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

Journal Article · Mon Jul 16 00:00:00 EDT 2018 · Geophysical Research Letters

DOI:https://doi.org/10.1029/2018GL078756· OSTI ID:1706700

Rastogi, Deeksha ^[1]; Ashfaq, Moetasim ^[1]; Leung, Lai-Yung  ^[2]; Ghosh, Subimal ^[3]; Saha, Anamitra ^[3]; Hodges, Kevin ^[4]; Evans, Kate ^[1]

---

1. Oak Ridge National Laboratory
2. BATTELLE (PACIFIC NW LAB)
3. Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai
4. University of Reading

The controversy surrounding the observed trends in the frequency of South Asian Monsoon Depressions (MDs)1-4, the association of MDs with the summer season extremes5,6, and a moisture driven future precipitation response in Global Climate Models (GCMs)7,8 have elevated the importance of understanding climate change impacts on the characteristics of MDs. GCMs exhibit a significant relationship between the long-term mean occurrences of MDs and the strength of the background upper (lower) tropospheric meridional (zonal) winds and atmospheric moisture in the core genesis region of MDs. Likewise, the strength of the meridional tropospheric temperature gradient (MTG) in GCMs determines the trajectories of MDs over land. While monsoon dynamics progressively weakens in the future period, atmospheric moisture exhibits a strong increase, limiting the impact of changes in background dynamics on the frequency of MDs. Moreover, the weakening of the future MTG is many times weaker than its inherent underestimation in the GCMs. Hence the 21st century increase in radiative forcing does not significantly reduce the frequency of MDs or impact their trajectories over land in the GCMs. Although more wet extremes are expected to occur during the MD lifecycle, non-depression day extremes dominate the overall increase in extreme precipitation, which may render the monsoon extremes less predictable in the future.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1706700
• Report Number(s): PNNL-SA-126414
• Journal Information: Geophysical Research Letters, Vol. 45, Issue 13
• Country of Publication: United States
• Language: English