo
Title
Understanding soil moisture dynamics using observations and climate models
Name
(type = personal)
NamePart
(type = family)
Li
NamePart
(type = given)
Haibin
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Haibin Li
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author
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Robock
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Alan
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Advisory Committee
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Alan Robock
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chair
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Reinfelder
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Ying Fan
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Advisory Committee
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Ying Fan Reinfelder
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internal member
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Broccoli
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Anthony
Affiliation
Advisory Committee
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Anthony Broccoli
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internal member
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Milly
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Christopher
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Advisory Committee
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Christopher Milly
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outside member
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Rutgers University
Role
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degree grantor
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NamePart
Graduate School-New Brunswick
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school
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Text
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theses
OriginInfo
DateCreated
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2007
DateOther
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2007
Language
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(authority = ISO 639-3:2007);
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English
PhysicalDescription
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electronic
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application/pdf
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text/xml
Extent
xiii, 121 pages
Abstract
(type = abstract)
With the objective to improve our understanding of soil moisture and its long term changes, I analyzed and compared climate model simulations with in situ soil moisture observations. Three studies were conducted to investigate soil moisture variations on seasonal to interannual scales and its long term changes.
To investigate soil moisture evolutions on seasonal to interannual scales and the capacity of reanalysis systems to capture the observed characteristics, I analyzed newly updated 19 yr of Chinese soil moisture data and evaluated ERA40, NCEP/NCAR reanalysis (R-1), and NCEP/DOE reanalysis 2 (R-2). Over this region, soil moisture seasonality is in general not strong. Seasonal cycles and interannual variations exhibit considerably spatial diversity. R-2 generally exhibits improved interannual variability and better seasonal patterns of soil moisture than R-1 as a result of incorporating observed precipitation. ERA40 produces a better mean value of soil moisture for most Chinese stations and good interannual variability. In terms of temporal scale - an indicator of anomaly persistence, R-2 has a memory about twice that of the observations for the growing season. The unrealistic long temporal scale of R-2 can be attributed to the deep layer of the land surface model, which is too thick and dominates the soil moisture variability. The analysis highlights the importance of correct soil parameters to land surface processes and points out possible directions in which the reanalysis can be continuously improved to provide more realistic soil moisture outputs.
Observations from Ukraine and Russia show significant increases in summer for the period from 1958-1999 that seem contradictory to the classic summer drying issue from early modeling studies. To see whether the latest climate models can capture the observed patterns, I calculated trends in soil moisture simulations from Intergovernmental Panel on Climate Change Fourth Assessment climate models. The upward trends in observations, which cannot be explained by precipitation and temperature changes alone, were found to be much larger than most trends in model realizations. Solar dimming is proposed to have played an important role in modulating soil moisture variations for these two regions.
Further, a series off-line sensitivity experiments with a sophisticated land surface model were conducted to investigate possible contribution from solar dimming and elevated CO2 to the observed soil moisture trends for Ukraine and Russia. I demonstrate, by imposing a downward trend to shortwave radiation forcing to mimic the dimming, the observed soil moisture pattern can be essentially reproduced. On the other hand, the effects of elevated CO2 are relatively small for the study period. The results support the hypothesis that solar dimming may have played an important role in regional soil moisture changes.
To investigate soil moisture evolutions on seasonal to interannual scales and the capacity of reanalysis systems to capture the observed characteristics, I analyzed newly updated 19 yr of Chinese soil moisture data and evaluated ERA40, NCEP/NCAR reanalysis (R-1), and NCEP/DOE reanalysis 2 (R-2). Over this region, soil moisture seasonality is in general not strong. Seasonal cycles and interannual variations exhibit considerably spatial diversity. R-2 generally exhibits improved interannual variability and better seasonal patterns of soil moisture than R-1 as a result of incorporating observed precipitation. ERA40 produces a better mean value of soil moisture for most Chinese stations and good interannual variability. In terms of temporal scale - an indicator of anomaly persistence, R-2 has a memory about twice that of the observations for the growing season. The unrealistic long temporal scale of R-2 can be attributed to the deep layer of the land surface model, which is too thick and dominates the soil moisture variability. The analysis highlights the importance of correct soil parameters to land surface processes and points out possible directions in which the reanalysis can be continuously improved to provide more realistic soil moisture outputs.
Observations from Ukraine and Russia show significant increases in summer for the period from 1958-1999 that seem contradictory to the classic summer drying issue from early modeling studies. To see whether the latest climate models can capture the observed patterns, I calculated trends in soil moisture simulations from Intergovernmental Panel on Climate Change Fourth Assessment climate models. The upward trends in observations, which cannot be explained by precipitation and temperature changes alone, were found to be much larger than most trends in model realizations. Solar dimming is proposed to have played an important role in modulating soil moisture variations for these two regions.
Further, a series off-line sensitivity experiments with a sophisticated land surface model were conducted to investigate possible contribution from solar dimming and elevated CO2 to the observed soil moisture trends for Ukraine and Russia. I demonstrate, by imposing a downward trend to shortwave radiation forcing to mimic the dimming, the observed soil moisture pattern can be essentially reproduced. On the other hand, the effects of elevated CO2 are relatively small for the study period. The results support the hypothesis that solar dimming may have played an important role in regional soil moisture changes.
Note
(type = degree)
Ph.D.
Note
(type = bibliography)
Includes bibliographical references (p. 68-79).
Subject
(authority = RUETD)
Topic
Environmental Sciences
Subject
(authority = ETD-LCSH)
Topic
Soil moisture
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TitleInfo
Title
Graduate School - New Brunswick Electronic Theses and Dissertations
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rucore19991600001
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http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.13480
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ETD_147
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doi:10.7282/T3FF3ST1
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ETD doctoral
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Copyright protected
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Open
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Haibin Li
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Rutgers University. Graduate School-New Brunswick
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Non-exclusive ETD license
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Author Agreement License
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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