東華大學圖書館 |

Does It Hold Water? New Insights into the Stratospheric Water Vapor Feedback.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Does It Hold Water? New Insights into the Stratospheric Water Vapor Feedback./
作者:	Bourguet, Stephen.
面頁冊數:	1 online resource (146 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
標題:	Atmospheric sciences. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30488979click for full text (PQDT)
ISBN:	9798379610999

Does It Hold Water? New Insights into the Stratospheric Water Vapor Feedback.
Bourguet, Stephen.

Does It Hold Water? New Insights into the Stratospheric Water Vapor Feedback. - 1 online resource (146 pages)

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Thesis (Ph.D.)--Harvard University, 2023.

Includes bibliographical references

A robust feature of climate and chemistry models forced with projected anthropogenic greenhouse gas emissions is an increase in the water vapor concentration of the lower stratosphere. This projection has concerning implications for surface climate and stratospheric chemistry, yet the underlying mechanisms in these models have not been scrutinized. In particular, the coarse resolution of models and the parameterizations of small-scale processes that control water vapor concentrations at entry to the stratosphere may inhibit models from representing lower stratospheric water vapor in a warming climate. These concerns are amplified by the models' spread in the magnitude of their projections and their inability to reproduce historical observations. In this dissertation, I put aside the complexity of global climate models and explore mechanisms that can drive an increase in the water vapor content of the stratosphere following surface warming. I first revisit the Lagrangian trajectory method that has been used to study the dehydration of air parcels ascending to the lower stratosphere. By leveraging the high temporal and spatial resolution of a new reanalysis data product (ERA5), I calculate the biases that are introduced to the trajectories' temperature minima (i.e. the cold point) when they are computed with lower resolution input data. My main finding is that previous Lagrangian trajectory studies have underestimated the role of processes that are secondary to cold point temperatures in setting the water vapor concentration of the lower stratosphere, such as cloud microphysics and mixing. This work also informs future studies on how to select input data for trajectory calculations in accordance with the studies' error tolerance.I then advance my Lagrangian trajectory method to explore how changes to zonal and vertical wind speeds in the tropical upper troposphere and lower stratosphere will impact the dehydration of air parcels ascending to the lower stratosphere. I find that a deceleration of the Walker Circulation, manifest as a fractional decrease in the magnitude of zonal winds in the region of interest, leads to a warmer average cold point temperature for trajectories rising to the lower stratosphere. This would lead to stratospheric moistening according to the Clausius-Clapeyron relationship. I then show that warmer temperatures and slower winds near the cold point allow ice to grow larger and gravitationally settle greater distances prior to sublimation, which decreases but does not eliminate the overall moistening. Given that a slowdown of the Walker Circulation is a robust response of the tropospheric circulation to surface warming according to both models and theory, this constitutes a stratospheric water vapor feedback that does not require temperatures to warm near the tropopause.Finally, I identify a mechanism that will increase the cold point temperature following surface warming, which would have a first-order effect on lower stratospheric water vapor concentrations. Motivated by observations of constant ozone concentrations at the cold point across seasons, which are unexpected given the seasonal fluctuations of the cold point's temperature and height, I construct an ozone budget for air parcels ascending to the cold point. By using Lagrangian trajectories and ozone concentration and production profiles, I show that both the origin of air parcels that reach the cold point and the production that occurs along their paths are important for the ozone concentration at the cold point. As the surface warms, the troposphere will expand, pushing all processes that happen relative to the tropopause into a region of increased ozone production. This will increase the production of ozone for air parcels as they move into the lower stratosphere, and according to the ozone budget, this will increase ozone concentrations relative to the tropopause and result in a warmer cold point.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798379610999Subjects--Topical Terms:

3168354
Atmospheric sciences.
Subjects--Index Terms:

Climate feedbacksIndex Terms--Genre/Form:

542853
Electronic books.

Does It Hold Water? New Insights into the Stratospheric Water Vapor Feedback.
LDR:05316nmm a2200397K 4500 001 2363024
005 20231109104736.5
006 m o d
007 cr mn ---uuuuu
008 241011s2023 xx obm 000 0 eng d
020 $a 9798379610999
035 $a (MiAaPQ)AAI30488979
035 $a AAI30488979
040 $a MiAaPQ $b eng $c MiAaPQ $d NTU
100 1 $a Bourguet, Stephen. $3 3703770
245 1 0 $a Does It Hold Water? New Insights into the Stratospheric Water Vapor Feedback.
264 0 $c 2023
300 $a 1 online resource (146 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
338 $a online resource $b cr $2 rdacarrier
500 $a Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
500 $a Advisor: Linz, Marianna K.
502 $a Thesis (Ph.D.)--Harvard University, 2023.
504 $a Includes bibliographical references
520 $a A robust feature of climate and chemistry models forced with projected anthropogenic greenhouse gas emissions is an increase in the water vapor concentration of the lower stratosphere. This projection has concerning implications for surface climate and stratospheric chemistry, yet the underlying mechanisms in these models have not been scrutinized. In particular, the coarse resolution of models and the parameterizations of small-scale processes that control water vapor concentrations at entry to the stratosphere may inhibit models from representing lower stratospheric water vapor in a warming climate. These concerns are amplified by the models' spread in the magnitude of their projections and their inability to reproduce historical observations. In this dissertation, I put aside the complexity of global climate models and explore mechanisms that can drive an increase in the water vapor content of the stratosphere following surface warming. I first revisit the Lagrangian trajectory method that has been used to study the dehydration of air parcels ascending to the lower stratosphere. By leveraging the high temporal and spatial resolution of a new reanalysis data product (ERA5), I calculate the biases that are introduced to the trajectories' temperature minima (i.e. the cold point) when they are computed with lower resolution input data. My main finding is that previous Lagrangian trajectory studies have underestimated the role of processes that are secondary to cold point temperatures in setting the water vapor concentration of the lower stratosphere, such as cloud microphysics and mixing. This work also informs future studies on how to select input data for trajectory calculations in accordance with the studies' error tolerance.I then advance my Lagrangian trajectory method to explore how changes to zonal and vertical wind speeds in the tropical upper troposphere and lower stratosphere will impact the dehydration of air parcels ascending to the lower stratosphere. I find that a deceleration of the Walker Circulation, manifest as a fractional decrease in the magnitude of zonal winds in the region of interest, leads to a warmer average cold point temperature for trajectories rising to the lower stratosphere. This would lead to stratospheric moistening according to the Clausius-Clapeyron relationship. I then show that warmer temperatures and slower winds near the cold point allow ice to grow larger and gravitationally settle greater distances prior to sublimation, which decreases but does not eliminate the overall moistening. Given that a slowdown of the Walker Circulation is a robust response of the tropospheric circulation to surface warming according to both models and theory, this constitutes a stratospheric water vapor feedback that does not require temperatures to warm near the tropopause.Finally, I identify a mechanism that will increase the cold point temperature following surface warming, which would have a first-order effect on lower stratospheric water vapor concentrations. Motivated by observations of constant ozone concentrations at the cold point across seasons, which are unexpected given the seasonal fluctuations of the cold point's temperature and height, I construct an ozone budget for air parcels ascending to the cold point. By using Lagrangian trajectories and ozone concentration and production profiles, I show that both the origin of air parcels that reach the cold point and the production that occurs along their paths are important for the ozone concentration at the cold point. As the surface warms, the troposphere will expand, pushing all processes that happen relative to the tropopause into a region of increased ozone production. This will increase the production of ozone for air parcels as they move into the lower stratosphere, and according to the ozone budget, this will increase ozone concentrations relative to the tropopause and result in a warmer cold point.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
650 4 $a Atmospheric sciences. $3 3168354
650 4 $a Climate change. $2 bicssc $3 2079509
650 4 $a Aeronomy. $3 2102064
653 $a Climate feedbacks
653 $a Ozone
653 $a Stratosphere
653 $a Water vapor
653 $a Greenhouse gas emissions
655 7 $a Electronic books. $2 lcsh $3 542853
690 $a 0725
690 $a 0404
690 $a 0367
710 2 $a ProQuest Information and Learning Co. $3 783688
710 2 $a Harvard University. $b Earth and Planetary Sciences. $3 3168947
773 0 $t Dissertations Abstracts International $g 84-12B.
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30488979 $z click for full text (PQDT)