Abstract
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.
| Original language | English |
|---|---|
| Pages (from-to) | 6637-6645 |
| Number of pages | 9 |
| Journal | Geophysical Research Letters |
| Volume | 45 |
| Issue number | 13 |
| DOIs | |
| State | Published - Jul 16 2018 |
Funding
We thank two anonymous reviewers for helpful and insightful comments. This work is supported by the Department of Energy Office of Science Biological and Environmental Research as part of the Regional and Global Climate Modeling program. Support for data storage and analysis is provided by the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory (ORNL), which is supported by the Office of Science of the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725. We thank U.S. DOE’s Program for Climate Model Diagnosis and Intercomparison for providing coordinating support and leading development of software infrastructure in partnership with the Global Organization for Earth System Science Portals for CMIP. All westward moving MD data sets used in this study are part of the supporting information. Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RL01830. Received 15 MAY 2018 Accepted 14 JUN 2018 Accepted article online 21 JUN 2018 Published online 7 JUL 2018 ©2018. American Geophysical Union. All Rights Reserved. This manuscript has been authored by UT-Battelle, LLC,under contract DE- AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-publicaccess-plan).
| Funders | Funder number |
|---|---|
| Department of Energy Office of Science Biological and Environmental Research | |
| U.S. Department of Energy | DE-AC05-00OR22725, DE-AC05-76RL01830 |
| Battelle | |
| Office of Science | |
| Oak Ridge National Laboratory |
Keywords
- South Asian monsoon
- climate change
- monsoon depression