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Title: Characteristics of Bay of Bengal Monsoon Depressions in the 21st Century

Here, we show that 21st century increase in radiative forcing does not significantly impact the frequency of South Asian summer monsoon depressions (MDs) or their trajectories in the Coupled Model Intercomparison Project Phase 5 general circulation models (GCMs). A significant relationship exists between the climatological occurrences of MDs and the strength of the background upper (lower) tropospheric meridional (zonal) winds and tropospheric moisture in the core genesis region of MDs. Likewise, there is a strong relationship between the strength of the meridional tropospheric temperature gradient in the GCMs and the trajectories of MDs over land. While monsoon dynamics progressively weakens in the future, atmospheric moisture exhibits a strong increase, limiting the impact of changes in dynamics on the frequency of MDs. Moreover, the weakening of meridional tropospheric temperature gradient in the future is substantially weaker than its inherent underestimation in the GCMs. Our results also indicate that future increases in the extreme wet events are dominated by nondepression day occurrences, which may render the monsoon extremes less predictable in the future.
Authors:
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ;  [3] ;  [4] ; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Indian Institute of Technology Bombay, Mumbai (India)
  4. Univ. of Reading, Reading (United Kingdom)
Publication Date:
Grant/Contract Number:
AC05-00OR22725; AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 45; Journal Issue: 13; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; monsoon depression; climate change; South Asian monsoon
OSTI Identifier:
1474867
Alternate Identifier(s):
OSTI ID: 1459445

Rastogi, Deeksha, Ashfaq, Moetasim, Leung, L. Ruby, Ghosh, Subimal, Saha, Anamitra, Hodges, Kevin, and Evans, Katherine J.. Characteristics of Bay of Bengal Monsoon Depressions in the 21st Century. United States: N. p., Web. doi:10.1029/2018GL078756.
Rastogi, Deeksha, Ashfaq, Moetasim, Leung, L. Ruby, Ghosh, Subimal, Saha, Anamitra, Hodges, Kevin, & Evans, Katherine J.. Characteristics of Bay of Bengal Monsoon Depressions in the 21st Century. United States. doi:10.1029/2018GL078756.
Rastogi, Deeksha, Ashfaq, Moetasim, Leung, L. Ruby, Ghosh, Subimal, Saha, Anamitra, Hodges, Kevin, and Evans, Katherine J.. 2018. "Characteristics of Bay of Bengal Monsoon Depressions in the 21st Century". United States. doi:10.1029/2018GL078756.
@article{osti_1474867,
title = {Characteristics of Bay of Bengal Monsoon Depressions in the 21st Century},
author = {Rastogi, Deeksha and Ashfaq, Moetasim and Leung, L. Ruby and Ghosh, Subimal and Saha, Anamitra and Hodges, Kevin and Evans, Katherine J.},
abstractNote = {Here, we show that 21st century increase in radiative forcing does not significantly impact the frequency of South Asian summer monsoon depressions (MDs) or their trajectories in the Coupled Model Intercomparison Project Phase 5 general circulation models (GCMs). A significant relationship exists between the climatological occurrences of MDs and the strength of the background upper (lower) tropospheric meridional (zonal) winds and tropospheric moisture in the core genesis region of MDs. Likewise, there is a strong relationship between the strength of the meridional tropospheric temperature gradient in the GCMs and the trajectories of MDs over land. While monsoon dynamics progressively weakens in the future, atmospheric moisture exhibits a strong increase, limiting the impact of changes in dynamics on the frequency of MDs. Moreover, the weakening of meridional tropospheric temperature gradient in the future is substantially weaker than its inherent underestimation in the GCMs. Our results also indicate that future increases in the extreme wet events are dominated by nondepression day occurrences, which may render the monsoon extremes less predictable in the future.},
doi = {10.1029/2018GL078756},
journal = {Geophysical Research Letters},
number = 13,
volume = 45,
place = {United States},
year = {2018},
month = {6}
}