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Title: Sources of Intermodel Spread in the Lapse Rate and Water Vapor Feedbacks

Abstract

Sources of intermodel differences in the global lapse rate (LR) and water vapor (WV) feedbacks are assessed using CO 2 forcing simulations from 28 general circulation models. Tropical surface warming leads to significant warming and moistening in the tropical and extratropical upper troposphere, signifying a nonlocal, tropical influence on extratropical radiation and feedbacks. Model spread in the locally defined LR and WV feedbacks is pronounced in the Southern Ocean because of large-scale ocean upwelling, which reduces surface warming and decouples the surface from the tropospheric response. The magnitude of local extratropical feedbacks across models and over time is well characterized using the ratio of tropical to extratropical surface warming. It is shown that model differences in locally defined LR and WV feedbacks, particularly over the southern extratropics, drive model variability in the global feedbacks. The cross-model correlation between the global LR and WV feedbacks therefore does not arise from their covariation in the tropics, but rather from the pattern of warming exerting a common control on extratropical feedback responses. Because local feedbacks over the Southern Hemisphere are an important contributor to the global feedback, the partitioning of surface warming between the tropics and the southern extratropics is a key determinantmore » of the spread in the global LR and WV feedbacks. It is also shown that model Antarctic sea ice climatology influences sea ice area changes and southern extratropical surface warming. In conclusion, as a result, model discrepancies in climatological Antarctic sea ice area have a significant impact on the intermodel spread of the global LR and WV feedbacks.« less

Authors:
 [1];  [2];  [3];  [1];  [1];  [3]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Univ. of Washington, Seattle, WA (United States). Dept. of Atmospheric Sciences, and School of Oceanography
  3. Univ. of Washington, Seattle, WA (United States). Dept. of Atmospheric Sciences
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE; National Science Foundation (NSF); National Aeronautic and Space Administration (NASA)
OSTI Identifier:
1438795
Report Number(s):
LLNL-JRNL-739332
Journal ID: ISSN 0894-8755
Grant/Contract Number:
AC52-07NA27344; NNX13AN49G
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Climate
Additional Journal Information:
Journal Volume: 31; Journal Issue: 8; Journal ID: ISSN 0894-8755
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; Climate change; Climate sensitivity; Climate models

Citation Formats

Po-Chedley, Stephen, Armour, Kyle C., Bitz, Cecilia M., Zelinka, Mark D., Santer, Benjamin D., and Fu, Qiang. Sources of Intermodel Spread in the Lapse Rate and Water Vapor Feedbacks. United States: N. p., 2018. Web. doi:10.1175/JCLI-D-17-0674.1.
Po-Chedley, Stephen, Armour, Kyle C., Bitz, Cecilia M., Zelinka, Mark D., Santer, Benjamin D., & Fu, Qiang. Sources of Intermodel Spread in the Lapse Rate and Water Vapor Feedbacks. United States. doi:10.1175/JCLI-D-17-0674.1.
Po-Chedley, Stephen, Armour, Kyle C., Bitz, Cecilia M., Zelinka, Mark D., Santer, Benjamin D., and Fu, Qiang. Fri . "Sources of Intermodel Spread in the Lapse Rate and Water Vapor Feedbacks". United States. doi:10.1175/JCLI-D-17-0674.1. https://www.osti.gov/servlets/purl/1438795.
@article{osti_1438795,
title = {Sources of Intermodel Spread in the Lapse Rate and Water Vapor Feedbacks},
author = {Po-Chedley, Stephen and Armour, Kyle C. and Bitz, Cecilia M. and Zelinka, Mark D. and Santer, Benjamin D. and Fu, Qiang},
abstractNote = {Sources of intermodel differences in the global lapse rate (LR) and water vapor (WV) feedbacks are assessed using CO2 forcing simulations from 28 general circulation models. Tropical surface warming leads to significant warming and moistening in the tropical and extratropical upper troposphere, signifying a nonlocal, tropical influence on extratropical radiation and feedbacks. Model spread in the locally defined LR and WV feedbacks is pronounced in the Southern Ocean because of large-scale ocean upwelling, which reduces surface warming and decouples the surface from the tropospheric response. The magnitude of local extratropical feedbacks across models and over time is well characterized using the ratio of tropical to extratropical surface warming. It is shown that model differences in locally defined LR and WV feedbacks, particularly over the southern extratropics, drive model variability in the global feedbacks. The cross-model correlation between the global LR and WV feedbacks therefore does not arise from their covariation in the tropics, but rather from the pattern of warming exerting a common control on extratropical feedback responses. Because local feedbacks over the Southern Hemisphere are an important contributor to the global feedback, the partitioning of surface warming between the tropics and the southern extratropics is a key determinant of the spread in the global LR and WV feedbacks. It is also shown that model Antarctic sea ice climatology influences sea ice area changes and southern extratropical surface warming. In conclusion, as a result, model discrepancies in climatological Antarctic sea ice area have a significant impact on the intermodel spread of the global LR and WV feedbacks.},
doi = {10.1175/JCLI-D-17-0674.1},
journal = {Journal of Climate},
number = 8,
volume = 31,
place = {United States},
year = {Fri Mar 23 00:00:00 EDT 2018},
month = {Fri Mar 23 00:00:00 EDT 2018}
}

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