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

TitleCharacteristics of Bay of Bengal Monsoon Depressions in the 21st Century
Publication TypeJournal Article
Year of Publication2018
Date Published07/2018
Abstract / Summary

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 weaken 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 the 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 non-depression day occurrences, which may render the monsoon extremes less predictable in the future.

DOI10.1029/2018GL078756
Year of Publication: 2018
Date Published: 07/2018

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 weaken 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 the 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 non-depression day occurrences, which may render the monsoon extremes less predictable in the future.

DOI: 10.1029/2018GL078756
Citation:
Rastogi, D, M Ashfaq, L Leung, S Ghosh, A Saha, K Hodges, and K Evans.  2018.  "Characteristics of Bay of Bengal Monsoon Depressions in the 21st Century."  https://doi.org/10.1029/2018GL078756.